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Lycorma delicatula (White) (Hemiptera: Fulgoridae), native to China, was first detected in Pennsylvania, U.S. in 2014. This polyphagous pest can feed on over 70 plant species including agricultural crops, like grapes, that have high economic value. Anastatus orientalis Yang and Choi (Hymenoptera: Eupelmidae) is an egg parasitoid associated with L. delicatula egg masses in China that is being evaluated for possible introduction into the U.S. for classical biological control of L. delicatula. In support of this program, the suitability of frozen L. delicatula eggs for parasitization by A. orientalis was evaluated in a quarantine laboratory. Host egg masses held for four different cold storage periods (5°C for A. orientalis for parasitization for seven days. Following this experimental exposure period, rates of L. delicatula nymph emergence and A. orientalis parasitism were assessed for each of the eight different cold storage treatments. Host acceptance and suitability of frozen L. delicatula eggs by A. orientalis was assessed in terms of percentage parasitism, offspring sex ratio, and hind tibia length of emerged parasitoids. Results indicated that L. delicatula nymphs failed to emerge from eggs that were exposed to -40°C for 1 hour and 24 hours and A. orientalis could successfully parasitize L. delicatula eggs regardless of cold storage and freezing treatment. These results add a new tool for long term maintenance of L. delicatula egg masses and rearing methods for egg parasitoids of this pest. Additionally, it may be possible to field deploy sentinel eggs of L. delicatula frozen at -40°C to survey for resident natural enemy species capable of parasitizing eggs of this pest in advance of anticipated L. delicatula invasions into new areas.

Funding: This work was supported by a number of fellowships, namely a University Research Fellowship from Royal Society of London (to AG) and a Junior Research Fellowship from Balliol College, Oxford to AG. Funding came from Independent Research Fellowships from Natural Environment Research Council (grant no. NE/K009524/1 to AG and NE/K009516/1 to LR), a Consolidator Grant from European Research Council (grant no. 771387 to AG), a European Research Countil Starting Grant (PGErepro to LR), and a Royal Society Newton fellowship (to LR). Androdioecy (the coexistence of males and hermaphrodites) is a rare mating system for which the evolutionary dynamics are poorly understood. Here we study the only presumed case of androdioecy in insects, found in the cottony cushion scale, Icerya purchasi . In this species, female-like hermaphrodites have been shown to produce sperm and self-fertilize. However, rare males are sometimes observed too. In a large population-genetic analysis, we show for the first time that although self-fertilization appears to be the primary mode of reproduction, rare outbreeding events between males and hermaphrodites do occur, and we thereby confirm androdioecy as the mating system of I. purchasi . Thus, this insect appears to have the colonization advantages of a selfing organism while also benefitting from periodic reintroduction of genetic variation through outbreeding with males. Publisher PDF

Heilipus lauri Boheman (Coleoptera: Curculionidae) is a specialist pest of avocado fruit and is considered an incursion risk for U.S. avocado producers. At the time work reported here was undertaken the flight capabilities of H. lauri were unknown. Consequently, proactive studies were undertaken to quantify aspects of this pest’s flight capabilities to inform potential future control efforts. Flight mill studies were conducted in a quarantine laboratory to measure the dispersal capacity of H. lauri with respect to gender, mating status, and size on the single and repeat flight capabilities of weevils. Gender, mating status, and size did not significantly affect measured flight parameters. Average total distances flown and flight velocity, and mean maximum flight bout distances and durations significantly declined as weevil age increased and when weevils engaged in repeat flights. Survivorship rates were significantly reduced as the number of successive flights undertaken increased. The distribution of total average flight distances flown and total cumulative flight distances flown was platykurtic. The implications of these findings are discussed in terms of developing incursion management plans.

The Argentine ant, Linepithema humile (Mayr), poses a significant economic threat to citrus production in southern California. Broad-spectrum insecticide sprays provide poor ant control and present a hazard to human and environmental health. Liquid sucrose bait infused with a low concentration of insecticide is an effective alternative treatment but current approaches require considerable economic investment in plastic dispensers and continual maintenance. To produce a baiting product for control of L. humile suitable for large-scale application, a biodegradable, broadcastable alginate hydrogel for delivery of aqueous low-dose thiamethoxam sucrose bait was developed and evaluated in replicated field trials in commercial citrus groves. Ant activity was significantly reduced in hydrogel-treated trees. Peak L. humile suppression was achieved 48 h following the final hydrogel disbursement, with an estimated 91% reduction in activity from baseline estimates and a 17-fold lower activity in treated trees in comparison with untreated trees. Significant residual activity of the hydrogel treatments was recorded, with a nearly 70% reduction from pre-treatment levels persisting at least 3 weeks after the last application. We conclude that alginate hydrogels can provide excellent control of L. humile while deploying 99.99% less insecticide into orchards than commercial barrier spray treatments.

The effects of six average daily temperatures, 15, 20, 25, 30, 32, and 35°C, that were either constant or fluctuating over 24 h on development times of California-sourced Diaphorina citri Kuwayama nymphs were examined. Thermal performance curves for immature stages of D. citri were characterized using one linear and six nonlinear models (i.e., Ratkowsky, Lobry-Rosso-Flandrois, Lactin-2, Brière-2, Beta, and Performance-2). Daily thermal fluctuations had significant effects on development times of D. citri nymphs, which differed across experimental temperatures. Diaphorina citri nymphs reared at constant temperatures completed development faster than those reared under fluctuating profiles with equivalent temperature means. Linear model estimates of degree-days required for completion of cumulative development of D. citri were 25% lower for constant temperatures when compared with fluctuating temperature regimens. Nonlinear model estimations of optimum developmental temperature and upper theoretical temperature bounds for development were similar for individuals reared under constant and fluctuating temperatures. Nevertheless, the estimated values of lower theoretical temperature limits above which development occurred were lower under fluctuating than constant temperatures. A meta-analysis of published D. citri temperature-dependent development literature, synthesizing datasets of five globally distributed populations (Brazil, California, China, Florida, and Japan) reared under different constant temperatures on six different host plants (i.e., Citrus limonia, C. sinensis cv Natal, C. sinensis cv. Pêra, C. reticulata, Fortunella margarita, and Murraya paniculata), together with the results of this study (C. volkameriana), revealed convergence in estimates of developmental parameters. These results have implications for predicting D. citri invasion and establishment risk and subsequent population performance across various climactic gradients and geographic regions.

The South American palm weevil, Rhynchophorus palmarum (Coleoptera: Curculionidae), established in San Diego County, California, USA sometime around 2014. Attached to the motile adults of this destructive palm pest, we identified three species of uropodine mites (Parasitiformes: Uropodina), Centrouropoda n. sp., Dinychus n. sp. and Fuscuropoda marginata. Two of these species, Centrouropoda n. sp. and Dinychus n. sp. are recorded for the first time in the USA and were likely introduced by R. palmarum. Several species of mites, primarily of Uropodina, have previously been recorded as phoretic on Rhynchophorus spp. In this study, we examined 3,035 adult R. palmarum trapped over a 2.5-year period, July 2016 to December 2018, and documented the presence of and species composition of phoretic mites and their relationship with weevil morphometrics (i.e., pronotum length and width). The presence and species composition of mites on weevil body parts changed over the survey period. No mites were found under weevil elytra in 2016 and mite prevalence under elytra increased over 2017–2018 due to an increased abundance of Centrouropoda n. sp per individual beetle. Mite occurrence levels were significantly correlated with reduced pronotum widths of male weevils only. The significance of this finding on male weevil fitness is unknown. Potential implications of phoretic mites on aspects of the invasion biology of R. palmarum are discussed.

Four palm species, previously unknown hosts for Rhynchophorus palmarum L. (Coleoptera: Curculionidae), were killed by this invasive palm weevil in Balboa Park, San Diego County, California, USA. The 4 new palm species recorded as reproductive hosts for R. palmarum for the first time are Brahea edulis, Jubaea chilensis, Phoenix reclinata, and Sabal bermudana (all Arecaceae). Phoenix canariensis Chabaud (Arecaceae) is the most highly attacked palm species at Balboa Park, and importantly, no attacks on the edible date palm, Phoenix dactylifera L. (Arecaceaae), have been observed. The edible date industry is an important specialty crop in California that may be at risk from R. palmarum. Sumario Cuatro especies de palmeras, anteriormente hospederas desconocidas de Rhynchophorus palmarum L. (Coleoptera: Curculionidae), fueron matadas por este picudo invasor de las palmeras en el Parque Balboa, condado de San Diego, California, EE. UU. Las 4 nuevas especies de palmeras registradas como hospederas reproductoras de R. palmarum por primera vez son Brahea edulis, Jubaea chilensis, Phoenix reclinata, y Sabal bermudana (todas Arecaceae). Phoenix canariensis Chabaud (Arecaceae) es la especie de palmera mas atacada en el Parque Balboa y lo que es mas importante, no se han observado ataques a la palmera datilera comestible, Phoenix dactylifera L. (Aracaceae). La industria de los datiles comestibles es un cultivo importante de especialidad en California que puede estar en riesgo por R. palmarum. Key Words: Brahea edulis; invasive pest; Jubaea chilensis; palm; Phoenix reclinata; Sabal bermudana View this article in BioOne

Brown marmorated stinkbug (BMSB), Halyomorpha halys Stal (Hemiptera: Pentatomidae), is native to Asia and an invasive urban and agricultural pest in the US. In California (CA), BMSB has been recorded attacking specialty crops such as almonds and peaches. The egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), a key BMSB natural enemy native to Asia, is a candidate for classical biological control efforts targeting BMSB in CA and other parts of the US Trissolcus japonicus cannot be introduced deliberately into CA for BMSB control without US federal regulatory agency approval which is contingent on better understanding of its host range and specificity. Consequently, the host specificity and physiological host range of T. japonicus was evaluated under laboratory quarantine conditions by exposing eggs of BMSB and non-target pentatomid hosts (native and other exotic species) found in CA to T. japonicus. No-choice and binary-choice experiments provided female T. japonicus with equal unrestricted access to eggs of BMSB and non-target pentatomids. In addition to BMSB, eggs from six of ten resident pentatomid species found in CA were parasitized by T. japonicus. However, T. japonicus attack and emergence rates were consistently higher on BMSB when compared to non-target species. These results suggest that T. japonicus is oligophagous, but BMSB is a superior reproductive host compared to non-target pentatomid species that were evaluated. The implications of these findings for classical biological control efforts targeting BMSB in CA are discussed.

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is an invasive pest which presents a major economic threat to grape industries in California, because it spreads a disease-causing bacterium, Xylella fastidiosa. In this note we develop a time and temperature dependent mathematical model to analyze aggregate population data for H. vitripennis from a 10-year study consisting of biweekly monitoring of H. vitripennis populations on unsprayed citrus, during which H. vitripennis decreased significantly. This model was fitted to the aggregate H. vitripennis time series data using iterative reweighted weighted least squares (IRWLS) with assumed probability distributions for certain parameter values. Results indicate that the H. vitripennis model fits the phenological and temperature data reasonably well, but the observed population decrease may possibly be attributed to factors other than the abiotic effect of temperature. A key factor responsible for this decline but not analyzed here could be biotic, for example, potentially parasitism of H. vitripennis eggs by Cosmocomoidea ashmeadi. A biological control program targeting H. vitripennis utilizing the mymarid egg parasitoid Cosmocomoidea (formerly Gonatocerus) ashmeadi (Girault) is described.

Androdioecy (the coexistence of males and hermaphrodites) is a rare mating system for which the evolutionary dynamics are poorly understood. Here we study the only presumed case of androdioecy in insects, found in the cottony cushion scale, Icerya purchasi. In this species, female-like hermaphrodites have been shown to produce sperm and self-fertilize. However, rare males are sometimes observed too. In a large population-genetic analysis, we show for the first time that although self-fertilization appears to be the primary mode of reproduction, rare outbreeding events between males and hermaphrodites do occur, and we thereby confirm androdioecy as the mating system of I. purchasi. Thus, this insect appears to have the colonization advantages of a selfing organism while also benefitting from periodic reintroduction of genetic variation through outbreeding with males.

Halyomorpha halys (Stål) is an invasive pest in the United States and other countries. In its native range, H. halys eggs are parasitized by a co-evolved parasitoid, Trissolcus japonicus (Ashmead). In the United States, T. japonicus, a classical biological control candidate, is being redistributed in many states where adventive populations exist. To establish if H. halys egg holding conditions affect T. japonicus foraging behavior or successful parasitism, naïve, female parasitoids from an adventive population were allowed to forage in laboratory bioassay arenas with either fresh or frozen (−20 or −80°C) egg masses, the latter held for five durations ranging from 1 h to 112 d. Parasitoid movements were recorded for 1 h. Thereafter, parasitoids were transferred with the same egg mass for 23 h. Additionally, female parasitoids from a quarantine colony were exposed to: 1) pairs of fresh egg masses and egg masses frozen at −40°C (>24 h) or 2) a single fresh egg mass or egg mass frozen at −40°C (

The efficacies of two trap types, bucket and Picusan traps, for capturing and retaining Rhynchophorus palmarum (L.), an invasive palm pest responsible for killing thousands of ornamental Canary Islands date palms (Phoenix canariensis Chabaud [Arecales: Arecaceae]) in San Diego County, CA, were compared. Digital video data were analyzed to determine how R. palmarum behavior toward each trap type affected capture and retention rates. Videography was conducted 24 h/d, 7 d/wk, for more than 7 mo resulting in 20,211 h of digital data for analysis. Weevil attraction to traps was observed only during daylight hours and no patterns in diel activity were found. Neither trap type tested captured 100% of weevils attracted to traps. Bucket traps suspended 1.5 m above the ground attracted 30% more weevils than ground deployed Picusan traps. Of those weevils attracted to bucket traps, 89% entered, 82% escaped, and 18% that entered traps were retained. Weevils that were not retained spent an average of 19 min 20 s entering and exiting entry holes and walking and flying around the bucket trap. By contrast, Picusan traps captured 89% of weevils that entered the trap. The time between weevils arriving (via walking or flight) on the sides of the Picusan trap and retention in the trap ranged between 90 and 376 s. These visual observations suggest that Picusan traps are more efficient than bucket traps for R. palmarum capture.

Rhynchophorus palmarum (L.) is an invasive pest responsible for killing thousands of ornamental Canary Islands date palms (Phoenix canariensis Chabaud) in San Diego County, CA. Two field experiments were conducted to compare the attractiveness of six different baits and two trap types. The tested baits were dates + water; dates + water + Saccharomyces cerevisiae; dates + water + S. bayanus; dates + water + S. pastorianus; 15% sugarcane molasses water solution mixed with 3% paraffinic oil, and a no bait control treatment. The two traps tested were white bucket traps (hanging 1.5 m above the ground and set on the ground) and black cone shaped Picusan traps (set on ground only). All traps were loaded with commercially available R. palmarum aggregation pheromone and the synergist ethyl acetate. Differences in weevil capture rates were observed across bait and trap types. Weevil captures were almost five times greater in Picusan traps compared to bucket traps that were hanging or placed on the ground. Adding dates and water alone or combined with S. cerevisiae to traps increased weevil captures compared to other baits and controls. Trap and bait types affected bycatch of nontarget arthropod species. In general, spiders, earwigs, and carabid beetles were most commonly recovered from Picusan traps, regardless of bait type. Scarab beetles, moths, and flies were found more frequently in bucket traps baited with molasses or dates mixed with S. bayanus. No effects of bait and trap type were associated with bycatch species richness.

The palm weevil, Rhynchophorus palmarum (L.), was first recorded in San Diego County, CA in 2011 and breeding populations were recovered from infested Canary Islands date palms, Phoenix canariensis, in San Ysidro, San Diego County, in 2015. This palm pest presents a significant threat to California’s edible date industry as Phoenix dactylifera is a recorded host for this weevil. The flight capabilities of R. palmarum are unknown which limits understanding of rates of natural dispersal. In response to this knowledge deficit, 24-h flight mill trials were conducted with field-collected male and female weevils. A total of 87 weevils (49 females and 38 males) were used in experiments, ~6% failed to fly >1 km in 24 h and were excluded from analyses. Of those 82 weevils flying >1 km in 24 h, the average distance flown by males and females was ~41 and ~53 km, respectively. Approximately 10% of females flew >100 km in 24 h, with two (~4%) females flying >140 km. The maximum recorded distance flown by a male weevil was 95 km. Flight activity was predominantly diurnal and flying weevils exhibited an average weight loss of ~18% while non-flying control weevils lost ~13% body weight in 24 h. The combined flight distances for male and female weevils exhibited a heavy-tailed platykurtic distribution. Flight mill data for R. palmarum are compared to similarly collected flight mill data for two other species of invasive palm weevil, Rhynchophorus ferrugineus (Olivier) and Rhynchophorus vulneratus (Panzer).

Western flower thrips, Frankliniella occidentalis, first arose as an important invasive pest of many crops during the 1970s–1980s. The tremendous growth in international agricultural trade that developed then fostered the invasiveness of western flower thrips. We examine current knowledge regarding the biology of western flower thrips, with an emphasis on characteristics that contribute to its invasiveness and pest status. Efforts to control this pest and the tospoviruses that it vectors with intensive insecticide applications have been unsuccessful and have created significant problems because of the development of resistance to numerous insecticides and associated outbreaks of secondary pests. We synthesize information on effective integrated management approaches for western flower thrips that have developed through research on its biology, behavior, and ecology. We further highlight emerging topics regarding the species status of western flower thrips, as well as its genetics, biology, and ecology that facilitate its use as a model study organism and will guide development of appropriate management practices.

Dispersal of natural enemies from buckwheat cover crop plots embedded within a southern California vineyard during spring and summer was investigated by using an arthropod mark-capture technique. Specifically, arthropods were marked in flowering buckwheat plots by spraying plants with a “triple mark” solution containing yellow dye, casein protein, and albumin protein. In turn, we recorded the abundance of marked and unmarked natural enemies at a gradient of distances from the treated buckwheat plots into the vineyard. Natural enemies marked with yellow dye were identified visually, while the presence of casein and albumin protein marks were detected using anti-casein and anti-albumin enzyme-linked immunosorbent assays (ELISA). The percentage of natural enemies marked with yellow dye indicated that spiders, predatory thrips (Aeolothripidae), and minute pirate bugs (Anthocoridae) dispersed 9 m (i.e., 3 rows) from marked buckwheat refuges over a six day period. The percentage of leafhopper parasitoids (Anagrus erythroneurae S. Trjapitzin and Chiappini) marked with yellow dye indicated that 22% of marked parasitoids were captured up to 18 m (i.e., six rows) to 30 m (i.e., 10 rows) from buckwheat plots up to six days after marks were applied to cover crops. Up to 17% of natural enemies marked with yellow dye, albumin, or casein were captured in non-treated control plots, suggesting that parasitoids, spiders, minute pirate bugs and predatory thrips were able to cross the 36 m buffer zones used to separate marked buckwheat plots and unmarked control plots. Results comparing the percentage of parasitoids and ‘other beneficials’ marked with a double mark (where any two of the three marks were detected) between distances in buckwheat plots indicated that double marked parasitoids were found up to 30 m (i.e., 10 rows) from buckwheat refuges, while no double marked parasitoids were captured in control plots. No triple marked arthropods were captured. To exploit the dispersal capabilities of natural enemies, these results suggest that buckwheat refuges planted in California vineyards could be planted every 6th (i.e., 18 m) or 10th (30 m) row to gain potential benefits from providing natural enemies with flowering buckwheat refuges.

Urban areas landscaped with ornamental palms, especially Canary Islands date palms (Phoenix canariensis), are particularly vulnerable to incursion by invasive palm weevils, Rhynchophorus spp. (Coleoptera: Curculionidae). Metropolitan palmscapes are often resource rich in terms of palm species diversity and density, and these areas typically have numerous conduits (e.g., air, road, or sea transportation hubs) that assist with international and regional trade and tourism which can facilitate accidental or deliberate weevil introductions. Once established in urban areas, Rhynchophorus populations may be hard to suppress, from where they can expand their range and threaten agricultural commodities or native palms in wilderness areas. Here, we review current knowledge about relationships between Rhynchophorus invasions and urban environments. Further research areas should be addressed to improve forecasts of invasion risks and to complement management options for detection and control. We propose that greater attention be paid to quarantine restrictions on live palm movements and pro-active early detection and monitoring programs in areas deemed to be at high risk of invasion and establishment. In response to an incursion, we advocate the deployment of containment and eradication campaigns in urban zones when populations are small and highly localized.

Baiting is an effective method to manage Vespula spp. yellowjacket (Hymenoptera: Vespidae) populations without having to locate and treat nests. Here, we assessed the utility of a commercially available polyacrylamide hydrogel as an alternative bait material for yellowjacket baiting. The experimental bait (hereafter referred to as 'hydrogel bait') consisted of diluted chicken juice (from canned chicken meat) and fipronil (0.025%, wt/wt) absorbed into granular polyacrylamide hydrogel particles. Three separate 24-h baiting trials were conducted at two different field sites with the western yellowjacket, Vespula pensylvanica (Saussare), as the target species. The monitoring data from pre- and posttreatment periods indicated that baiting with polyacrylamide hydrogel baits provided ≈74-96% reduction in the foraging activity of V. pensylvanica during its active season. In addition to their ability to absorb large quantities of aqueous bait containing phagostimulants and toxicants, the hydrogels' tactile resemblance to fresh meat upon hydration makes them a promising option as a non-meat material for delivering small amounts of insecticides to yellowjacket populations in a highly targeted manner.

The brown marmorated stinkbug (BMSB), Halyomorpha halys Stal (Hemiptera: Pentatomidae), is native to Asia and is characterised by its polyphagous feeding habits and high hitchhiking potential. In i...

The Asian citrus psyllid, Diaphorina citri, is a significant economic pest of citrus because it vectors a bacterium that causes the lethal citrus disease huanglongbing. From 2015 to 2016, digital video recorders were used to identify natural enemy species attacking sentinel immature D. citri colonies deployed monthly at three urban sites in southern California. Natural enemy activity during both daylight and nighttime hours was recorded. To examine the impact of ant-hemipteran mutualisms on biological control efficacy, we compared natural enemy interactions with D. citri colonies that were either fully exposed or protected from walking arthropods with a sticky barrier. Spiders (Aranae), syrphid larvae (Syrphidae), predatory mites (Phytoseiidae), green lacewing larvae (Chrysopidae), thrips (Thripidae), and the introduced parasitoid, Tamarixia radiata, were the dominant natural enemy groups visiting immature D. citri colonies over the course of the study. A significant proportion of syrphid and green lacewing larvae, and T. radiata visits to the sentinel colonies resulted in D. citri attacks. Spiders rarely attacked immature D. citri. Argentine ants, Linepithema humile, were the most common arthropod visiting D. citri colonies across all study sites and ants were active day and night. When ant access to D. citri colonies was restricted, natural enemy abundance and attack rates increased, particularly those by syrphids and T. radiata. This study highlights the importance of natural enemies and ant-psyllid interactions in the biological control of D. citri in urban citrus ecosystems. Therefore, conservation of natural enemies and ant control should be considered for the sustainable management of this pest-disease complex.

Tamarixia radiata parasitizes nymphs of Diaphorina citri, a global citrus pest that vectors a bacterium that causes a lethal citrus disease, huanglongbing. The effects of four species of potted flowering native California plants, potted flowering buckwheat (Fagopyrum esculentum) and Euphorbia marginata (both non-native), honeydew from D. citri and Coccus hesperidum, cut flowers from lemon and orange trees, 50% honey-water, and water only on the longevity, survivorship and reproduction of T. radiata was investigated in the laboratory. Fecundity was measured by counting egg load of parasitoid cohorts ~15 h of age at time of set up and those that were removed for dissection from test arenas at 1, 6, and 18 days after introduction, or at time of death. Maximum survival of female T. radiata was 34 days on honey-water. Survival on honey-water, buckwheat and C. hesperidum honeydew was statistically equivalent, and these three food treatments significantly enhanced parasitoid survival when compared with all remaining food treatments. Female T. radiata fed on D. citri honeydew survived an average of 5 days, which was 3 days longer, on average, than those provided with water only. Parasitoid egg load significantly decreased with increasing days alive, thereby demonstrating the synovigenic nature of T. radiata. Parasitoids that fed on buckwheat flowers and died from natural causes had, on average, 5 more mature eggs in their ovaries at time of death when compared to parasitoids that died when provided access to other experimental sugar sources that were tested. These results suggest that buckwheat may be a useful insectary plant in citrus orchards that could enhance the efficacy of T. radiata against D. citri.

The effects of climate and ants on population regulation of an invasive citrus pest, Diaphorina citri (Hemiptera: Liviidae), by its parasitoid Tamarixia radiata (Hymenoptera: Eulophidae), in southern California were examined over a four-year period. Densities of D. citri eggs, nymphs, and adults, and Argentine ant, Linepithema humile (Hymenoptera: Formicidae), a mutualist which defends psyllid nymphs from natural enemies, citrus flush growth patterns, and parasitism rates of T. radiata, were monitored every four weeks on grapefruit, lemon, lime, orange, and tangerine trees at 28 urban sites across three climate types (coastal, intermediate, and desert). Significant spatial and temporal effects on D. citri abundance and parasitism rates were observed over this four-year period. Highest D. citri densities and parasitism rates were found in the intermediate and coastal regions during peaks of flushing cycles of citrus plants over March-June and September-November each year. Over the course of this study, population densities of D. citri declined by over 75%. Parasitism by T. radiata was identified as a significant mortality factor often exceeding 60% during periods of peak parasitoid activity. Analyses indicated that parasitism resulted in delayed density-dependent mortality and subsequent reductions in D. citri densities lagged by ~ 1 yr. Trends in D. citri densities and parasitism rates over time were similar on grapefruit, lemons, limes, oranges, and tangerines. Presence of L. humile in citrus resulted in a 3-fold increase in D. citri densities and control of this pest ant is needed to maximize biological control of D. citri.

Diaphorina citri (Hemiptera: Liviidae) is a notorious citrus pest that vectors a bacterium that causes huanglongbing, a lethal citrus disease. Studies evaluating the potential of buckwheat (Fagopyrum esculentum), alyssum (Lobularia maritima), phacelia (Phacelia tanacetifolia), and California poppy (Eschscholzia californica) as insectary plants for conservation biological control of D. citri were conducted in California citrus orchards. Field studies assessed flowering phenology and attractiveness to hoverflies and other natural enemies, hoverfly oviposition on D. citri colonies, and the effect of potted alyssum and predation from hoverflies on the mortality of D. citri nymphs. Laboratory studies quantified lifetime consumption of D. citri nymphs by individual Allograpta obliqua (Diptera: Syrphidae) larvae, the only hoverfly species attacking D. citri in the field. Results indicated that alyssum and buckwheat possessed a short sowing to flowering time (30–33 days when sown in March) and attracted 10–20 times more syrphids than California poppy. No hoverflies were observed feeding from phacelia. California poppy was marginally attractive to hoverflies, and failed to attract ladybugs, parasitoids, or predatory wasps. When alyssum was present in an unsprayed citrus orchard, the number of hoverfly eggs laid on D. citri colonies and abundance of predators was 3.5 times and 2.5 times higher, respectively, when compared to control plots lacking alyssum. Consequently, 10% more D. citri nymphs survived to adulthood in the control plots compared to alyssum plots. In the laboratory, individual A. obliqua larvae consumed, on average, 421 D. citri nymphs before pupation. Results demonstrate that A. obliqua is an important and voracious predator of D. citri nymphs, and that alyssum and buckwheat show potential as insectary plants for conservation biological control of D. citri.

During the winter of 2014–15 in southern California, attempts were made to accelerate immature brown recluse spiders, Loxosceles reclusa Gertsch & Mulaik, 1940, to maturity for a pest control experiment in early spring. Despite food offerings, spiders stopped molting after October although they were maintained at 25° C and had swollen, well-nourished abdomens. It was surmised that decreased filtered daylight from a paper-covered window might be suppressing molting. Feeding was halted in January 2015; 88 spiderlings were checked weekly for molts. Molting resumed during late March 2015 and continued through May 2015 despite no feedings. To more thoroughly elucidate photoperiod effects on molting, during the week of the September 2015 equinox, three cohorts of 10 immatures of both brown and Chilean recluses, L. laeta (Nicolet, 1849), were exposed to three light regimes: 14:10 L:D, natural, 10:14 L:D. Through November 2015 to late March 2016 for brown recluses, there was no molting in the 10:14 regime, 3 of 10 spiders molted in the natural light regime, and 8 of 10 spiders molted in the 14:10 L:D regime. Additionally, fifteen newly-emerged brown recluse spiderlings split into three cohorts of 5 spiders each in November exhibited more molting in the 14:10 L:D compared to natural and 10:14 L:D light cycles. Chilean recluses showed no differences in molting across the three photoperiod regimes. This species difference may be explained in that brown recluses are native to temperate zones where winters can be fatal; Chilean recluses are tropical where short photoperiods may have little significance for survival.

Oligonychus perseae Tuttle, Baker & Abbatiello (Acari: Tetranychidae) is an economically important foliar pest of avocados from Mexico. Invasive O. perseae populations became established throughout the commercial avocado system in California (USA) during the early 1990s, but the putative geographic origin(s) of the California O. perseae populations has not been investigated. To address this shortcoming, a series of population genetic analyses for O. perseae populations representative of a broad geographic sample range was conducted. This study identified a single mitochondrial cytochrome c oxidase subunit I (COI) haplotype match between O. perseae populations collected in California with those from 4 municipalities in Michoacan, Mexico, part of the presumptive native range of this pest. Interestingly, this haplotype also was collected from avocados at 2 locations in Baja California, Mexico, and it was identified from a representative sample from Israel where O. perseae is an invasive avocado pest. Molecular data confirm the likely Mexican origin of invasive O. perseae populations in California, and may help delimit the geographic area to be searched for coevolved natural enemies of O. perseae that could be introduced into California as part of a future classical biological control program targeting this pest. Moreover, molecular results uncovered significant and concordant genetic divergence in both mitochondrial (COI) and ribosomal DNA markers, i.e.,internal transcribed spacer 2 (ITS2) and a section of the 28S gene region, pointing to the potential occurrence of a cryptic species complex within O. perseae. The implications of these findings on future taxonomic and molecular work for O. perseae are discussed.

Two parasitoids attacking nymphs of Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) and Diaphorencyrtus aligarhensis (Shafee, Alam & Agarwal) (Hymenoptera: Encyrtidae) are being released in California, USA in a classical biological control program. To evaluate the effect of multiple parasitoid species on D. citri mortality, we conducted mesocosm experiments under controlled conditions using a complete block design with 6 treatments (D. citri nymphs exposed to: no parasitoids; D. aligarhensis or T. radiata alone; D. aligarhensis or T. radiata released first (by 48 h); and both species released simultaneously). Parasitism of D. citri nymphs by T. radiata exceeded 60% and was unchanged when D. aligarhensis were present. Parasitism by D. aligarhensis was greatest when T. radiata was absent (∼28%) and was reduced in all treatments with T. radiata present (

BACKGROUND Insecticide sprays used for ant control cause environmental contamination. Liquid bait is a safe and effective alternative, but it requires bait stations to dispense the toxicant. We developed a biodegradable hydrogel to deliver liquid bait obviating the need for bait stations. RESULTS Alginate hydrogel beads with preferred rigidity and maximum hydration in 25% sucrose solution were engineered by optimizing a crosslinking process. The moisture content of the substrate on which the beads were placed and the relative atmospheric humidity significantly influenced water loss dynamics of the hydrated hydrogel beads. Laboratory choice studies indicated that hydrated hydrogel beads had reduced palatability to foraging ants when they lost ≥ 50% water. An enzyme linked immunosorbent assay (ELISA) indicated that the insecticide thiamethoxam added to sucrose solution was absorbed into the hydrogel beads. Hydrogel beads conditioned in sucrose solution with 1 mg L−1 thiamethoxam provided complete control of all castes of Argentine ant Linepithema humile (Mayr) colony by 14 days post-treatment in the laboratory trial and provided a 79% reduction in ant activity after 8 weeks in the field trial. CONCLUSION Alginate hydrogel beads provided an effective delivery system for liquid baits laced with low concentrations of insecticide to control Argentine ants.

Direct observation was used to construct activity budgets for Diaphorencyrtus aligarhensis (Shafee, Alam & Agarwal) (Hymenoptera: Encyrtidae) and Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), foraging for nymphs of Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Two populations of D. aligarhensis were used in experiments: a biparental population from Pakistan and a uniparental population from Taiwan. Parasitoids were provisioned with 20 D. citri nymphs, second through fifth instar; female parasitoids from all three populations foraged alone, in conspecific pairs, or in heterospecific pairs. Walking occupied approximately 40% of the activity budget of D. aligarhensis and ovipositor probing occupied 10–20%. In contrast, probing and walking each accounted for approximately 30% of the activity budget of T. radiata. The presence of conspecific females affected the activity budget of D. aligarhensis females, such that the focal female was observed walking less often and...

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a significant citrus pest and the parasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) has been released in various citrus-producing areas in classical biological control programs targeting D. citri. We investigated the effect of host deprivation on the foraging behavior and patch utilization by T. radiata. In the laboratory, females deprived of hosts for 3 days tended to leave patches of 12 nymphs without parasitizing hosts during the ca. 30 min they spent in the patch before leaving. Moreover, half of these females failed to host feed, and those that did host feed, on average, needed more than 15 min to complete feeding. Conversely, non-host-deprived females parasitized on average three nymphs before leaving patches without host feeding during the ca. 39 min they spent in the patch. These laboratory observations were compared to mass-reared female T. radiata that were released onto colonies of D. citri nymphs infesting citrus in the field. Release vials were provisioned with honey and these females had no opportunities to host feed over the 1- to 2-day containment period prior to release. When introduced onto D. citri colonies, 68% T. radiata females abandoned D. citri patches prior to probing hosts, in part, because Argentine ants, Linepithema humile (Mayr) (Hymenoptera: Formicidae), tending colonies disturbed searching parasitoids. These results from laboratory and field studies are discussed in the context of classical biological control, with the aim of understanding how to manipulate host availability and ant activity so establishment rates and impact of T. radiata can be improved.

A series of 15 species described from specimens collected from the leaves of mango trees at a single site in Mexico are newly placed as synonyms of the California citrus thrips, Scirtothrips citri (Moulton) (Thysanoptera: Thripidae). These species were originally discriminated based on differences in the precise placement of setae in the median area of the pronotum, and this chaetotaxy is here recognized as variable within populations of this thrips from various sites in California and Mexico. Preliminary results from molecular analysis of 2 genes, CO1 and 28S-D2, indicate that there is variation at the molecular level between populations of S. citri. However, this variation is not sufficient to support new species designations, and no consistent morphological divergence between these populations was detected. ResumenUna serie de 15 especies descritas de especimenes recolectadas sobre hojas de arboles de mango en un solo sitio en Mexico han sido recientemente colocadas como sinonimos deltrips de los citricos de California, Scirtothrips citri (Moulton) (Thysanoptera: Thripidae). Estas especies fueron descriminadas originalmente basado en las diferencias en la colocacion precisa de las setas en la zona media del pronoto y esta quetotaxia esta aqui reconocida como variable dentro de las poblaciones de este trips de varios sitios en California y Mexico. Los resultados preliminares de analisis molecular de 2 genes, CO1 y 28S-D2, indican que hay una variacion en el nivel molecular entre las poblaciones de S. citri. Sin embargo, esta variacion no es suficiente para soportar las nuevas designaciones de especies, y no se detecto ninguna divergencia morfologica consistente entre estas poblaciones. View this article in BioOne

Proactive biocontrol could accelerate responses to invasive pests in urban areas — where pesticide use may be unpopular — before they spread to agricultural areas.

The glassy-winged sharpshooter, Homalodisca vit-ripennis, is an invasive pest which presents a major economic threat to grape industries in California, as well as Texas [24] and other wine growing regions, because it spreads a disease-causing bacterium, Xylella fastidiosa. We continue an earlier investigation [1] into a long-term phenological decline of H. vitripennisdensities by studying a system of delayed differential equations (DDEs). We analyze aggregate population data for H. vitripennisfrom a 10-year study in which bi-weekly monitoring of H. vitripennispopulation numbers significantly decreased. These data present several challenges for modelers. First, they involve truly aggregate population level sampling and hence cannot properly be treated as ordinary longitudinal time series data corresponding to individual level models. The appropriate modeling involves estimation of probability distributions for parameters rather than estimation of the dynamic parameters themselves. Moreover, our analysis reveals that the correct corresponding statistical models involve errors that are observation size dependent (e.g., relative errors should be employed in statistical models). We use these data to test whether DDEs are useful in modeling the observed H. vitripennispopulation decline. To do this, we perform an analysis of variance (ANOVA) type test comparing the glassy-winged sharpshooter (GWSS) model with delay to a model without delay. The model is fit to the aggregate H. vitripennisdata using iterative reweighted weighted least squares (IRWLS) by estimating probability densities over the delay and one of the egg developmental rate parameters. Results indicate that a positive delay provides improvement with a significance level of $P •

Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an invasive citrus pest in California that vectors a bacterium that causes the deadly citrus disease huanglongbing. From 2014–2015, 116 experimental D. citri cohorts were monitored to determine survivorship, life table parameters, and marginal rates of mortality of immature D. citri at three sites in Riverside County, CA. D. citri cohorts of ∼200 eggs were established on potted Citrus volkameriana (Rutaceae) plants. Field deployed cohorts were protected with fine or coarse mesh enclosures, sticky barriers, or left unprotected. Egg through adult emergence rates were used to assess the relative importance of biotic and abiotic factors on psyllid survivorship rates by life stage. Predation of immature D. citri by larvae of Allograpta sp. (Diptera: Syrphidae) and Chrysoperla sp. (Neuroptera: Chrysopidae) comprised 86% of all observed predation mortality. When protected from all other arthropods, parasitism by Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) comprised 21% of the total marginal rate of immature D. citri mortality from September to November in 2014 and 2015. Overall, D. citri net reproductive rates were reduced by 55–95% when exposed to natural enemies, indicating the importance of the classical biological control agent, T. radiata , and generalist predators in reducing D. citri densities in urban areas of southern California.

In October 2010, Rhynchophorus vulneratus, originally identified as the red palm weevil, R. ferrugineus, was discovered infesting Canary Island date palms in Laguna Beach, California. The red palm weevil has caused extensive mortality of palms in the Mediterranean, the Middle East and North Africa, and its discovery in California caused concern for the state's ornamental palm and date industries and the many palms in Southern California landscapes. A rapid, coordinated effort led to the deployment of traps baited with the weevil's aggregation pheromone, coordinated pesticide applications to privately owned palms and destruction of palms at advanced stages of infestation. Research confirmed the chemical components of the aggregation pheromone, assessed the efficacy of trapping strategies and resolved the taxonomic identity, native range and putative region of origin for the population detected in Laguna Beach. The last confirmed detection of a live R. vulneratus was Jan. 20, 2012. USDA-APHIS declared this weevil eradicated from California on Jan. 20, 2015. The estimated cost of the eradication was $1,003,646.

Research on phytoseiid mites has been critical for developing an effective biocontrol strategy for suppressing Oligonchus perseae Tuttle, Baker, and Abatiello (Acari: Tetranychidae) in California avocado orchards. However, basic understanding of the spatial ecology of natural populations of phytoseiids in relation to O. perseae infestations and the validation of research-based strategies for assessing densities of these predators has been limited. To address these shortcomings, cross-sectional and longitudinal observations consisting of >3,000 phytoseiids and 500,000 O. perseae counted on 11,341 leaves were collected across 10 avocado orchards during a 10-yr period. Subsets of these data were analyzed statistically to characterize the spatial distribution of phytoseiids in avocado orchards and to evaluate the merits of developing binomial and enumerative sampling strategies for these predators. Spatial correlation of phytoseiids between trees was detected at one site, and a strong association of phytoseiids with elevated O. perseae densities was detected at four sites. Sampling simulations revealed that enumeration-based sampling performed better than binomial sampling for estimating phytoseiid densities. The ecological implications of these findings and potential for developing a custom sampling plan to estimate densities of phytoseiids inhabiting sampled trees in avocado orchards in California are discussed.