James R. Hagler

Foraging behavior and prey interactions by a guild of predators on various lifestages of Bemisia tabaci.

Abstract The sweetpotato whitefly, Bemisia tabaci (Gennadius) is fed on by a wide variety of generalist predators, but there is little information on these predator-prey interactions. A laboratory investigation was conducted to quantify the foraging behavior of the adults of five common whitefly predators presented with a surfeit of whitefly eggs, nymphs, and adults. The beetles, Hippodamia convergens Guérin-Méneville and Collops vittatus (Say) fed mostly on whitefly eggs, but readily and rapidly preyed on all of the whitefly lifestages. The true bugs, Geocoris punctipes (Say) and Orius tristicolor (Say) preyed almost exclusively on adult whiteflies, while Lygus hesperus Knight preyed almost exclusively on nymphs. The true bugs had much longer prey handling times than the beetles and spent much more of their time feeding (35–42%) than the beetles (6–7%). These results indicate that generalist predators vary significantly in their interaction with this host, and that foraging behavior should be considered during development of a predator-based biological control program for B. tabaci. ELISA enzyme-linked immunosorbent assay

Identifying the predator complex of Homalodisca vitripennis (Hemiptera: Cicadellidae): a comparative study of the efficacy of an ELISA and PCR gut content assay

A growing number of ecologists are using molecular gut content assays to qualitatively measure predation. The two most popular gut content assays are immunoassays employing pest-specific monoclonal antibodies (mAb) and polymerase chain reaction (PCR) assays employing pest-specific DNA. Here, we present results from the first study to simultaneously use both methods to identify predators of the glassy winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). A total of 1,229 arthropod predators, representing 30 taxa, were collected from urban landscapes in central California and assayed first by means of enzyme-linked immunosorbent assay (ELISA) using a GWSS egg-specific mAb and then by PCR using a GWSS-specific DNA marker that amplifies a 197-base pair fragment of its cytochrome oxidase gene (subunit I). The gut content analyses revealed that GWSS remains were present in 15.5% of the predators examined, with 18% of the spiders and 11% of the insect predators testing positive. Common spider predators included members of the Salticidae, Clubionidae, Anyphaenidae, Miturgidae, and Corinnidae families. Common insect predators included lacewings (Neuroptera: Chrysopidae), praying mantis (Mantodea: Mantidae), ants (Hymenoptera: Formicidae), assassin bugs (Hemiptera: Reduviidae), and damsel bugs (Hemiptera: Nabidae). Comparison of the two assays indicated that they were not equally effective at detecting GWSS remains in predator guts. The advantages of combining the attributes of both types of assays to more precisely assess field predation and the pros and cons of each assay for mass-screening predators are discussed.

An Inexpensive Immunomarking Technique for Studying Movement Patterns of Naturally Occurring Insect Populations

Abstract An immunomarking system useful for determining insect movement patterns was developed that allows the marking of naturally occurring populations of insects within large areas with inexpensive and readily available proteins that can be applied using standard spray equipment. Enzyme-linked immunosorbent assay (ELISA) protocols were developed to detect chicken egg albumin (as egg whites), bovine casein (as cows’ milk), and soy protein (as soy milk) at levels ≤30 ppb. Field applications showed that all of the proteins were stable and detectable at high levels on apple leaves at least 19 d after application. When adult pear psylla (Cacopsylla pyricola Foerster, Homoptera: Psyllidae) walked across apple leaves with field-aged residues of the marker proteins plus either Sylgard 309, EDTA, or both, they acquired the mark over the 19-d test period an average of 78.9, 19.4, and 2.1% of the time for egg whites, milk, and soy milk, respectively. Two field applications of the three markers were applied to an apple orchard during the first generation flight of codling moth (Cydia pomonella L., Lepidoptera: Tortricidae). We found that 46.5% of moths captured within a 2.8-ha area (including 1.6-ha surrounding the treated areas) tested positive for at least one of the three proteins. The marker systems developed cost between

Improved Conservation of Natural Enemies with Selective Management Systems for Bemisia tabaci (Homoptera: Aleyrodidae) in Cotton*

0.12 and

Comparative Dispersal of Homalodisca coagulata and Homalodisca liturata (Homoptera: Cicadellidae)

0.26liter versus older immunomarkers (using purified vertebrate IgG) that cost roughly

Use of a gut content ELISA to detect whitefly predator feeding activity after field exposure to different insecticide treatments

500/liter.

Distribution and activity of Drosophila suzukii in cultivated raspberry and surrounding vegetation

A large-scale study was conducted in 1996 to evaluate and demonstrate strategies for pest management of Bemisia tabaci (Gennadius) in cotton involving different insecticide regimes, application methods, and action thresholds. Here we examined the effects of the various management systems on the abundance and activity of native natural enemies. Population densities of 18 out of 20 taxa of arthropod predators were significantly higher in regimes initiated with the insect growth regulators (IGRs) buprofezin (chitin inhibitor) or pyriproxyfen (juvenile hormone analog) compared with a regime dependent on a rotation of conventional, broad-spectrum insecticides. There were no differences in predator density between the two IGR regimes, and generally no effects due to application method or action threshold level. Predator to prey ratios were significantly higher in regimes utilizing the two IGRs compared with the conventional regime, but were unaffected by application method or threshold level. Rates of parasitism by Eretmocerus eremicus Rose and Zolnerowich and Encarsia meritoria Gahan were higher in the IGR regimes compared with the conventional regime, but were unaffected by insecticide application method, or the action threshold used to initiate applications of the IGRs. Results demonstrate the selective action of these two IGRs and suggest that their use may enhance opportunities for conservation biological control in cotton systems affected by B. tabaci, especially relative to conventional insecticide alternatives.

Parasitoid Mark-Release-Recapture Techniques-- II. Development and Application of a Protein Marking Technique for Eretmocerus spp., Parasitoids of Bemisia argentifolii

Abstract California’s viticulture and ornamental industries have suffered significant losses since the introduction of Homalodisca coagulata (Say), an important vector of the Pierce’s disease bacterium. A better understanding of the factors that influence the dispersal of H. coagulata, as well as other native sharpshooters could enhance our ability to institute areawide management programs. Studies were conducted to establish the validity of an immunoglobulin G (IgG) protein marker for sharpshooter dispersal studies, to compare the dispersal of H. coagulata with that of a native sharpshooter Homalodisca liturata Ball, and to develop a better understanding of the factors that influence their dispersal. Field trials showed that the marker remained detectable for at least 19 d and did not affect sharpshooter survival. Four concentrations (0.04, 0.2, 1, and 5 mg/ml) and two different IgG markers (chicken and rabbit) were effective for marking sharpshooters. In mass-mark-recapture studies, ≈95% of the marked insects flew during the releases and the timing of flight initiation was similar for H. coagulata and H. liturata. Mean wind speeds >3 m s−1 were associated with a decline in flight initiation for both species. Most sharpshooters were trapped at heights below 4.2 m, and based on sex ratio comparisons, traps were equally attractive to males and females. Regression analyses of recapture data and a diffusion model were used to assess and compare sharpshooter dispersal. The majority (95%) of H. coagulata and H. liturata were recaptured within 90 and 155 m of the release site, respectively.

Development of molecular diagnostic markers for sharpshooters Homalodisca coagulata and Homalodisca liturata for use in predator gut content examinations

Abstract A 2-year commercial-scale study was conducted to qualitatively evaluate the effect of different insecticide treatment regimes on the predator complex attacking Bemisia tabaci (Gennadius) in cotton. In 1996 three insecticide regimes were compared: a rotation of conventional broad-spectrum insecticides or one of two different regimes based on the initial use of the insect growth regulators (IGRs), buprofezin and pyriproxyfen. In 1997 the same three regimes plus an untreated control were compared; split-plots were sprayed once for Lygus hesperus Knight control using a broad-spectrum insecticide. Relative feeding activity for each predator species was compared between treatment regimes by analyzing the gut contents of predators for the presence of whitefly remains using a whitefly-specific enzyme-linked immunosorbent assay (ELISA). The ELISA results were combined with predator density data to obtain a qualitative pesticide impact index for each predator group. In total, we analyzed the gut contents of 32 262 field-collected predators, representing nine different taxa. Of these, Pseudatomocelis seriatus (Reuter), Spanagonicus albofasciatus (Reuter), and spiders consisting primarily of Misumenops celer (Hentz) are shown to be whitefly predators for the first time. Predator populations were usually reduced in plots that received applications of broad-spectrum insecticides for B. tabaci and L. hesperus control, but there were few treatment differences in the proportions of predators containing whitefly remains in their guts. However, the feeding activity of certain predator species in fields sprayed with broad spectrum insecticides was significantly reduced compared with those in IGR-based and control treatments. Overall, insecticide regimes using IGRs were less lethal to the whitefly predator complex than regimes consisting of only conventional, broad-spectrum insecticides, but differences in predator feeding activity on whitefly between the various insecticide treatment regimes were minimal.

The flow of incoming nectar through a honey bee (Apis mellifera L.) colony as revealed by a protein marker.

Spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), may utilize wild ‘Himalaya’ blackberry (HB) Rubus armeniacus Focke or other non‐crop plants as refugia and possibly exploit adjacent field margins before colonizing cultivated fruiting crops. Studies were conducted to determine the role of field margins containing HB and their effect on D. suzukii activity, density and distribution in an adjacent commercial red raspberry crop. One‐ha plots adjacent to field margins containing HB or known non‐host (NH) grass crops were established in 2011 and 2012 and replicated three times. Each plot contained two transects with monitoring traps for D. suzukii in the field margin (0 m) and spaced approximately 10 (crop boundary), 40, 70 and 100 m into the adjacent crop (n = 10 traps/plot). Field margin vegetation was treated with a 10% chicken egg white mark solution weekly from pre‐harvest until the end of harvest using a cannon sprayer. Adult D. suzukii were collected from traps weekly and analysed for the presence of the egg white mark using an egg white‐specific enzyme‐linked immunosorbent assay (ELISA). During both years, marked flies and total flies were captured in higher numbers in HB field margins, whereas virtually no flies were captured in field margins containing no known alternative host. Similarly, more flies were captured in the crop near HB than near NH. Spatial Analysis by Distance IndicEs (SADIE) and mean D. suzukii trap captures additionally displayed significantly higher fly densities in the raspberry field near HB than near NH. These results suggest that HB may contribute to elevated D. suzukii populations and pest pressure in comparison with field margins containing no known alternate host vegetation for D. suzukii. Having closely adjacent non‐crop alternate host landscapes may result in increased D. suzukii pest pressure.