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Organophosphates are the most widely used insecticide class in agriculture. The effects of organophosphates on insectivorous birds can potentially reduce the capacity of these birds to regulate insect pest populations as well as jeopardizing the survival of vulnerable bird species in matrix habitats. In this study, we investigated the diversity of birds inhabiting commercial macadamia orchards in Australia and assessed community-wide exposure of birds to an organophosphate insecticide (trichlorfon). We also studied the impact of trichlorfon on arthropods, and how this affected bird activity. We used a novel approach, combining bird acoustic surveys, and three different arthropod trapping devices. Birds and arthropods were surveyed immediately before and after a trichlorfon application, in sprayed and unsprayed orchards, at six different sites. Surveys showed that trichlorfon applications produced no changes in bird activity, either at the species or community level. Only one species (Lichmera indistincta) showed a significant increase in acoustic activity after treatment. These results indicate that several (62) bird species, some of which have been noted as undergoing regional decline, are exposed to trichlorfon applications. Additionally, trichlorfon applications also produced rapid, negative impacts on certain arthropod groups, particularly spiders. Because almost (80%) of the bird species recorded in the study include arthropods in their diets, then arthropod contaminated by trichlorfon are likely consumed by these orchard-dwelling birds. We recommend that pest management should incorporate strategies to reduce wildlife exposure to toxic chemicals to meet the joint goals of crop production and wildlife conservation in structurally complex agricultural habitats.

Global warming is often predicted to increase damage to plants through direct effects on insect herbivores. However, the indirect impacts of rising temperatures on herbivores, mediated through interactions with their biotic environment, could dampen these effects.Using a series of reciprocal density experiments with gravid females and developing nymphs, we examined interspecific competition between two coexisting phloem feeders Nilaparvata lugens (BPH) and Sogatella furcifera (WBPH), on rice at 25 and 30°C.WBPH performed better (i.e. adults survived longer, nymphs developed faster and grew larger) at 25°C and BPH (i.e. nymphs developed faster) at 30°C. However, contrary to predictions, WBPH had a greater effect in reducing oviposition and nymph performance in BPH at 30°C.A decoupling of resource use by WBPH and its antagonistic effects on BPH at the higher temperature suggests that WBPH feeding induces host defences that reduce BPH fitness (i.e. interference competition). Meanwhile, BPH facilitated WBPH oviposition at 30°C and facilitated WBPH nymph performance at 25 and 30°C. Greater facilitation of feeding in WBPH nymphs by BPH at high densities suggests that mechanical damage and host responses to damage increased the fitness of the heterospecific nymphs.Although BPH also facilitated egg‐laying by WBPH, intra‐ and interspecific crowding countered this facilitation at both temperatures. Simulated life tables for planthoppers at 25 and 30°C depicted significantly lower offspring numbers on rice infested by WBPH alone and from mixed BPH‐WBPH infestations than from infestations by BPH alone.Our results indicate how interference competition—mediated through host plant defences—can increase ecosystem resilience to the warmer temperatures predicted under global climate change. A free Plain Language Summary can be found within the Supporting Information of this article., A free Plain Language Summary can be found within the Supporting Information of this article.

The brown planthopper, Nilaparvata lugens (Stål), is a key challenge to rice production in Asia. Outbreaks of planthoppers are associated with excessive fertilizer applications, consequently, we examined planthopper interactions with susceptible, tolerant and resistant varieties of rice under varying levels of soil nitrogen in a greenhouse experiment. We compared planthopper fitness (survival × reproduction) and plant tolerance (functional plant loss index) for 16 varieties at 0, 80 and 150 Kg added nitrogen ha−1. The planthoppers grew larger, developed more quickly and laid more eggs on susceptible varieties, compared with the resistant and tolerant varieties. Moreover, soil nitrogen generally increased planthopper fitness on resistant varieties, but relative resistance was maintained. Functional plant loss was highest among the susceptible varieties, but weight and growth rate reductions per mg of planthopper were often highest in the tolerant varieties. Tolerance was associated with large, fast-growing plants, with at least moderate resistance to the planthopper. Susceptibility was associated with a small size and/or an absence of resistance genes. Our results suggested that early-tillering rice plants can be both resistant and tolerant to the brown planthopper, but cannot be both susceptible and tolerant of planthoppers at high densities. This indicates that at least moderate resistance is required for tolerance against this herbivore. Furthermore, although dwarf varieties had a low tolerance of planthoppers, they could express resistance through functioning resistance genes.

The adaptation by planthoppers to feed and develop on resistant rice is a challenge for pest management in Asia. We conducted a series of manipulative experiments with the brown planthopper (Nilaparvata lugens (Stål)) on the resistant rice variety IR62 (BPH3/BPH32 genes) to assess behavioral and bionomic changes in planthoppers exhibiting virulence adaptation. We also examined the potential role of yeast-like symbionts (YLS) in virulence adaptation by assessing progeny fitness (survival × reproduction) following controlled matings between virulent males or females and avirulent males or females, and by manipulating YLS densities in progeny through heat treatment. We found virulence-adapted planthoppers developed faster, grew larger, had adults that survived for longer, had female-biased progeny, and produced more eggs than non-selected planthoppers on the resistant variety. However, feeding capacity—as revealed through honeydew composition—remained inefficient on IR62, even after 20+ generations of exposure to the resistant host. Virulence was derived from both the male and female parents, however, females contributed more than males to progeny virulence. We found that YLS are essential for normal planthopper development and densities are highest in virulent nymphs feeding on the resistant host, however, we found only weak evidence that YLS densities contributed more to virulence. Virulence against IR62 in the brown planthopper, therefore, involves a complex of traits that encompass a series of behavioral, physiological, and genetic mechanisms, some of which are determined only by the female parent.

The microbiomes of phloem‐feeding insects include functional bacteria and yeasts essential for herbivore survival and development. Changes in microbiome composition are implicated in virulence adaptation by herbivores to host plant species or host populations (including crop varieties). We examined patterns in adaptation by the green leafhopper, Nephotettix virescens, to near‐isogenic rice lines (NILs) with one or two resistance genes and the recurrent parent T65, without resistance genes. Only the line with two resistance genes was effective in reducing leafhopper fitness. After 20 generations on the resistant line, selected leafhoppers attained similar survival, weight gain, and egg laying to leafhoppers that were continually reared on the susceptible recurrent parent, indicating that they had adapted to the resistant host. By sequencing the 16s rRNA gene, we described the microbiome of leafhoppers from colonies associated with five collection sites, and continually reared or switched between NILs. The microbiomes included 69–119 OTUs of which 44 occurred in ≥90% of samples. Of these, 14 OTUs were assigned to the obligate symbiont Candidatus sulcia clade. After 20 generations of selection, collection site had a greater effect than host plant on microbiome composition. Six bacteria genera, including C. sulcia, were associated with leafhopper virulence. However, there was significant within‐treatment, site‐related variability in the prevalence of these taxa such that the mechanisms underlying their association with virulence remain to be determined. Our results imply that these taxa are associated with leafhopper nutrition. Ours is the first study to describe microbiome diversity and composition in rice leafhoppers. We discuss our results in light of the multiple functions of herbivore microbiomes during virulence adaptation in insect herbivores., We describe the microbiome of leafhoppers from colonies associated with five collection sites and continually reared, or switched between near‐isogenic rice lines with resistance genes. The microbiomes included 69–119 OTUs of which 44 occurred in ≥90% of samples. Six bacteria genera, including Candidatus sulcia, were associated with leafhopper virulence. Ours is the first study to describe microbiome diversity and composition in rice leafhoppers.

Two stem-boring moths, the yellow stemborer (YSB) Scirpophaga incertulas (Walker), and the striped stemborer (SSB), Chilo suppressalis (Walker), damage rice in Asia. YSB is the dominant species in much of tropical Asia. Both species are oligophagous on domesticated and wild rice. We investigated the roles of host plant preferences and larval performance in determining the larval densities of both species in rice plots. In screenhouse experiments, YSB showed significant preference–performance coupling. Adults preferred high-tillering rice varieties during early vegetative growth. In contrast, SSB did not demonstrate oviposition preferences under the same screenhouse conditions, but did oviposit less on the wild rice Oryza rufipogon Griff. than on domesticated rice varieties during a choice experiment. Despite differences in preference–performance coupling, larval survival and biomass across 10 varieties were correlated between the two species. YSB and SSB larvae occurred in relatively high numbers on rice varieties with large tillers (IR70, IR68, and T16) in wet and dry season field experiments. However, whereas YSB was the dominant species on IR68 and IR70, it was relatively less abundant on T16, where SSB dominated. Results suggest that YSB preferentially attacked fast-growing rice varieties with high tiller numbers early in the crop cycle. Meanwhile SSB, which has weak preference–performance coupling, occurred in rice plants with large tillers that were relatively free of YSB later in the crop cycle. These factors may allow the species to coexist. We discuss the implications of proximate and ultimate factors influencing stemborer co-occurrence for the sustainable production of rice in tropical Asia.

Host plant resistance has received considerable attention for the management of insect herbivores on crop plants. However, resistance is threatened by the rapid adaptation of target herbivores towards virulence (the ability to survive, develop and damage a host with major resistance genes). This study examines the potential costs and benefits of adaptation for virulence in herbivores. We continuously reared planthoppers, Nilaparvata lugens, on two susceptible and three resistant rice, Oryza sativa, varieties for 20 + generations. We then assessed the performance of selected planthoppers across a range of rice lines with distinct resistance genes. We found that planthoppers with long-term exposure to resistant hosts (particularly IR62 with the Bph3(t) and BPH32 gene loci, and PTB33 with the Bph3(t), BPH32 and BPH26 gene loci) gained virulence against related varieties with the same and different resistance genes, but planthoppers adapted to the resistant host IR65482-4-136-2-2 (BPH10 locus) had reduced performance on phylogenetically distant plants with distinct resistant genes. In choice bioassays, avirulent planthoppers showed marked preferences for susceptible lines, whereas virulent planthoppers were less selective of varieties. We also examined whether virulence was associated with insecticide susceptibility. We tested susceptibility to three insecticides using a topical application method. Populations selectively reared on IR65482-4-136-2-2 had increased susceptibility to imidacloprid and fipronil, representing a possible trade-off with virulence. In contrast, a population with virulence to the highly resistant variety PTB33 was 4.88 × more resistant to imidacloprid and 3.18 × more resistant to BPMC compared to planthoppers of the same origin but reared on the susceptible variety IR22. Our results suggest complex relations between insecticide resistance and virulence that vary according to insecticidal toxins and resistance genes, and include potentially increased insecticide-susceptibility (a trade-off) as well as common detoxification mechanisms (a benefit)., Graphical abstract Image 1, Highlights • Costs and benefits of Nilaparvata lugens adaptation to resistant rice are assessed. • N. lugens selected on IR65482-4-136-2-2 had reduced performance on other hosts. • N. lugens selected on PTB33 and IR62 gained virulence against other resistant hosts. • Virulence against IR65482-4-136-2-2 was associated with insecticide susceptibility. • Virulence against PTB33 was associated with resistance to two insecticides.

The establishment of cattle ranches throughout the world has prompted the release of dung beetles as biological control agents that reduce pasture fouling and control dung-breeding flies. One of these beetles, Digitonthophagus gazella (Fabricius) (Coleoptera: Scarabaeidae), that is native to southeast Africa, has been introduced into the Americas, Australia, and New Zealand. Distribution records for this species have been used to develop climate models of potential future establishment. Recent studies, however, identify D. gazella as a complex of seven species. Taking into account this revision, and the clear identification of the records belonging to the actual D. gazella, we developed environmental models to identify factors that have contributed to the establishment of this species across regions and habitats. We compared the environmental conditions of D. gazella in its native range against those in the regions where the species has or has not established. Our results indicate that D. gazella is still absent in certain parts of Central and South America and parts of Africa where it could potentially establish. We speculate that its distribution in Africa is limited by competitive exclusion. The introduction of D. gazella in America is relatively recent, such that the full extent of its distribution has probably yet to be realized. In Australia and North America, D. gazella is present in regions not predicted according to its native environmental conditions. This discrepancy may reflect a lack of competitive exclusion, phenotypic plasticity, and/or genetic adaptation. Our analyses suggest that the species has the ability to adapt to a wide range of environmental conditions that are extremely different from those in their native region. The species represents a useful case study to indicate that an introduced species may expand its realized niche beyond what is expected based on apparent environmental limits in the species native range.

We provide a case study where Integrated Pest Management (IPM) for rice production systems has been introduced to the Greater Mekong Subregion (GMS). Funded by the European Union (EU), this IPM initiative brought together local and international partners to develop an environmentally friendly and economically sustainable rice pest management strategy for southwestern China, Laos, and Myanmar. A key component of the strategy was to establish 12 Trichogramma spp. rearing facilities (TRFs) that mainly targeted rice stem borers. Four TRFs were established in each of the participating countries. The most promising strains of Trichogramma chilonis (Ishii) and T. japonicus (Ashmead) were selected for production in the TRFs based on extensive field surveys as well as laboratory and field release studies. The project also considered the potential for Trichogramma spp. of each strain to withstand the high temperatures expected under a changing climate. Implementation of the IPM strategy resulted in higher rice yields (2–10%), an increase in natural enemy abundance (e.g., twice as many spiders), and a reduction in insecticide applications (1.5 fewer applications). During a capacity-building program, IPM practices with strong cultural and biological control-based components were promoted among ca 50 IPM trainers and ca 6,400 rice farmers. This case study indicates the potential successes of advanced biological control-based IPM systems. We believe that these systems merit wider consideration, including adaptations for other regions and crops.

This review examines the effects of crop management on the efficiency and durability of planthopper resistant rice in Asia. Historical evidence and selection experiments indicate that the proportion of virulent individuals in planthopper populations is normally sufficiently high for populations to overcome major resistance genes within 12–15 generations. Pyramiding resistance may prolong durability, but will depend on avoiding concurrent deployment of monogenic and pyramided lines that share resistance genes, and on the capacity of planthoppers to maintain virulence to ≥2 genes. Combining major genes with quantitative resistance will increase durability. Planthopper population size is likely to be the main contributor to virulence adaptation during the early stages of varietal adoption. High fertilizer inputs increase the availability of soluble proteins, thereby increasing rice susceptibility to planthoppers. Resurgence insecticides can directly increase host plant susceptibility, increase planthopper fecundity, and/or deplete natural enemy abundance, leading to rapid increases in planthopper densities. Nevertheless, comparative experiments indicate that the relative fitness of planthoppers on resistant and susceptible varieties is often maintained across gradients of fertilizer and insecticide applications. However, densities of planthoppers will increase in response to high inputs thereby enhancing the potential for populations to overcome resistance. Avoiding excessive fertilizer applications and resurgence insecticides, rotating rice varieties, increasing rice genetic diversity in the landscape, and maintaining generalist natural enemies will slow planthopper population growth, enhance resistance and has the potential to prolong durability. Because insecticides reduce the profitability of using resistant varieties, host plant resistance must be accompanied by a concomitant decline in insecticide use if it is to achieve its goals as an efficient, economic and environmentally friendly pest management option.

Decomposition is a key ecosystem service that reduces non-living organic matter, returning nutrients to the soil. In this study, we examine the responses by fly (Diptera) communities to molluscicide-poisoned apple snail (Pomacea canaliculata) cadavers in a tropical rice production landscape. Fewer molluscicide-poisoned cadavers were colonised by decomposer flies (niclosamide = 61% of cadavers with fly larvae; methaldehyde = 53%; Camellia sp. seed extract [saponin] = 50%) compared to control (freezer-killed) cadavers (81%). Metaldehyde, niclosamide and saponin reduced the abundance (average 51% reduction), biomass-density (average 63% reduction) and species richness (average 38% reduction) of flies emerging from the snail cadavers. The decay of control cadavers was generally faster (57% more tissue removed over 3 days) than molluscicide-treated cadavers. We suggest that poisoned carcasses potentially affect ecological communities across a range of trophic levels.

The diversification of farming landscapes is proposed as a method to increase farm productivity while at the same time enhancing pest regulation services provided by the natural enemies of insect herbivores. In this study, areas of diversified and conventional rice fields (with 2–14 fields per area = 0.42–1.31 ha) were established at three sites in the Philippines. The diversified areas had a series (> 40 per hectare) of small (

Invasive Alien Species (IAS) can become a tremendous burden to national economies; however, few studies have quantified the economic impacts of IAS, particularly for developing nations. The golden apple snail, Pomacea canaliculata (Lamarck), was introduced into Ecuador in 2005. By 2012, the snail had affected 94% of Ecuador's rice-growing areas. We used government surveys of rice production and snail distributions, as well as yearly production costs and rice prices, to estimate snail-associated losses to rice productivity and profitability between 2005 and 2015 – the first decade of P. canaliculata in Ecuador. Based on the intensity of the invasion and changing management practices, we estimate that the golden apple snail caused accumulated losses of 35.65 K tons of rice grain (worth US$23.10 M) with further productivity losses (lost inputs and labour) of US$9.61 M (total = US$32.71 M), until 2015. Based on survey information, we estimate that 90% of affected fields were treated with pesticides during the 5 years following initial establishment of the snail on individual rice farms. Pesticides potentially saved up to $10 M in damage during peak snail densities in 2012. By 2015, prophylactic molluscicide treatments were costing the nation US$15.24 M annually (including application costs: accumulated 10-year cost = $123.46 M, assuming 90% coverage). Increasing pesticide and labour costs, but relatively stable farm-gate rice prices, suggest that the continued chemical control of golden apple snail in Ecuador is economically unsustainable. We discuss possible alternatives to prophylactic molluscicide applications that can increase the economic and environmental sustainability of rice production in the face of high densities of apple snails during post-introduction outbreaks. We suggest that nations at high risk from invasive apple snails (e.g., Bangladesh, India, Colombia and Peru) could avoid substantial losses by pre-emptively researching and adopting mechanized crop establishment practices that not only reduce labour costs, but also prevent potential damage from apple snails to rice.

The standard seedling seedbox test (SSST) is the most prevalent phenotyping test in research on the genetics and breeding of planthopper-resistant rice. Using 16 rice lines that included plants susceptible, resistant and tolerant to the brown planthopper (Nilaparvata lugens), we compared the SSST to modified seedling seedbox tests (MSSTs) and the days-to-wilt (DTW) test. We also conducted a series of performance tests to assess nymph survival and development, adult longevity and egg-laying, egg survival, honeydew production, and plant weight loss. We also assessed the relative costs of the different phenotyping tests to better recommend test protocols that are suitable for high-throughput phenotyping. The SSST was found to be highly robust but fails to identify late-stage resistance, tolerance, or ovicidal responses. MSSTs improved phenotyping by identifying plants with low damage from planthoppers at later growth stages. Herbivore performance tests such as population or biomass build-up tests reduce space requirements and reduce setup and evaluation costs compared with bulk tests. They can also facilitate the assessment of plant tolerance, albeit with added costs. The DTW test most clearly segregates resistant and susceptible plants, thereby facilitating gene discovery and marker-assisted selection. We recommend that bulk testing be improved by switching from the SSST to a suitable MSST and that donor variety and pre-release lines be assessed for the nature of rice–planthopper interactions using biomass build-up tests—including the DTW test.

Irrigated rice croplands are among the most biologically diverse agroecosystems globally; however, intensification and simplification of farmed areas into homogeneous monocultures can lead to biodiversity loss and a reduction of associated ecosystem services such as natural pest regulation. Understanding how landscape heterogeneity affects the diversity of arthropod communities is therefore crucial for the sustainable management of rice agroecosystems. Here, we examine the influence of fine-scale landscape heterogeneity and regional-scale effects on the arthropod communities of three rice-production regions in the Philippines. Our analysis of 213 arthropod morphospecies (37,339 individuals) collected using two sampling methods at 28 field sites indicated that the rice agroecosystems in each study region had unique arthropod assemblages, likely reflecting region-specific environmental and land-use conditions. For all sites together, we found no effect of fine-scale landscape context (classified as rather high or low heterogeneity sites) on assemblage structure (arthropod abundance, species richness or diversity). When assemblages were analyzed separately, significant effects of fine-scale landscape context were only detected in one region and for two functional groups (predators and detritivores). Elevation gradient, used as a proxy for regional-scale effects in the study regions, explained more than 60% of variance in assemblage structure. Total arthropod abundance and rarefied species richness were negatively related to elevation, suggesting that regional-scale effects rather than fine-scale landscape heterogeneity explained the composition of rice-arthropod communities in landscapes. To further disentangle the complex effects of broad-scale environmental drivers versus fine-scale landscape complexity on arthropod communities and biocontrol services, future research in rice agroecosystems should focus on a more detailed quantification of landscape heterogeneity and examine its effect at multiple spatial scales.

Ecological engineering using vegetable or flower strips is promoted as a potential pest management strategy in irrigated rice. Farmers in the Philippines often plant rice levees (bunds) with vegetables, particularly string beans (Vigna unguiculata [L.] Walpers) to supplement income, but without considering the potential for pest management. This study examines the effects of planted bunds on rice herbivores and their natural enemies. We compared arthropods in (a) rice fields that had string beans planted on bunds, (b) fields without string beans and without any insecticide applications and (c) fields without string beans but with insecticide treatments (standard practice). Rice yield was similar across all treatments; however, the vegetation strips produced an extra 3.6 kg of fresh string bean pods per metre of bund. There were no apparent increases in major natural enemy groups in fields with string beans compared to fields with conventional bunds. Fields with insecticide treatments had higher damage from leaffolders (Lepidoptera: Pyralidae). The sprayed fields also had lower parasitism of planthopper eggs and fewer predatory dragonflies and damselflies (Odonata). Furthermore, the mortality of planthopper (Delphacidae: Hemiptera) and stemborer (Pyralidae) eggs by parasitoids and predators was density dependent only in the unsprayed fields (with and without string beans). Our results demonstrate that planting string beans on rice bunds improves the productivity of rice farms, but our ecological engineering system did not appreciably affect natural enemy or herbivore abundance; however, chemical insecticides adversely affected pest regulatory ecosystem functions leading to higher pest damage.

© 2016 Ecological Society of Australia Microbats perform important ecological services in agro-ecosystems, but several species are globally threatened by loss of roosting and breeding habitats. The successful conservation of bats in agricultural land requires adequate knowledge of their ecology. Using ultrasonic recorders, we studied the activity of insectivorous bats in areas of macadamia production in eastern Australia at two spatial scales: across woodland-orchard transects at the local scale and across three levels of fragmentation at the landscape scale. At the local scale, activity patterns of ‘clutter’ and ‘edge’ specialists were consistently higher in woodland patches, gradually decreasing towards isolated orchards, where only a few ‘open’ specialists were active. At the landscape scale, bat community activity was affected by the level of fragmentation, partly because three of the most recorded taxa (Austronomus australis, Saccolaimus flaviventris and Miniopterus australis) had their highest activity in less-fragmented areas. A distance-based model explained 24% of the bat community activity based on a combination of six environmental variables. Canonical correspondence analysis showed that a number of bat taxa were associated with open areas of macadamia, whereas other taxa were associated with increasing values of landscape composition, and arthropod and water availability. In addition, total bat activity was highly correlated with foraging rate. These results suggest that most bat taxa were influenced by proximity to woodland and the degree of fragmentation, and only few taxa were able to exploit isolated orchards. Environmental factors that promote bat activity could be exploited to strengthen conservation efforts. Preserving remnant woodland and promoting habitat heterogeneity will benefit several bat species. In particular, the foraging activity of ‘edge’ specialists could be fostered by increasing landscape connectivity and maintaining unobstructed water bodies near macadamia orchards. Considering that bats forage as they navigate these areas, conservation efforts could also bring benefits to farmers through pest-reduction services.

The brown planthopper (BPH: Nilaparvata lugens St&aring, l.) is a major pest of rice, Oryza sativa, in Asia. Host plant resistance has tremendous potential to reduce the damage caused to rice by the planthopper. However, the effectiveness of resistance genes varies spatially and temporally according to BPH virulence. Understanding patterns in BPH virulence against resistance genes is necessary to efficiently and sustainably deploy resistant rice varieties. To survey BPH virulence patterns, seven near-isogenic lines (NILs), each with a single BPH resistance gene (BPH2-NIL, BPH3-NIL, BPH17-NIL, BPH20-NIL, BPH21-NIL, BPH32-NIL and BPH17-ptb-NIL) and fifteen pyramided lines (PYLs) carrying multiple resistance genes were developed with the genetic background of the japonica rice variety, Taichung 65 (T65), and assessed for resistance levels against two BPH populations (Hadano-66 and Koshi-2013 collected in Japan in 1966 and 2013, respectively). Many of the NILs and PYLs were resistant against the Hadano-66 population but were less effective against the Koshi-2013 population. Among PYLs, BPH20+BPH32-PYL and BPH2+BPH3+BPH17-PYL granted relatively high BPH resistance against Koshi-2013. The NILs and PYLs developed in this research will be useful to monitor BPH virulence prior to deploying resistant rice varieties and improve rice&rsquo, s resistance to BPH in the context of regionally increasing levels of virulence.

Integrated biodiversity management aims to conserve the beneficial species components of production ecosystems and reduce the impacts of pests. In 2011 and 2013, experiments were conducted at Los Ba&ntilde, os, Laguna, Philippines, to compare arthropod communities in rice plots and on levees with and without vegetation strips. Vegetation strips included spontaneous weeds, sesame and okra (2011), or mung bean (2013). The plots were treated with one of three nitrogen levels and in one experiment were planted with planthopper-resistant (IR62) and susceptible (IR64) rice varieties. Parasitoids and predators of lepidopteran pests and of the ricebug, Leptocorisa oratorius, were more abundant in high-nitrogen rice plots where their prey/hosts also had highest densities. Planthoppers and leafhoppers were more abundant in low-nitrogen plots. Weedy and sesame/okra bunds provided habitat for a range of natural enemies including spiders, parasitoids and predatory bugs, but did not have higher pest numbers than cleared bunds. Higher abundances of the predator Cythorhinus lividipennis and higher parasitism of planthopper (Nilaparvata lugens) eggs by Anagrus sp. were associated with sesame/okra bunds in late season rice plots. Mung bean also provided habitat for key predators and parasitoids that spilled over to adjacent rice, however, mung bean was also associated with higher numbers of lepidopteran and grain-sucking pests in the adjacent rice, albeit without increased damage to the rice. For ricebug in particular, damage was probably reduced by higher parasitoid:pest ratios adjacent to the vegetation strips. Varietal resistance and mung bean strips had an additive effect in reducing abundance of the planthopper Sogatella furcifera and the leafhopper Nephotettix virescens. Reduced numbers of these latter pests close to vegetation strips were often compensated for by other plant-sucking bugs, thereby increasing the intensity of potentially stabilizing interspecific interactions such as competition. We highlight the benefits of diversifying rice landscapes and the need to optimize vegetation strips, e.g., by including lepidopteran trap-plants, for intensive rice production systems.

High-flying insectivorous bats, as wide-ranging generalist insectivores, are valuable consumers of high-altitude migrating pests of rice in Southeast Asia. Here, we documented the behavior of relatively low-flying bats over irrigated rice to elucidate their potential role as predators of rice-associated pest insects in the Philippines. Specifically, we tested the local-scale effects of rice stage, particularly seedling and late vegetative stages, and time of night on acoustic activity of bats foraging near ground level within three functional guilds (based on foraging distance from background clutter). We also monitored bat activity from two 50 m-high towers to assess the vertical extent of relatively low-flying guilds, as well as document high-flying bat guild presence and temporal behavior. At ground level, the most active guild biased their activity and feeding over early growth stage fields, but also foraged at tower level. Activity of the bat guild adept at foraging closest to vegetation did not vary with time of night or rice stage and was absent from tower recordings. High-flying bats were predictably rare at rice level, but exhibited high foraging intensity at 50 m. Given the well-documented, sequential arrival of insect guilds with growth stage, these data suggest that at ground level edge-space bats may be important consumers of detritivores (e.g., mosquitoes). Moreover, our data suggest that just as habitat heterogeneity enhances the services of arthropod predators, these management practices also enhance bat activity and, presumably, their contribution to pest suppression.

Yield losses from rice stem borers depend on the nature of the rice variety, the timing of attack, and the composition of the stem borer species assemblage. This study uses a range of phenotyping methods to distinguish different categories of herbivore-rice interaction that determine relative damage levels (dead heart and whitehead-panicles) and yield losses to varieties exposed to stem borers. Phenotyping studies were conducted in a greenhouse, screen house and field using two stem borer species (Scirpophaga incertulas [yellow stem borer - YSB] and Chilo suppressalis [striped stem borer - SSB]) and 12 rice lines. Only YSB displayed oviposition preferences across rice varieties. Both stem borer species performed better (greater survival, shorter development times, heavier pupae) on rice at vegetative compared to reproductive growth stages, and SSB was less capable than YSB of developing on rice at reproductive growth stages. Stem borer larval survival, body weight, development time, and tiller damage across different rice varieties in greenhouse experiments was poorly correlated between the two stem borer species and for each of the species on rice at two different plant growth stages (vegetative and reproductive). In contrast, rice tillering and yield responses to the two stem borer species were often highly correlated, but only when plants were attacked at the reproductive stage. Short-term, controlled experiments revealed aspects of host resistance and relative changes in plant biomass and yield in response to damage (condition change). However, the results from controlled environments and field-plots were not generally correlated because plant vulnerability, i.e., relative exposure to stem borer attack due to crop duration, largely determined field damage. We recommend that phenotyping studies should differentiate between the resistance, tolerance and vulnerability of rice lines to complexes of stem borers in a given region. Single stem borer species experiments under controlled environments are useful to gain knowledge of the nature of rice-stem borer interactions; however, field testing with comparative treatments, particularly under high soil fertilizer levels that increase plant attractiveness, are better for assessing the relative propensities of rice varieties to incur damage and yield losses due to complexes of stem borers., Graphical abstract Image 1, Highlights • Stem borer-rice interactions are categorized as relative resistance, and tolerance. • Phenotyping with 2 stem borers on 12 rice lines was used to predict field damage. • Results from tests under controlled conditions poorly correlated with field results. • Vulnerability, determined by crop duration, had a large impact on field damage. • Field tests that distinguish resistance, tolerance and vulnerability are recommended.

This study examines the potential for ecological engineering to enhance the beneficial ecosystem services provided by birds in tropical rice fields. Bird activities were monitored at six sites in the Philippines with high-diversity vegetation patches (HDVPs) established as an ecological engineering approach to restore ecosystem services. Adjacent plots of conventional rice were monitored as controls. Predatory birds (shrikes, Lanius spp., grassbirds, Megalurus palustris, and kingfishers, Halcyon spp.) were more active in the ecological engineering fields where they foraged for arthropods and snails among the rice plants. Pied trillers, Lalage nigra, and yellow vented bulbuls, Pycnonotus goiavier, foraged more in the HDVPs than in rice. These birds mainly responded to the availability of bamboo for perching in the HDVPs, although patch vegetation beneath the bamboo was also used for perching by some species. Aerial hunters such as swallows, Hirundo spp., avoided HDVPs likely because the tall vegetation and bamboo stakes represented an obstacle for their flight. Small changes in the design of HDVPs could avoid any negative effects on foraging by swallows and swifts. The results indicate that ecological engineering of rice paddies can have multiple benefits for farmers and the environment, including improved nutrition for farming communities, the creation of habitat for wildlife, and the enhancement of regulatory ecosystem services provided by insectivorous and snail-eating birds.

Hybrid rice has been noted for its susceptibility to insects and diseases compared to pure-line (conventional) rice varieties. We investigated herbivory by Nilaparvata lugens, Sogatella furcifera and Scirpophaga incertulas on replicated three-line hybrid sets (parental and hybrid lines) in field and greenhouse experiments. In a field experiment, caterpillar densities and stemborer damage was similar among hybrid and parental lines. In field and greenhouse experiments, the cytoplasmic male sterile (CMS)-lines and maintainer lines had higher densities of planthoppers (including N. lugens and S. furcifera) than restorer or hybrid lines likely because of their wild abortive CMS-lineage. High nitrogen levels increased plant mortality due to N. lugens, but often reduced mortality from S. furcifera and S. incertulas: this was similar between hybrid and pure-line varieties. The hybrids were generally more tolerant of herbivory (lower biomass reductions per unit weight of insect) than the inbred parental lines. The addition of nitrogen to both the hybrid and pure-line varieties had contrasting effects on tolerance depending on the nature of the attacking insect: fertiliser increased tolerance to S. furcifera (lower losses of yield and shoot biomass per mg insect) and S. incertulas (lower yield, shoot and root biomass loss) but fertiliser reduced tolerance to N. lugens (higher loss of root biomass and no effects on yield and shoot biomass loss). Our results indicate that hybrid rice is not physiologically more susceptible to herbivores than are pure-line varieties even under high nitrogen conditions, but does have higher tolerance to insect damage.

This study examines the nature of intraspecific interactions among Nilaparvata lugens (Stal) (Hemiptera: Delphacidae) planthoppers feeding on resistant and susceptible rice varieties. Planthopper nymphs produced less honeydew and gained less weight when feeding on rice variety IR62 (resistant) compared to susceptible rice varieties. A series of bioassays was conducted that varied N. lugens nymph densities on IR62 and IR22 (susceptible). Increasing nymph density facilitated feeding by conspecifics; however, intraspecific competition increased mortality of nymphs on IR62 (but rarely on IR22). Furthermore, nymph weights declined with increasing conspecific density on IR22, and the effects were weak on IR62. More female nymphs than males survived on IR62 but this was not affected by density. Nitrogenous fertilizer increased competition among N. lugens on young plants of IR22, but not on IR62. Results indicate that nymphs have a low efficiency in accessing resources when feeding on IR62, even where the plants have received fertilizer. Female-biased survival and biomass compensation for mortality may promote population recovery after development on the resistant plant and accelerate adaptation to the resistant variety.

This study examines the utility of resistant varieties and their associated resistance genes against brown planthopper, Nilaparvata lugens (Stal), populations from South and South East Asia. A collection of 39 rice accessions that included resistant, tolerant and susceptible varieties and breeding lines were examined for performance against populations of N. lugens from India (4), Bangladesh (1), Myanmar (1), Vietnam (1), Indonesia (1), China (1), Taiwan (1), and the Philippines (2). Planthopper virulence varied between regions; however only 6 varieties were generally less damaged than the susceptible check Taichung Native 1 (TN1) among ≥50% of the test populations. Each of these 6 varieties contained multiple resistance genes. One further variety, also with multiple resistance genes, and a modern cultivar (possibly with the Bph3 gene) were moderately effective against the South Asian populations, whereas a traditional variety with the Bph6 gene was effective against South East Asian populations. Bph1 , bph2 , bph5 , bph7 , bph8 , Bph9 , Bph10 and Bph18 were ineffective against most planthopper populations. Bph20 , Bph21 , and Bph17 have potential to be used in resistance breeding in both South and South East Asia, whereas BPH25 and BPH26 have potential for use in South Asia. The results indicate that only a few of the currently available resistance genes will be effective in monogenic rice lines; but that pyramiding of two or more genes with strong to weak resistance could improve resistance strength and durability as apparent with the most resistant, traditional varieties. Strategies to avoid planthopper adaptation to resistant rice varieties are discussed.

The direct effects of rising global temperatures on insect herbivores could increase damage to cereal crops. However, the indirect effects of interactions between herbivores and their biotic environment at the same temperatures will potentially counter such direct effects. This study examines the potential for intraspecific competition to dampen the effects of optimal temperatures on fitness (survival × reproduction) of the brown planthopper, Nilaparvata lugens [BPH] and whitebacked planthopper, Sogatella furcifera [WBPH], two phloem-feeders that attack rice in Asia. We conducted a series of experiments with increasing densities of ovipositing females and developing nymphs on tropical and temperate rice varieties at 25, 30 and 35°C. Damage from planthoppers to the tropical variety was greater at 30°C compared to 25°C, despite faster plant growth rates at 30°C. Damage to the temperate variety from WBPH nymphs was greatest at 25°C. BPH nymphs gained greater biomass at 25°C than at 30°C despite faster development at the higher temperature (temperature-size rule); however, the effect was apparent only at high nymph densities. WBPH survival, development rates and nymph weights all declined at ≥ 30°C. At about the optimal temperature for WBPH (25°C), intraspecific crowding reduced nymph weights. Temperature has little effect on oviposition responses to density, and intraspecific competition between females only weakly counters the effects of optimal temperatures on oviposition in both BPH and WBPH. Meanwhile, the deleterious effects of nymph crowding will counter the direct effects of optimal temperatures on voltinism in BPH and on body size in both BPH and WBPH. The negative effects of crowding on BPH nymphs may be decoupled from resource use at higher temperatures.

Damage to grasses and cereals by phloem-feeding herbivores is manifest as nutrient and chlorophyll loss, desiccation, and a gradual decline in host vigour. Chlorophyll loss in particular leads to a succession of colour changes before eventual host death. Depending on the attacking herbivore species, colour changes can be difficult to detect with the human eye. This study used digital images to examine colour changes of rice seedlings during feeding by the brown planthopper, Nilaparvata lugens (Stål) and whitebacked planthopper, Sogatella furcifera (Horváth). Values for red (580 nm), green (540 nm) and blue (550 nm) reflectance for 39 rice varieties during seedling seed-box tests were derived from images captured with a digital camera. Red and blue reflectance gradually increased as herbivore damage progressed until final plant death. Red reflectance was greater from plants attacked by the brown planthopper than plants attacked by the whitebacked planthopper, which had proportionately more green and blue reflectance, indicating distinct impacts by the two planthoppers on their hosts. Analysis of digital images was used to discriminate variety responses to the two planthoppers. Ordination methods based on red-green-blue reflectance and vegetation indices such as the Green Leaf Index (GLI) that included blue reflectance were more successful than two-colour indices or indices based on hue, saturation and brightness in discriminating between damage responses among varieties. We make recommendations to advance seed-box screening methods for cereal resistance to phloem feeders and demonstrate how images from digital cameras can be used to improve the quality of data captured during high-throughput phenotyping.

Efforts to increase food production across Asia have relied on the intensification of established farms, as well as the expansion of farming activities into previously wild areas. Farms at agricultural frontiers face distinct challenges from those in historically farmed regions and require distinct support structures. We interviewed 324 rice farmers at seven sites in southern Sri Lanka to determine challenges to rice production in the region and the propensity for human wildlife conflict. Farmers (80%) reported wildlife including peafowl (Pavo cristatus) and other birds, as well as free-ranging (semi-)domestic animals such as buffalo (Bubalus bubalis), as their principal biotic constraints across sites, with relatively few farmers regarding weeds, insect pests, or diseases as a constraint (mentioned by 25% of farmers in total). Farmers near wilderness areas reported elephants (Elephas maximus) and wild boar (Sus scrofa) as major constraints to rice production. 64% of farmers had received training from government and other support agencies during the five years prior to our survey. Training mainly addressed insect pests and diseases and focused on lethal product-based solutions (88% of training). Farmers did not receive support or advice to mitigate crop foraging and human-wildlife conflict; instead, farmers relied heavily on repellence (human activated) responses, such as early warning systems and active scaring. We suggest that Agriculture, Development and Wildlife authorities might increase intergovernmental cooperation and coordination of farmer training to better manage crop foraging in our study region. We present a review of possible non-lethal, farm-based methods that could be promoted during training programs for farmers facing challenges from wildlife in such a biologically diverse region. Currently, a wide range of low-cost avoidance, barrier and deterrence systems (that are not monitored or activated by humans) are available. These can be used to avoid harmful repellence practices.

© 2017 E. The effects of nitrogenous fertilizers on black bug (Hemiptera: Pentatomidae) colonization and population development in rice fields has not been studied previously. This study reports on the distribution of adults, eggs and nymphs of the black bug, Scotinophara latiuscula (Breddin) during a seasonal outbreak in a rice (Oryza sativa L.) yield experiment that varied nitrogen application rates. Plots at the edge of the experimental field had higher black bug densities. Adult distribution was only weakly affected by nitrogen level. Densities of egg-masses and nymphs increased linearly with increasing nitrogen rates. Nymph development was also more advanced under high nitrogen. Oviposition was highest on larger plants with high grain numbers (actively filling grain), but was otherwise unaffected by the varieties in the experiment. Our results indicate that the build-up of black bug populations in rice is influenced by nitrogen fertilizer rates mainly acting on egg-laying and nymph development.

The planthoppers Nilaparvata lugens (Stal) and Sogatella furcifera (Horvath) co-occur on rice Oryza sativa L., throughout much of Asia. Nilaparvata lugens is regarded as the more destructive rice pest. Interactions between these two species on individual rice plants can be positive (interspecific facilitation) or negative (interspecific competition). However, the outcome of their interactions on resistant rice varieties has received little attention despite the potential consequences for adaptation to resistance. In this study, we examine interactions between nymphs of these two species on resistant (IR62 and ADR52) and susceptible (IR22) rice varieties. IR62 was resistant to N. lugens at all plant ages, but only older plants were resistant to S. furcifera. ADR52 was resistant to S. furcifera, and gained moderate resistance to N. lugens as the plants aged. Nilaparvata lugens facilitated weight gain in S. furcifera even on the resistant IR62 variety. However, facilitation by N. lugens was reduced on older ADR52 plants when resistance against S. furcifera was strongest. Sogatella furcifera reduced weight gain in N. lugens on susceptible varieties, but failed to out-compete N. lugens where plants expressed S. furcifera-resistance. Our preliminary results indicate that competition from S. furcifera could slow adaptation by N. lugens to resistant rice varieties. Facilitation by N. lugens of S. furcifera on resistant rice, which is expected to increase adaptation rates in the latter species, likely depends on the relative strengths of resistance against both planthoppers.

This study examines the resistance of recently developed near-isogenic rice lines (NILs) with BPH25 and BPH26 genes and the resistance donor cultivar ADR52 against Philippine populations of the brown planthopper, Nilaparvata lugens (Stal). Monogenic and pyramided lines with BPH25 and BPH26 were largely ineffective against the planthopper in a series of laboratory bioassays. In previous studies, BPH25 and a pyramided BPH25 + 26-NIL had been effective in reducing the fitness of N. lugens collected in Mindanao (Philippines); however, the virulence of the planthopper appears to have developed recently in Mindanao so the NILs are now ineffective. ADR52 showed marginal resistance against N. lugens, was more generally resistant against the white-backed planthopper, Sogatella furcifera (Horvath), and had strong resistance against the green leafhopper, Nephotettix virescens (Distant). Resistance against the latter two species was not derived from either BPH25 or BPH26, indicating that the cultivar possesses other resistance genes. For all three insect species, egg laying was constant on ADR52 as the plants aged; however, resistance against nymphs of all three insects increased as ADR52 aged. ADR52 had generally high tolerance against all three insects, which increased under high nitrogen conditions. The results of this study indicate ADR52 is a potential source of further resistance genes against leafhoppers and planthoppers. However, the results also indicate the need to carefully manage resistance genes to avoid adaptation by target insects as has occurred with BPH25 and BPH26.

© 2017 The Netherlands Entomological Society Insect herbivores form symbioses with a diversity of prokaryotic and eukaryotic microorganisms. A role for endosymbionts during host feeding on nutrient-poor diets – including phloem – is now supported by a large body of evidence. Furthermore, symbiont-herbivore associations have been implicated in feeding preferences by host races (mainly aphids) on multiple plant species. However, the role of symbionts in mediating herbivore preferences between varieties of the same plant species has received little research attention despite the implications for virulence adaptation to resistant crops. This study investigates the role of yeast-like symbionts (YLS) in virulence adaptation and host plant switching among populations of the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), that were selected on various rice [Oryza sativa L. (Poaceae)] lines differing in their resistance against herbivores. Planthopper fitness (nymph weight) declined where YLS densities were depleted through heat treatment. However, compared to normal symbiotic planthoppers, the depletion of symbionts did not generally change the relative fitness of planthoppers (each ‘adapted’ to a single natal host) when switched to feed on a range of rice lines (exposed hosts). In some cases, this occurred despite differences in YLS density responses to the various hosts. Furthermore, we detected no fitness costs associated with YLS in adapted populations. Therefore, the results of this study suggest that, whereas YLS are essential for planthopper nutrition, changes in YLS density play little role during virulence adaptation and host plant switching by the brown planthopper.

Apple snails (Ampulariidae) occur throughout tropical and subtropical rice-growing regions. Native apple snails rarely damage rice; however, in hot and humid tropical regions, some native species will damage wet-direct-seeded rice (i.e., Pomacea spp. in Suriname and Brazil). Similarly, exotic apple snails in wet, temperate regions can damage direct-seeded rice (i.e., Pomacea canaliculata in Japan). However, if left unmanaged, exotic apple snails in warm tropical regions (i.e., P. canaliculata and P. maculata in South East Asia) can cause significant economic losses even to transplanted rice (which is more robust that direct-seeded rice). The negative impact of apple snails on rice yield can be reduced by reducing seedling vulnerability or controlling snail population densities. Reducing vulnerability is a more sustainable solution to apple snails but requires new methods such as seedling broadcasting and machine transplanting to decrease labor costs. To avoid further spread of apple snails, the implementation of effective quarantine directives is recommended for tropical countries that are vulnerable to exotic apple snails.

2017 by the authors. This study examines aspects of virulence to resistant rice varieties among planthoppers and leafhoppers. Using a series of resistant varieties, brown planthopper, Nilaparvata lugens, virulence was assessed in seedlings and early-tillering plants at seven research centers in South and East Asia. Virulence of the whitebacked planthopper, Sogatella furcifera, in Taiwan and the Philippines was also assessed. Phylogenetic analysis of the varieties using single-nucleotide polymorphisms (SNPs) indicated a clade of highly resistant varieties from South Asia with two further South Asian clades of moderate resistance. Greenhouse bioassays indicated that planthoppers can develop virulence against multiple resistance genes including genes introgressed from wild rice species. Nilaparvata lugens populations from Punjab (India) and the Mekong Delta (Vietnam) were highly virulent to a range of key resistance donors irrespective of variety origin. Sogatella furcifera populations were less virulent to donors than N. lugens; however, several genes for resistance to S. furcifera are now ineffective in East Asia. A clade of International Rice Research Institute (IRRI)-bred varieties and breeding lines, without identified leafhopper-resistance genes, were highly resistant to the green leafhopper, Nephotettix virescens. Routine phenotyping during breeding programs likely maintains high levels of quantitative resistance to leafhoppers. We discuss these results in the light of breeding and deploying resistant rice in Asia.

The management of insect herbivores in rice ecosystems has been strongly influenced by three poorly informed beliefs. These are (1) that insects have generally negative effects on crop health, (2) that herbivore damage translates directly to yield loss, and (3) that insecticides increase rice yields. In the face of global changes, particularly increases in the production and marketing of agrochemicals, these beliefs will lead to unsustainable rice production systems and poor environmental health. This chapter assesses these beliefs, challenges their validity, and (by analyzing the dynamics of herbivore populations and their interspecific interactions in the rice ecosystem) presents a holistic alternative for understanding herbivore impacts on rice production systems. The chapter proposes a focus on “rice ecosystem health” with herbivore management based on ecological principals and incorporating such novel approaches as “ecological engineering” for ecosystem stability and system resilience.

Since its introduction to Asia in the 1980s, the golden apple snail, Pomacea canaliculata (Lamarck), has represented a major constraint to the profitability of rice ( Oryza sativa L.) farming by damaging rice seedlings during crop establishment. This study describes a series of experiments designed to determine the effects of nitrogenous fertilisers on snail fitness. We examined the possibility of a two-phase model of snail response to nitrogen, whereby fertilisers initially increase snail mortality through toxicity, but once assimilated into the rice ecosystem, eventually favour snail reproduction and survival. In experimental arenas, fertiliser had lethal effects: Complete fertiliser (14:14:14), urea, ammonium sulphate and organic fertilisers were associated with snail mortality, generally affecting adult snails more than juvenile snails, and with greater effects when applied to saturated soil that was subsequently flooded (as opposed to direct application to flooded soil). Snail mortality was found to decline considerably when snails were added to arenas one day after fertiliser application - this occurred in arenas with soil and water, but not in arenas with water only, suggesting that soil can reduce the toxic effects of fertilisers. In a field experiment, snail numbers declined in both fertilised and non-fertilised plots at the time of crop establishment. Numbers increased in all plots after rice tillering, with significantly more recruitment in plots with high nitrogen. Although the responses were generally weak in the field experiment, they did support the two-phase model. The consequences of fertiliser applications for snail management and ecosystem health are discussed. © 2014 Elsevier Ltd.

At least 14 species of apple snail (Ampullariidae) have been released to water bodies outside their native ranges; however, less than half of these species have become widespread or caused appreciable impacts. We review evidence for the impact of apple snails on natural and managed wetlands focusing on those studies that have elucidated impact mechanisms. Significant changes in wetland ecosystems have been noted in regions where the snails are established: Two species in particular (Pomacea canaliculata and Pomacea maculata) have become major pests of aquatic crops, including rice, and caused enormous increases in molluscicide use. Invasive apple snails have also altered macrophyte community structure innatural and managed wetlands through selective herbivory and certain apple snail species can potentially shift the balance of freshwater ecosystems from clear water (macrophyte dominated) to turbid (plankton dominated) states by depleting densities of native aquatic plants. Furthermore, the introductions of some apple snail species have altered benthic community structure either directly, through predation, or indirectly, through exploitation competition or as a result of management actions. To date much of the evidence for these impacts has been based on correlations, with few manipulative field or mesocosm experiments. Greater attention to impact monitoring is required, and, for Asia in particular, a landscape approach to impact management that includes both natural and managed-rice wetlands is recommended. © 2012 Elsevier Masson SAS.

The green leafhopper, Nephotettix virescens (Distant) (Hemiptera: Cicadellidae), occasionally damages rice in Asia either directly, by feeding on the host phloem, or indirectly by transmitting tungro virus. We assessed the nature of resistance against the leafhopper in monogenic and pyramided near-isogenic rice lines containing the resistance genes Grh2 and Grh4. Only the pyramided line was resistant to leafhopper damage. Leafhopper nymphs and adults had high mortality and low weight gain when feeding on the pyramided line and adults laid few eggs. In contrast, although there was some minor resistance in 45-day-old plants that possessed either Grh2 or Grh4 genes, the monogenic lines were generally as susceptible to the leafhopper as the recurrent parent line Taichung65 (T65). Resistance in the pyramided line was stable as the plant aged and under high nitrogen, and affected each of five Philippine leafhopper populations equally. Furthermore, in a selection study, leafhoppers failed to adapt fully to the pyramided resistant line: nymph and adult survival did improve during the first five generations of selection and attained similar levels as on T65, but egg-laying failed to improve over 10 generations. Our preliminary results suggested that resistance was associated with physiological costs to the plants in some experiments. The results of this study demonstrate the success of pyramiding resistance genes through marker-assisted breeding, to achieve a strong and potentially durable resistance. We discuss the utility of gene pyramiding and the development of near-isogenic lines for leafhopper management.

A global decline in pollinator abundance and diversity has demanded increased research attention to the ecology and genetics of bumblebees. However, as progressively more restrictions are placed on sampling for insects, researchers are increasingly obliged to use archival specimens collected for purposes other than genetic analyses. In this study we assessed the suitability, for population genetic studies, of popular, low-cost methods for preservation and storage of bumblebee specimens. Specimens of Bombus terrestris L. were held under six storage regimes for up to two years. DNA was extracted from the samples using three extraction protocols and the quality of the DNA was examined using PCR amplification of a mitochondrial and a nuclear gene. All extraction and storage methods provided sufficient DNA for successful PCR amplification. However, samples preserved in acetone or at freezing temperatures yielded the highest DNA concentrations. DNA yields from pinned specimens at room temperature declined over time, particularly when using standard extraction techniques. DNA concentrations were significantly lower from speci- mens preserved in 70% ethanol compared to all other extraction techniques and declined linearly over the two years of storage. These results indicate that two of the most popular insect storage methods (pinning and storage in ethanol) should be avoided for the long-term preservation of genetic material for future studies. We suggest that optimal insect preservation methods should be incorpo- rated into research protocols in order to best capitalise on limited collection opportunities.

Since the late 1970s, the area of agricultural land dedicated to hybrid rice has rapidly increased throughout Asia, particularly in China, India, and Vietnam. The pace of hybrid adoption, a generally low genetic diversity of hybrid varieties, and higher agrochemical inputs with hybrid rice compared to conventional varieties has significantly changed the rice landscape. Some authors have associated these changes with an increasing incidence of damage to rice by herbivorous insects. This review examines trends in hybrid adoption in Asia, the associated problems with insect herbivores, and possible solutions to these problems. A series of hypotheses are presented to explain the increased incidence of damage as related to issues of crop susceptibility (hybrid physiology and genetics) and crop vulnerability (management-related issues). Evidence suggests that hybrid rice has been highly vulnerable to damage from a range of insects. Inadequate attention to issues of planthopper resistance, linked with high agrochemical inputs and a new, vigorous rice type, likely contributed to high levels of planthopper damage in some hybrid rice varieties. Furthermore, hybrid susceptibility to the whitebacked planthopper, Sogatella furcifera (Horvath) (Hemiptera: Delphacidae), has been linked to the female (wild abortive-cytoplasmic male sterile) parent of some hybrid lines. Meanwhile, a high incidence of stem borer damage to hybrids has likely resulted from the interaction of several plant traits with normal hybrid management, and particularly with the higher fertilizer applications associated with hybrid rice. Despite apparently low levels of resistance, hybrid varieties have high tolerance to herbivore damage; however, aspects of hybrid tolerance have been largely neglected in the literature, in breeding programs, and during development of pest management actions. This review suggests that research into the entomology of hybrid rice needs updating as hybrid varieties and management options continue to change over time. Pest management areas that require further research (including strategies for deployment of resistant varieties) are highlighted and a call is made for increased attention to issues of hybrid tolerance for sustainable herbivore management.

The diversification of resistant potato varieties at a landscape level couldslow adaptation by Phthorimaea operculella to potato resistance and pro-mote sustainable crop protection. In this study, we assessed wild potatospecies as novel sources of foliage and tuber resistance against P. operculel-la. Tuber resistance was quantified for 136 and foliage resistance for 54potato accessions representing 14 and nine potato species, respectively.Several accessions were highly resistant to moth damage in tubers and/orfoliage. In particular, Solanum chiquidenum and Solanum sandemanii werehighly resistant to damage in tubers. Several accessions of Solanum multiin-terruptum and a small number of accessions of Solanum bukasovii, Solanumberthaultii, Solanum sparsipilum and Solanum wittmackii also had highlyresistant tubers. Larval survival on foliage of S. bukasovii and S. chiquide-num was generally low. New resistance sources are listed, and insect per-formance on the plants is described with possible resistance mechanisms.The study also examined potential trade-offs associated with resistance.Tuber resistance was negatively correlated with the number and weight oftubers produced per plant, but positively correlated with the length of dor-mancy across accessions, indicating that, although long dormancy is not aprerequisite for resistance, species and accessions with extended dor-mancy will have more resistant tubers. Tuber and foliage resistance weregenerally positively correlated across all accessions; however, amongaccessions from within a potato species, there were negative (S. berthaul-tii), positive (S. chiquidenum) and non-significant (S. bukasovii) relations.These results indicate that, besides identifying novel resistance sources, animproved understanding of the mechanisms and inherent trade-offs asso-ciated with tuber and foliage resistance will improve the efficiency ofpotato breeding programmes aimed at enhancing resistance againstP. operculella.IntroductionThe potato tuber moth, Phthorimaea operculella(Zeller), is one of the most damaging insect pests ofcrop potato (Solanum tuberosum Grp Tuberosum)worldwide (Rondon 2010; Pelletier et al. 2013). Thetuber moth causes serious losses to potato productionby damaging foliage and tubers in the field and tubersin storage (Rondon 2010). Moth infestations of tubersin rustic storage facilities, particularly in tropical andsubtropical regions, can sometimes cause the com-plete loss of farmers’ potato stocks. Even when mothdamage is not severe, bacteria and fungi will some-times infect potato tubers through wounds created bythe moths, causing a reduction or loss of market value(Rondon 2010). Commercial and edible native pota

Hybrid and pure-line (inbred) rice (Oryza sativa L. (Poaceae)) varieties have distinct physiologies, particularly as related to their nutrient requirements. These differences could confound the results and interpretation of experiments that compare rice varieties grown in pots for their resistance and responses to herbivores. In this study, a series of experiments was conducted to identify potentially confounding interactions between pot size (soil volume), fertilizer regime, and the use of acetate insect cages with rice line type (hybrid, fertile parental inbred, and male sterile inbred) during bioas- sayswiththebrownplanthopper,Nilaparvatalugens(Stal)(Hemiptera: Delphacidae). Thegrowthof hybrid rice was often limited (relatively low biomass and low grain production) compared to fertile inbred lines even in large pots (7 200 ml) and when grown without added fertilizer. Several interac- tions between theeffects ofgrowth conditions andline typewere detected. Acetatecages causeda sig- nificant reduction in grain yield in hybrids, but not in inbreds, mainly resulting from a cage-induced decrease in grain weight (smaller grains). Hybrids and male sterile lines often had higher root or above-ground biomass in the largest caged pots compared with fertile inbred lines, but biomass was similar in smaller pots, indicating that the large pots allowed longer unimpeded growth of fertile in- breds, but not other line types. There were no interactions between the presence or absence of plant- hoppers with line type or experimental conditions. All line types were equally susceptible to planthoppers. Often the effects ofplanthopper feeding on plantfitness (i.e., tolerance) were apparent when plants were grown in large pots but not in small pots, particularly for hybrid lines and under highnitrogenregimes.Onthebasisoftheseresultswerecommendthatresearchersensurethatplants are not unequally stressed by inadequate growth conditions during comparative studies with herbi- vores on physiologically distinct rice varieties or rice species. We recommend the use of large pots (soil volume) and lower fertilizer levels with young, non-reproductive plants during comparative bioassays with planthoppers. Field cages are recommended for hybrid-inbred comparisons during older plant stagesbut thesearesubjecttoa rangeofotherconfoundingvariables.

Highlights ► We determine the permeability of cropping systems to commercial bumble bees. ► We quantify the prevalence of pathogens in bumble bees adjacent to greenhouses. ► Up to 97% of pollen returning to commercial bumble bee hives was non-crop pollen. ► The prevalence of two gut parasites was greatest within 2 km of greenhouses. ► Pathogen spillover in this system compels national and international regulation., Worldwide, wild bumble bees (Bombus spp.) are experiencing marked declines, with potentially up to 11% of species currently under threat. Recent studies from North America suggest that disease transmission from commercially reared bumble bees to wild populations has led to marked range contractions in some species. In Europe, data on the prevalence of pathogen spillover from commercial to wild bumble bee populations is lacking, despite the widespread production and transport of hives within the EU since the early 1980s. We determined the permeability of cropping systems to commercial bumble bees, and quantified the prevalence of four pathogens in commercial Bombus terrestris hives and adjacent conspecific populations at increasing distances from greenhouses in Ireland. Commercial bumble bees collected from 31% to 97% of non-crop pollen, depending on the cropping system, and hives had markedly higher frequencies of two gut parasites, Crithidia spp. and Nosema bombi, compared to adjacent populations, but were free of tracheal mites. The highest prevalence of Crithida was observed within 2 km of greenhouses and the probability of infection declined in a host sex- and pathogen-specific manner up to 10 km. We suggest implementing measures that prevent the interaction of commercially reared and wild bumble bees by integrating the enforcement of national best management practices for users of commercial pollinators with international legislation that regulates the sanitation of commercial hives in production facilities.

For over 50 years, host-plant resistance has been regarded as an efficient method to reduce yield losses to rice caused by delphacid and cicadelid hoppers. Already a number of resistant rice varieties have been developed and deployed throughout Asia. To date, over 70 hopper resistance genes have been identified in rice; however, less than 10 genes have been deliberately introduced to commercial rice varieties. Currently, due to recent brown planthopper (Nilaparvata lugens [Stål]) and whitebacked planthopper (Sogatella furcifera [Horvath]) outbreaks occurring at an unprecedented scale, researchers are working toward a second generation of resistant varieties using newly identified gene loci and applying new molecular breeding methods. This paper reviews advances in the identification of resistance genes and QTLs against hoppers in rice. It collates all published information on resistance loci and QTLs against the major rice planthoppers and leafhoppers and presents information on gene locations, genetic markers, differential varieties, and wild rice species as sources of resistance. The review indicates that, whereas progress in the identification of genes has been rapid, considerable tidying of the information is required, especially regarding gene nomenclature and resistance spectra. Furthermore, sound information on gene functioning is almost completely lacking. However, hopper responses to resistance mechanisms are likely to be similar because a single phenotyping technique has been applied by most national and international breeding programs during germplasm screening. The review classifies genes occurring at two chromosome regions associated with several identified resistance loci and highlights these (Chr4S: BphR-R and Chr12L: BphR-R) as general stress response regions. The review calls for a greater diversity of phenotyping methods to enhance the durability of resistant varieties developed using marker-aided selection and emphasizes a need to anticipate the development of virulent hopper populations in response to the field deployment of genes. © 2013 Copyright Taylor and Francis Group, LLC.

Meloidogyne minor, first reported on potatoes in the Netherlands in 2004, is an emerging nematode pest in Europe. It damages turfgrass, particularly creeping bentgrass (Agrostis stolonifera) grown on sandy soils such as those of golf greens. However, little is known of the nematode's life history and pathology. In this study, the spatial and temporal distribution of M. minor on a creeping bentgrass green in Ireland was determined over a 15 month period. Cores were taken on transects across yellowing patches of grass caused by nematode damage. Second-stage juveniles (J2) were absent from the soil from November to February, when soil temperatures were below 10°C. Both galls and egg masses were present throughout the year but were more abundant in late summer and early autumn. More J2, galls and egg masses were present in the top 10 cm of soil than at a depth of 11-20 cm. The nematode population tended to decrease as distance from the centre of the yellow patches increased. The diameter of visual symptoms (yellow patches) was also recorded over the 15 months. The mean diameter of five sampled patches increased from 23·7 cm in June 2003 to 45·2 cm in August 2004. There were 158-193 galls per 100 cm3 soil at the margin of the visible infested area, indicating that this could be the threshold level for visible symptoms. © 2012 British Society for Plant Pathology.

This study examines the possibility of horizontal and vertical transmission of virulence (the ability to tolerate a given resistant plant or resistance gene) between individuals from brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), populations with distinct feeding abilities when their populations share the same feeding sites (virulence acquisition hypothesis). We created optimal conditions for intraspecific interactions on the same rice, Oryza sativa L. (Poaceae), plants between planthoppers from populations with different feeding histories: an ‘avirulent’ population that was continually reared on a susceptible variety, and a ‘virulent’ population that had been selected over several generations on the resistant variety IR62, that possesses the Bph3 gene. We noted that planthoppers attained highest weights on rice plants that had previously been attacked by conspecifics from the IR62-selected population. We also tested the ability of planthoppers to feed on IR62 and the susceptible cv. Taichung Native 1 (TN1) after interacting with individuals from the IR62-selected population on a tolerant rice cultivar (Triveni). Feeding by avirulent planthoppers on both IR62 and TN1 improved after feeding on the same rice plants with virulent planthoppers. Furthermore, the effects were carried over to planthopper progenies. Our preliminary results indicate that feeding by mixed populations that include individuals adapted to feed on resistant varieties potentially accelerates adaptation by N. lugens to rice resistance.

In the inter-Andean valleys of central Perú, two species of tuber moth, Phthorimaea operculella (Zeller) and Symmetrischema tangolias (Gyen), often occur simultaneously in stored potatoes. Traditional farming communities in the region produce a variety of native potatoes for local consumption. These include Solanum tuberosum subsp. andigena, the presumed predecessor of commercial potatoes, S. tuberosum subsp. tuberosum. In this study, we examined resistance against P. operculella in ten native Peruvian potato varieties (Casa blanca, Chispiadita, Madre de vaca, Mamaco negro, Misha, Chorisa, Mamaco rosado, Occa papa, Vacapa jayllo, and Yana tornasol). We also compared resistance in the first five of these varieties against S. tangolias. Varieties with pigmented periderms showed moderate resistance (30-40% against P. operculella in Mamaco negro, Mamaco rosado, and Yana tornasol and 55% against S. tangolias in Mamaco negro). All the other varieties were susceptible to both moth species. Small tubers tended to be the most resistant to the attack by both moths; however, this was not related to the availability of food for developing larvae, since pupal weight and development time were unaffected by the size of tubers. Similar responses by the two moths to native potatoes indicate that tuber resistance could be used to control the complex of tuber moths that damage potatoes in the Andes. We suggest that native potatoes, which are often easily introgressed with commercial potatoes, are a potential source of resistance against tuber moths.