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Aromatic plants can affect arthropod community composition and reduce herbivore populations by attracting beneficial insects such as generalist predators. To investigate the possible mechanisms underlying the attraction of aromatic plant species to natural enemies in the field, we assessed the attractiveness of Ocimum basilicum L. (basil), Mentha piperita L. (peppermint), Melissa officinalis L. (lemon balm) (Lamiaceae) and Cordia verbenacea DC (black sage) (Boraginaceae) to adults of the green lacewing Ceraeochrysa cubana Hagen (Neuroptera: Chrysopidae), a generalist predator widely distributed across the Americas. Additionally, we tested whether access to leaves and flowers of these plant species would affect larval survival, development or oviposition by C. cubana . The green lacewing was attracted to basil but not to the other aromatic plants. Larvae and adults did not benefit from the presence of any plant leaves, but basil flowers enhanced C. cubana larval and adult survival. Basil can be recommended as a companion crop in conservation biological control programs, not only for its well-known negative effects on pests, but also for its attractiveness to generalist predatory insects such as C. cubana . Besides attracting adults, basil flowers benefit both larvae and adults, which is desirable for conservation biological control.

As part of a USDA Specialty Crop Research Initiative project to enhance biological control (BC) in western U.S. orchard systems, we surveyed walnut growers in California and pear growers in Oregon and Washington about their pest management decision-making and use of BC practices. Seventy-six percent of pear growers and 54% of walnut growers reported using one or more BC practices. BC users were more likely to minimize factors that harm natural enemies than enhance natural enemy habitats or release commercially produced natural enemies. Walnut growers with more education and orchard experience, as well as larger and more diversified operations, were more likely to use BC practices. Walnut and pear growers with some certified organic acreage, who considered environmental impacts when making pest management decisions, and who used selected pest management practices (pheromone mating disruption and degree-day calculations for codling moth control) were more likely to use BC practices. BC users relied more heavily on industry publications and university-based sources of pest management information, compared with non-users. The perceived benefits of BC adoption included reduced reliance on pesticides, reduced production costs, environmental protection, protection of beneficial insects, and improved worker safety and human health. The perceived barriers to BC adoption included lack of knowledge, questionable effectiveness, high cost, and lack of recommendation by pest management consultants. Our research not only contributes to the literature on the adoption of sustainable agricultural practices, but also can inform future BC research and outreach by offering insight into who uses BC practices and assessment of perceived adoption benefits and barriers.

The effect of an irrigated buckwheat cover crop on populations of beneficial insects and grape pests, vine growth, grape yield, and berry quality was investigated over 1 year in a commercial organic vineyard in southern California, USA. Buckwheat was grown in the spring and summer with additional irrigation that supplemented prevailing vine watering regimens. Treatments replicated four, three and six times respectively were: (1) buckwheat cover crop with supplemental irrigation between vine rows; (2) supplemental irrigation with no buckwheat cover crop; and (3) control plots with no buckwheat cover crop or supplemental irrigation. Flowering buckwheat was extremely attractive to beneficial insects at the beginning of the trial, resulting in 27 times more insects captured from shake sampling, compared with grape foliage in control plots. Results from sticky trap and visual count data indicated that buckwheat may enhance the abundance of generalist predators at certain times. However, densities of pestiferous leafhoppers on grape leaves in August was significantly higher (129–240% greater) in irrigated buckwheat and irrigated plots lacking buckwheat when compared with control plots. This increase in leafhopper density may be attributed to these pests preferring well-irrigated, vigorously growing vines. Mean cane weight was 222% and 170% greater for vines in irrigated buckwheat and irrigated plots lacking buckwheat, respectively, compared with controls indicating that vine vigor increased with supplemental irrigation. An irrigated buckwheat cover crop increased berry size, on average, by 0.67 mm for berries harvested on the side of the row that contained buckwheat, and reduced sugar content of berries by 3.2° Brix, compared with non-irrigated controls. Additionally, the buckwheat cover crop was associated with reduced berry quality because of insect feeding damage. Under drought conditions and water shortages, supplemental irrigation to support cover crops may result in water use penalties. Irrigated cover cropping during summer months may not be a viable pest management option for grape growers in southern California.

Providing nectar and pollen through the establishment of insectary plants is one approach to conserving natural enemies and enhancing biological control of arthropod pests. Recent studies show that natural enemy performance may be influenced by the diversity of insectary plant species and the resources they provide. We conducted laboratory assays to investigate the influence of buckwheat (Fagopyrum esculentum Moench.) and cowpea (Vigna unguiculata (L.) Walp.) alone and in a mixture on the performance of the insidious flower bug, Orius insidiosus (Say, 1832). We measured performance as longevity, fecundity and predation of O. insidiosus reared on a laboratory diet of Ephestia kuehniella or its field prey, Ostrinia nubilalis (Hubner). O. insidiosus survived on average 20–25% longer and oviposited 67–88% more eggs when provided with either insectary species compared to a water only control. However, when provided with a biculture of cowpea and buckwheat, O. insidiosus survived 35% longer and laid 111% more eggs compared to the water only control, with a strong preference for cowpea as an oviposition host. This study provides novel empirical evidence that cowpea, a plant anecdotally cited for its insectary properties, functions as a preferred oviposition sites compared to buckwheat and laboratory standard green beans. The presence of insectary resources, however, did not significantly influence predation on O. nubilalis sentinel prey by O. insidiosus as we anticipated. These results indicate that the performance of beneficial insects like O. insidious may be differentially influenced by the resources provided by insectary species and should be screened for potential benefits before establishing in field settings. Further implications of plant diversification for conservation biological control are discussed.

The use of “insectary strips” of sunflowers and buckwheat is widely promoted by organic certifiers to promote control of the green peach aphid (Myzus persicae) and other pests in organic tobacco. However, no published research supports this recommendation in tobacco, and results from other crops are mixed. We performed a series of experiments to test the effects of non-crop plantings of sunflowers and buckwheat on key pest and beneficial insects adjacent to organic tobacco fields in North Carolina. Although some reduction in M. persicae infestations and increases in numbers of beneficial insects were observed on tobacco plants near field-edge insectary treatments, these effects were small and were observed only over a short distance into the crop. Planting additional insectary strips in the field interior did not reduce aphid numbers in comparison to control treatments and led to increases in some pest insects. These conservation biological control techniques are unlikely to be a reliable method of controlling M. persicae and other pest insects in organic tobacco.

As earwigs (Insecta: Dermaptera) are considered both effective predators of aphids and pests in their own right in citrus orchards, the aim of the present study was to examine their relative role as pest versus predator. We conducted a two-year experiment of earwig exclusion from citrus canopies and compared aphid infestation, flower survival and fruit yield in trees with earwigs (control trees) with those in trees without earwigs (banded trees). However, as not only earwigs but also all other crawling insects were excluded from the banded trees, we added a third group of trees (earwig trees) where crawling insects were excluded but earwigs were added to the canopy every 1–2 weeks. We hypothesized that if the same results were obtained in control and earwig trees, and both differed from those obtained in banded trees, earwigs would most probably be the cause of these differences. Overall, aphid infestation in trees with earwigs was less severe than aphid infestation in trees without earwigs; we also found that aphid density was negatively related to earwig abundance. Earwigs also negatively influenced flower survival but this effect was no longer observed once trees naturally abscised their own flowers and fruitlets. Finally, we did not find any difference in fruit yield between the treatments, or any relationship between earwig abundance and fruit production. Thus, as earwigs appeared to control aphid populations while not affecting fruit yield, we can conclude that earwigs are beneficial insects in this Mediterranean organic citrus orchard.

Insects require small amounts of dietary trace elements because they serve as antioxidants, enzyme co-factors and as constituents of metalloproteins. We measured the levels of 10 trace elements (Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se and Zn) in the predatory insect, Podisus maculiventris, reared on natural prey and artificial diet; two food sources that differed in levels of trace elements. The levels of the trace elements varied greatly in insects reared on the two food sources and differed from the concentrations in the food. We also found that most of the trace elements in the eggs were present in low concentrations and in near-equal amounts in eggs laid by females reared on either of the two food sources. The homeostatic level of most trace elements in the eggs may reflect a commitment by the female to minimize the effect of dietary variation on her offspring. We conclude that trace element levels in P. maculiventris are substantially affected by the food source and can vary significantly from levels in the food source. Knowing this will improve the ability of researchers to determine optimal dietary requirements in insects for trace elements. Additionally, achieving the optimum trace element content within beneficial insects may improve their performance when used in biological control efforts.

Providing floral resources in and around crops enhances local hoverfly populations and recent work has identified a number of key flower species as important sources of pollen and nectar for the adult flies. However, the effects of different flower species on hoverfly fitness have never been studied. In the present work, laboratory experiments were conducted to determine the effectiveness of six flowering plant species in enhancing the longevity and several parameters related to fecundity of Episyrphus balteatus (De Geer). Coriander was the most efficient in terms of the proportion of females laying eggs. Buckwheat gave the highest mean longevity, which correlated with the longest egg-laying duration. However, phacelia increased oviposition rate and lifetime fecundity to the greatest extent, and was responsible for the optimal reproductive potential of female E. balteatus. There was no correlation between pollen and nectar consumption or between the quantity of pollen ingested and the resulting female performance. This suggests that recording the presence of pollen in the diet is not an adequate method to evaluate hoverfly preference or pollen nutritional value. If only one floral resource subsidy is being considered for introduction into agricultural and horticultural systems to enhance hoverfly efficacy, phacelia is recommended, at least for E. balteatus.

Resources for natural enemies are often lacking in agricultural fields. The provisioning of floral resources in crop fields can ameliorate this problem by providing nectar and pollen to natural enemies. To select an appropriate floral resource, plants must be screened for their flowering times and attractiveness to natural enemies and pests. We tested the attractiveness of nine species of annual flowering plants to hoverflies, which are important predators of aphids in California lettuce fields. We also sampled arthropods in the foliage of tested plants, to assess the abundances of other natural enemy and pest species that were present. Tested plants included three commonly-used insectary plants and six flowering plant species that showed potential as either harvestable herbs or cut flowers. Harvestable insectary plants may provide additional economic incentive for growers to set aside land for floral resources. The commonly-used insectary plant sweet alyssum consistently attracted the most hoverflies and the least bees, while potentially harvestable plants attracted few hoverflies. Competition with bees may have reduced hoverfly visits to several of the tested plant species. Sweet alyssum also stayed in bloom the longest, and contained the highest numbers of predatory hemipterans. Results suggest that plants should be screened for their attractiveness to not only the target biological control agent, but also to other potential competitors for floral resources. While this initial study focused on a limited selection of harvestable annual plants, a wide variety of other marketable plant species, particularly perennials, remain to be tested for their attractiveness to hoverflies or other beneficial arthropods.

Augmentative biocontrol constitutes a safe option to reduce pest populations through the enhancement of natural enemies’ activity. In this context, the aphidophagous syrphid Episyrphus baltetaus (De Geer) (Diptera: Syrphidae) is a promising candidate for aphid biological control: larvae of this syrphid attack and consume a wide range of aphid species and are found on many vegetable crops. Because natural populations of beneficial insects are not always sufficient to regulate the pest infestations, this work has focused on the conception of a biological control device containing syrphid eggs which ones can easily be introduced in fields or greenhouses. Using semiochemicals [E-(β)-farnesene, R-(+)-limonene and (Z)-3-hexenol], honeydews and “artificial honeydews” (10% or 30% aqueous solutions of sucrose, fructose and glucose), the syrphid oviposition was artificially induced on an inert surface. Specifically, E-(β)-farnesene and concentrated mono-sugars (30%) were identified as the most efficient ovipositional stimulants. To test and validate the biological control device described above, laboratory and field experiments were performed: a plastic lamella covered with syrphid eggs was suspended on aphid infested plants in order to measure the efficiency of the device. The results obtained were promising since populations of 500 aphids were eliminated in 10 days when 15 syrphid eggs were introduced. The use of such a biological control device could certainly contribute to the biological control to reduce the aphid infestations.

For the mass production of the mirid predator Macrolophus pygmaeus eggs of the Mediterranean flour moth Ephestia kuehniella are routinely used as an effective but expensive factitious food. In the current study, the potential of pollen as a supplementary food for M. pygmaeus was investigated. In a first experiment, the minimum amount of E. kuehniella eggs needed for optimal development and reproduction was determined to be 40 eggs per individual per 3 days. Then, different amounts of E. kuehniella eggs were offered to individual nymphs, supplemented or not with frozen moist honeybee pollen. Insects reared on only 10 E. kuehniella eggs per 3 days suffered higher mortality, developed slower and had lower adult weights and oocyte counts than insects reared on 40 E. kuehniella eggs or 10 eggs supplemented with pollen. When the nymphs were fed only pollen, survival rates and oocyte production were lower than when both pollen and flour moth eggs were provided. On pollen alone, ca. 80% of the nymphs successfully reached adulthood; their adult weights and oocyte counts were, respectively, 12% and 32% lower compared with individuals fed optimal amounts of flour moth eggs. When an egg yolk-based artificial diet was supplemented with bee pollen, development and fecundity were better than on the artificial diet alone. The practical implications of pollinivory for the mass production and the use of this beneficial insect in augmentative biological control programs are discussed.

Long-term storage could aid in the cost-effective mass production of beneficial insects. Pre-conditioning, insect developmental stage and environmental conditions should be considered when selecting storage conditions in order to obtain the highest performance after storage. We evaluated the influence of nutrient quality on the response of eggs, nymphs and adults of Podisus maculiventris when exposed to two temperatures most likely to be used for long-term storage. Natural prey-fed insects were compared to artificial diet-fed insects. The results of our study showed that eggs survived storage at 10 °C better than 4 °C, and that eggs from diet-fed insects survived storage at 10 °C significantly better than eggs from prey-fed insects. Nymphal survival of cold storage treatment was slightly higher than for eggs, with a similar pattern of response to temperature, nutrient quality and time of storage. However, of the three developmental stages tested, the best survival was obtained with adults. Similar to eggs and nymphs, adults survival was higher at 10 °C. However, different from eggs and nymphs was that the prey-fed adults survived better than diet-fed adults. Our results show that prey-fed adults were able to withstand cold storage at 10 °C for 4 weeks with very little loss of survival, fecundity or viability of eggs oviposited by those adults. Longer periods of storage resulted in a decline in survival, fecundity and egg viability and that decline was greatest at 4 °C. For the longer intervals of storage at 10 °C, egg viability was highest for eggs from diet-fed adults. Collectively, these results demonstrate an influence of nutrient quality on the response to cold storage at different developmental stages, and that an optimal food source for continuous rearing is not necessarily an optimal food source for cold storage.

The abundance of mymarid parasitoids attacking the two-spotted leafhopper (Sophonia rufofascia [Kuoh and Kuoh]), a polyphagous pest recently adventive to Hawaii, was monitored using yellow sticky cards deployed in several areas on the islands of Kauai and Hawaii. The yellow cards captured Chaetomymar sp. nr bagicha Narayanan, Subba Rao, & Kaur and Schizophragma bicolor (Dozier), both adventive species, and Polynema sp. Haliday, which is endemic to Hawaii (Hymenoptera: Mymaridae). The former two species were most abundant at all sites. On Kauai, there was a negative correlation between the captures of C. sp. nr bagicha and those of Polynema sp. Throughout the season, the increase in parasitoid numbers generally followed the increase in leafhopper numbers. C. sp. nr. bagicha and S. bicolor showed distinct habitat preferences. Removal of Myrica faya Aiton, an invasive weed that is a highly preferred two-spotted leafhopper host, decreased the overall numbers of captured parasitoids, but led to a twofold increase in the ratio of trapped parasitoids/hosts in weed-free areas.

Red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae), are usually considered serious pests. S. invicta workers, however, are voracious predators and are frequently among the most abundant predators in agroecosystems within their range. Unfortunately, fire ant workers may also attack beneficial insects and arthropods. The goal of this study was to quantify the relationship between the abundance of fire ant workers and the abundance of insect pests and their natural enemies in cotton and soybean. In addition, I used path analysis to estimate the direct and indirect effects (potential loss of pest control due to suppression of other natural enemies) of fire ants. Densities of S. invicta workers were negatively associated with all 16 herbivore taxa sampled in cotton and 13 of the 16 herbivore taxa sampled in soybean. These data suggest that red imported fire ants are important predators of the major insect pests of these crops. The abundance of fire ants, however, was also negatively correlated with the densities of 22 of 24 natural enemy taxa in cotton and 14 of 16 natural enemy taxa in soybean. It appears that fire ants are significant intraguild predators of some of the most important biological control agents in these crops. These indirect interactions were often complex because fire ants not only suppressed populations of beneficial natural enemies (i.e., natural enemies that had negative impacts on pest populations), but also suppressed natural enemies that interfered with biological control (i.e., intraguild predators that had net positive effects on pest populations). Detailed experimental work is needed to determine whether the benefits of pest suppression by fire ants outweigh the negative impact of fire ants on natural enemies. © 2001 Academic Press

New cultivars of alfalfa, Medicago sativa L., have been released with glandular trichomes for resistance to potato leafhopper, Empoasca fabae (Harris). Yet, the impact of the glandular trichomes on the primary natural enemy of the leafhopper, Anagrus nigriventris Girault, is unknown. We compared the host searching behavior of the egg parasitoid on four alfalfa clones varying in trichome characters. Female wasps were videotaped on Ranger, a susceptible clone with relatively sparse trichomes, B14, a resistant clone with dense but nonglandular trichomes, and FG12 and FG18, two resistant clones with glandular trichomes. Although the number of leafhopper eggs per stem exposed to wasps did not significantly differ among the four clones, the frequency of foraging and total foraging time were less on the two clones with glandular trichomes than on the two clones with nonglandular trichomes. In addition, an analysis of covariance demonstrated that, although the number of ovipositional probes increased with egg density on a stem, the number of probes on stems with glandular trichomes was significantly less than that on stems without glandular trichomes. The allocation of time by wasps among drumming, probing, and grooming behaviors was similar among the clones. Wasps tended to fly off of clones with glandular trichomes more often than off of clones with nonglandular trichomes. This study suggests that cultivars with glandular trichomes may interfere with host searching by A. nigriventris.

Passiflora mollissima (H.B.K.) Bailey, a South American vine that grows at high altitudes, is the most important weed pest of the upper-elevation rainforests of Hawaii. Mechanical and chemical methods of controlling this weed are impractical and expensive. Natural enemies appear to restrain this member of the Passifloraceae in its native Andean countries, and the introduction of biological control agents to Hawaii is the only viable control method available. Previous surveys of natural enemies of P. mollissima in its native range resulted in the introduction but unsuccessful establishment of two agents, calling for a renewed search for candidate insects. Detailed studies were conducted for 4 years in Venezuela to survey and evaluate insects attacking P. mollissima. Twelve insect species may have an important effect on the growth and reproduction of this target plant. Three bud-feeding species, Zapriothrica salebrosa Wheeler (Diptera: Drosophilidae), a Mycetophila sp. (Diptera: Mycetophilidae), and Pyrausta perelegans Hampson (Lepidoptera: Pyralidae), as well as a fruit feeder, Dasiops caustonae Norrbom and McAlpine (Diptera: Lonchaeidae), limited flower and fruit production and were believed to play the most important role in regulating wild stands of P. mollissima in Venezuela. The mycetophilid and D. caustonae were not collected from previous surveys and are recommended as potential biological control agents.

Seasonal abundance, dispersal, and overwintering of the 12-spotted ladybird beetle, Coleomegilla maculata (DeGeer), in the mid-Atlantic states were investigated to assess the potential to manipulate the habitat of this predator to increase its impact on Colorado potato beetle, Leptinotarsa decemlineata (Say), management in commercial potato plantings. C. maculata populations were highest in corn fields through August, and overwintering aggregations were found most commonly in habitats adjacent to these fields. Although adult and larval populations of C. maculata were synchronized with first-generation potato beetle eggs and small larvae, they were concentrated in wheat rather than potato fields because most of the potato plants had not yet emerged when C. maculata adults dispersed from their overwintering sites. The subsequent generation of C. maculata tended to aggregate in corn rather than potato in late May and early June. Therefore, given the current mixture of crops as well as climatic and marketing limitations on planting date for potatoes, the potential for habitat manipulation to increase the impact of C. maculata on Colorado potato beetle management in potato in the mid-Atlantic states appears to be limited.

The efficiency of blacklight, blacklight blue, cool white light, and plant/aquarium light sources in attracting selected beneficial insects under different moon phases was tested in field experiments in central Missouri between 1 May and 31 October, 1996. Lady beetles (Coleoptera: Coccinellidae) favored the blacklight source, whereas Ophion sp. (Hymenoptera: Ichneumonidae) were significantly more abundant in blacklight blue source. Chrysopa spp. (Neuroptera: Chrysopidae) were equally attracted by cool white, blacklight, and plant/aquarium light lamps. However, damsel bugs (Hemiptera: Nabidae) and Hemerobius spp. (Neuroptera: Hemerobiidae) did not prefer a specific light. Catches of other species (moths and large beetles that mutilate light trap collections) were substantially reduced in traps with cool white and plant/aquarium lamps; thus, identification of Chrysopa spp., damsel bugs, and Hemerobius spp. was more reliable for these light sources. Therefore, the use of cool white light or plant/aquarium light to monitor these taxa is encouraged. Moon phases did not significantly affect light trap catches of the beneficial insects studied. Consequently, moon light should not be considered as an important environmental factor when monitoring these taxa.

Trapa natans is an aquatic plant native to the Old World. In the late 1880s this plant was found to be naturalized in the eastern United States where it has become an important weed. To evaluate the potential of biological control to reduce this weed, surveys for natural enemies of Trapa spp. were made in Northeast Asia and Europe. In addition, populations of Trapa japonica in South Korea were monitored for one season to evaluate the occurrence and impact of insect natural enemies. Among the insects found, the leaf beetle Galerucella birmanica was the most common and damaging species in Asia. It can cause complete defoliation of whole populations of plants. Nymphuline pyralid moths were also common and at times damaging. Both the beetle and the moths feed and develop on unrelated plants and so have no potential as biological control agents of T. natans in North America. Two Nanophyes weevils were found in Asia which feed in petiole floats of the leaves. They are thought to be specific to Trapa but were not observed to be damaging. Low level populations of polyphagous Homoptera were common. Chironomid midges were also frequently associated with the plants, but for the most part were filter feeders, not herbivores. The greatest impact on the monitored plants in South Korea was by the leaf beetle G. birmanica which defoliated most of the plants, causing the mats of plants to sink. In Europe, a similar and related insect fauna was found, but none of the insects was very damaging to the plants. One Italian weevil, Bagous rufimanus, feeds within the fruit stems and might be more damaging at higher than observed population levels. Some diseases were seen on some plants in both regions. European populations of T. natans have declined significantly, stimulating conservation efforts. Literature records of Trapa insects from warm areas are presented. These could be of interest if T. natans spreads into warmer areas of North America.

Omphalapion hookeri(Kirby) (Coleoptera: Apionidae) (= Apion hookeriKirby) was released and established in four provinces in western Canada (British Columbia, Alberta, Saskatchewan, and Manitoba) as a biological control agent for scentless chamomile,Matricaria perforataMerat (Asteraceae), a rapidly spreading, introduced, annual weed of disturbed ground. Larvae of this univoltine European weevil feed on developing achenes in the capitula of scentless chamomile. Overall, 74% of releases resulted in establishment; these included both releases of prediapause adults in late summer or fall and postdiapause adults in early summer. In experimental plots in Alberta,O. hookeripersisted for five consecutive growing seasons from an initial release of 38 adults. Populations in these plots showed year-to-year increases of up to 17-fold, and in mass rearing cages net reproductive rates of up to 64-fold were obtained. Up to 17O. hookerideveloped in a single scentless chamomile seed head in the field. In the field plots each individual ofO. hookericompleting development reduced seed production in a head by 11.2 seeds; unattacked heads produced an average of 171 seeds. A host choice test confirmed thatO. hookeriwould not develop in the herbal chamomile,Chamomilla recutita.AdultO. hookeridispersed up to 350 m between emergence and oviposition. Our results suggest thatO. hookerican be established across the scentless chamomile-infested areas of the Canadian prairies and that it has potential for reducing the weed's reproductive output.

During 1993, potted plants of Tamarix ramosissima C. F. Ledebour (saltcedar) from the United States of America and T. gallica L. from France were placed under Tamarix gallica trees at Sete and Vendemian, southern France, and the natural enemies that at- tacked these plants were recorded. The most promis- ing natural enemies found were three species of Psectrosema (Diptera: Cecidomyiidae); Hypophyes pal- lidulus (Gravenhorst), Corimalia tamarisci (Gyllen- hal), and Coniatus tamarisci F. (Coleoptera: Curculioni- dae); Stylosomus prob. tamaricis (Herrich-Schaffer) (Coleoptera: Chrysomelidae); and Agdistis tamaricis (Zeller) (Lepidoptera: Pterophoridae). The host speci- ficity of these insects was studied in a field test during 1994. Of the 11 plant species tested, none of the economi- cally important plants and neither Tamarix aphylla (L.) nor any of the nine genera of plants outside the family Tamaricaceae were attacked. The above men- tioned natural enemies seem to be specific feeders on saltcedar and are recommended as prospective agents for biological control of T. ramosissima in the United States. r 1998 Academic Press

Opuntia strictais an increasing problem in South Africa's premier wildlife reserve, the Kruger National Park, where the weed continues to disperse and has formed many dense, impenetrable thickets, some of which extend over several hectares. Although herbicidal control measures are being used to help control the weed, a biological control program was initiated in 1988 whenCactoblastis cactorumwas introduced into the park. A primary objective in the control ofO. strictais to prevent fruit production by the plants so that long-range dispersal and recruitment of the weed is minimized.Opuntia strictaplants begin to fruit after approximately six years when they reach a size of 28 cladodes.Cactoblastis cactorumhas become well established in the park and has had a striking effect on both the density and average size of theO. strictaplants in both dense and sparse infestations of the weed. The average size of the plants has declined as the damage caused byC. cactorumlarvae has fragmented the large plants; however, simultaneously, the density of plants has escalated as the fragments have taken root and produced new plants. The net effect has been that the few large plants have been replaced by many smaller plants, but this has not resulted in a significant decline in fruit production. Unlike the situation in Australia and elsewhere in the world, the population densities ofC. cactorumhave not reached the levels required for satisfactory control of the weed. While the reasons for this have not yet been determined, ant predation ofC. cactorumeggs, along with baboon predation of larvae, may contribute to the lack of adequate control.

A field experiment on the ability of a Chinese strain of Chilocorus kuwanae (Silvestri) (Coleoptera: Coccinellidae) to suppress densities of euonymus scale ( Unaspis euonymi [Comstock]) (Homoptera: Diaspididae) on Euonymus spp. in southern New England was conducted from 1991 to 1995. Observations were made at three spatial scales: (1) a set of 27 sites, 14 of which received C. kuwanae releases and 13 served as checks, (2) a single apartment complex, with approximately 110 euonymus shrubs dispersed over 32 ha, at which a single release was made, and (3) the statewide Massachusetts residential and commercial landscape as a whole. Chilocorus kuwanae suppressed U. euonymi at 9 of 14 release sites. The beetle failed to establish large populations at three sites, and at two other sites the experiment was ended prematurely by shrub removal by owners. Of 13 check sites, nine were invaded by C. kuwanae over the course of the experiment and the beetle became abundant at three. Of the 10 check sites where C. kuwanae remained absent or rare, scale numbers increased at four locations, decreased at four, and were unchanged at two. At the 32-ha apartment site, C. kuwanae spread to 64% of all euonymus plants within 4 months and the proportion of plants with heavy euonymus scale infestations decreased from 46 to 13% within 1 year. At the statewide (MA) landscape level, by 1994 no significant change had yet occurred in the proportion of plants with heavy euonymus scale infestations.

The effects of flowering plants on the longevity and fecundity of the proovigenic egg parasitoidCopidosoma koehleriBlanchard, an important parasite of potato moth,Phthorimaea operculella(Zeller), were studied in the laboratory and in the field. Laboratory experimentation showed that fecundity was increased in the presence of honey. WhenC. koehlerifemales were deprived of hosts for the first 5 days of their adult lives, neither the total number of eggs laid nor longevity were significantly affected. Longevity was significantly increased when adults were caged on flowering plants of dill, borage, or coriander. Field cage experiments supported these observations with rates of parasitism inP. operculellabeing significantly higher in fed treatments. A second field trial found that rates of parasitism were greater amongP. operculellalarvae recovered from potato plants growing close to a strip of flowers than in larvae 20 m distant. Pest populations and levels of crop damage were, however, increased by proximity of flowering plants. Laboratory studies subsequently quantified the effect of some flowers onP. operculella,finding that buckwheat and coriander were at least equivalent to honey in increasing fecundity and adult longevity. Findings are discussed in relation to the use of flowering plants as a tool in habitat management for pest control. The use of “selective food plants,” which allow only beneficial insects access to nectaries, is proposed as a new strategy.

Isolate ARSEF 3113, of the fungusBeauveria bassiana(Balsamo) Vuillemin, has potential as a control agent in an integrated pest management program in corn for the European corn borer,Ostrinia nubilalis(Hubner), but its impact on beneficial insects must also be considered. This isolate ARSEF 3113 was tested in the field and laboratory for its compatibility with the coccinellid,Coleomegilla maculataDe Geer. Fourth instars ofC. maculatawere exposed by direct contact with a granular formulation ofB. bassianacontaining 1.1 × 108conidia per gram. No mortality ofC. maculatawas observed, nor was the fungus isolated from any of the exposed coccinellids.Coleomegilla maculatapopulations and indigenousB. bassianaon corn plants and in the soil also were monitored in field plots under three tillage systems. Results suggested a spatial and temporal specificity forB. bassiana.WhenC. maculatadensity was highest,B. bassianawas not isolated from corn plant tissues (leaf collar). We concluded that isolate ARSEF 3113 is compatible withC. maculatain managingO. nubilalisin an Iowa corn ecosystem.

During field surveys made in Europe nearly 40 specialized insect species were found and considered as potential biological control agents of leafy spurge and cypress spurge ( Euphorbia esula and Euphorbia cyparissias ). More insect species were found on the most common and the geographically most widespread spurge species and on those occurring in a wide range of habitat types. The insect families most frequently associated with perennial spurges in Europe are the chrysomelids, sesiids, cecidomyids, and anthomyiids. Although the areas surveyed include only the most western parts of the leafy spurge and cypress spurge distribution in the Palearctic, all food niches and habitats of the target weeds were found to be occupied by herbivorous insects. The history of the search for biological control agents of leafy and cypress spurges in Europe is briefly reviewed. The selection of candidate agents during the past 30 years is discussed, and the 22 insect species which have been screened so far are briefly considered. It is concluded that suitable agents were found outside optimal survey areas with regard to ecoclimatic and host-plant matching.

Common ragweed ( Ambrosia artemisiifolia L.) is an important weed in some parts of Europe. After determining that native natural enemies in Croatia had little influence on controlling this weed, we introduced the beetle Zygogramma suturalis F. from the United States and obtained data on its biology and ecology. We released the beetle in the held at three sites near Bjelovar, Zagreb, and Zadar beginning in 1985. Establishment was confirmed at the Zagreb and Zadar sites from releases made in 1988, but field populations of the beetle remained low through the fall of 1991.

The parasitoid Gyranusoidea tebygi Noyes was released in West Africa against the mango mealybug, Rastrococcus invadens Williams, a pest that invaded Africa in the early 1980s. The ability of G. tebygi to control the mango mealybug was assessed in mango trees using paired sleeve cages. In sleeve cages left open to allow parasitoid attack, G. tebygi reduced mealybug levels 2.7-fold within 1.5 host generations, compared to the closed-sleeve treatment. A parasitism index of 34.4% was measured in the open-sleeve treatment. On leaves without sleeves, the parasitism index was a-fold higher, and the mealybug population level was two times lower than that in the open-sleeve treatment. The lower level of the mealybug population on uncaged leaves, compared to the one on leaves protected by open cages, is attributed to higher mortality caused both by parasitism and by abiotic factors such as rain and wind. The potential of G. tebygi to reduce mango mealybug populations is therefore assumed to be higher than the paired sleeve treatments suggest.

A survey of the phytophagous arthropod fauna associated with four closely related species of Lantana (L. camara, L. urticifolia, L. urticoides, and L. hirsuta) was undertaken in Mexico and the southern United States between 1988 and 1992 to find biological control agents for L. camara, a serious weed in Australia and elsewhere. Some 261 phytophagous insect or mite species (and two rust fungi) were found. Records of species collected during three previous entomological surveys were added to produce a more complete data set of 550 phytophagous species collected throughout North America. Twenty-six of these were considered to have host ranges confined to the subfamily Verbenoideae and thus to be prospective or actual biological control agents.

A comparison of the weeds Sida acuta Burm. f. and S. rhombifolia L. (Malvaceae) as hosts to the potential biological control agent Calligrapha pantherina Stal (Coleoptera: Chrysomelidae) was made in laboratory and glasshouse trials to assess whether host nutritional factors can explain the observed differential performance on these two hosts in the field. There were only minor differences in the life history parameters of insects reared on the two hosts. Larval development time was significantly longer and pupal weights were significantly lower on S. acuta. Survivorship, generation time, net reproductive rate, and the intrinsic rate of increase were not significantly different between hosts. Nutritional indices measuring utilization of the hosts by the insect were also not significantly different between hosts. On the basis of host nutritional factors both species are comparable hosts for C. pantherina. Matching the climate of the native range of this insect to Australia indicates that climatic factors may explain the observed distribution of establishment.

Surveys were carried out in Zambia twice yearly from 1986 to 1990, to assess the impact of a biological control campaign against the cassava mealybug (CM), Phenacoccus manihoti Mat.-Ferr., throughout the infested area. From 1984 onward, the exotic parasitoid Epidinocarsis lopezi (De Santis) (Hym., Encyrtidae) and some exotic coccinellid predators were released on 54 occasions along the spreading front of CM infestation. E. lopezi established in every release site, spread, and covered the entire infested area, but the exotic coccinellids did not establish. Between 1986 and 1990, CM populations declined on average 5.8 times. In a multiple regression analysis involving meteorological, agronomic, plant, and entomological variables, from a total of 4804 cassava fields, nine variables had a significant influence on the CM population density, which in turn was the main factor influencing tip damage scores. The duration of E. lopezi′s presence in an area was the most important factor: in the year the CM was recorded for the first time in a particular district, more than 20% of all cassava fields had an average of 10 or more CM/tip (a few having as many as 1000). This percentage was gradually reduced to 0% in Year 5. The condition of the plant, its age, rainfall, and water retention capacity of the soil were also important. Where CM populations were lower, damage by the cassava green mite, Mononychellus tanajoa (Bondar) (Acari, Tetranychidae), appeared more severe. The frequency of ants increased with the CM population density. In conclusion, biological control of the CM in Zambia was successful.

Variation in resistance to thistle-head insects was studied in plants of Centaurea solstitialis L. (yellow starthistle) derived from Nearctic and Palearctic populations and grown in common gardens near Rome, Italy. Significant variation was found in the percentage of insect-damaged flowerheads among plant populations, with aggregate rates of herbivory higher on plants of the local (Italian) population. Two tephritid flies, Acanthiophilus helianthi (Rossi) and Chaetorellia succinia (Costa), accounted for most of the damage to all populations. In addition, more species of insects exploited the capitula of Italian plants (eight vs three to six species for the other populations). That only Italian plants were suitable host plants for Urophora jaculata Rondani suggests a host-plant resistance factor was responsible for the failure of this tephritid fly to become established on yellow starthistle in California. These results indicate that all populations of yellow starthistle are not equally susceptible to herbivory by thistle-head insects. On the other hand, adults of two potential biocontrol agents, U. quadrifasciata quadrifasciata (Meigen) and Terellia uncinata White, emerged from American plants; thus, there is reason to believe these tephritid flies would establish on Nearctic populations. Variation in resistance among plant populations was not related to differences in plant size. The overall results are consistent with the findings of other ecologists that noncrop plant species vary significantly in their resistance to individual herbivore species and to groups of insect herbivores. The results also point to the usefulness of the open field approach in host-specificity determination of insects for biological control of weeds.

A survey for natural enemies of Thrips palmi Karny was conducted in its native habitat, Thailand, in 1987 and 1988 to develop a classical biological control program for this exotic pest of vegetables in Japan. One egg parasitoid, one larval parasitoid, and six larval predators were found. Of these eight natural enemies, the eulophid larval parasitoid Ceranisus menes (Walker) was the most effective, based on a study in a test plot of eggplant in Bangkok and an extensive survey of eggplant fields in several districts of Thailand in 1988. Parasitism by C. menes was usually limited to home gardens which were not sprayed with insecticides, suggesting a detrimental effect of insecticide applications on the parasitoid. The anthocorid larval predator Bilia sp. was the second most effective natural enemy. Problems associated with the introduction of these two promising biological control agents in relation to the occurrence of native natural enemies of T. palmi in Japan are discussed.

The response of the seven-spotted lady beetle, Coccinella septempunctata (L.) (Coleoptera: Coccinellidae), the parenthesis lady beetle, Hippodamia parenthesis (Say), (Coleoptera: Coccinellidae), and the green lacewing, Chrysoperla carnea (Stephens), (Neuroptera: Chrysopidae) to seven colors was evaluated in the field using sticky panels. C. septempunctata exhibited a strong positive response to yellow. C. carnea showed a preference for yellow, green, and red. H. parenthesis did not exhibit strong visual orientation to any color. Programs aimed at monitoring these predators should consider their visual responses to colors in designing monitoring systems.

Parasitoids of an undescribed species of apple leafminer, Phyllonorycter nr. elmaella , were studied to determine their relative and seasonal abundance. Thirty-six percent of all parasitoids were Sympiesis marylandensis Girault, 48% were Pnigalio flavipes (Ashmead), 7% were Zagrammosoma mirum Girault, >1% were Pholetesor ornigis (Weed), and the remaining 10% were other eulophids. Percentage parasitism varied greatly between leafminer generations and between locations during the apple growing season. Cannibalism caused 45% of the mortality during the first generation and 10 and 14% during the third and fourth leafminer generations, respectively. Pesticide residues targeted for control of codling moth, Cydia pomonella (L.), caused 90–100% mortality of the two most abundant parasitoids 24 h after application. S. marylandensis was more susceptible than P. flavipes to azinphosmethyl residues.

While the accidental introduction of insect pests is becoming increasingly common due to intense and rapid commercial exchanges, the incidence of accidental introduction of their parasitoids seems to be much less frequent or is overlooked. The case reported here, for a tachinid Phasiinae, is both fortuitous and fortunate since the parasitoid has been carried from the New World by a pest that is already present in the new country, Italy, where there are virtually no competitors. Establishment and specificity of the parasitoid was confirmed by the first follow-up studies immediately after its discovery.

Habitat manipulation has long been used as strategy to enhance beneficial insects in agroecosystems. Non-crop weed strips have the potential of supplying food resources to natural enemies, even when pest densities are low. However, in tropical agroecosystems there is a paucity of information pertaining to the resources provided by non-crop weeds and their interactions with natural enemies. In this study we evaluated (a) whether weeds within chili pepper fields affect the diversity and abundance of aphidophagous species; (b) whether there are direct interactions between weeds and aphidophagous arthropods; and (c) the importance of weed floral resources for survival of a native and exotic coccinellid in chili pepper agroecosystems. In the field, aphidophagous arthropods were dominated by Coccinellidae, Syrphidae, Anthocoridae, Neuroptera and Araneae, and these natural enemies were readily observed preying on aphids, feeding on flowers or extrafloral nectaries, and using plant structures for oviposition and/or protection. Survival of native Cycloneda sanguinea (Coleoptera: Coccinellidae) differed between plant species, with significantly greater survival on Ageratum conyzoides and Bidens pilosa. However, no evidence was gathered to suggest that weed floral resources provided any nutritional benefit to the exotic Harmonia axyridis (Coleoptera: Coccinellidae). This research has provided evidence that naturally growing weeds in chili pepper agroecosystems can affect aphid natural enemy abundance and survival, highlighting the need for further research to fully characterize the structure and function of plant resources in these and other tropical agroecosystems.