Douglas B. Walsh

Drosophila suzukii (Diptera: Drosophilidae): Invasive Pest of Ripening Soft Fruit Expanding its Geographic Range and Damage Potential

Spotted wing drosophila, Drosophila suzukii Matsumura, a native of eastern and southeastern Asia, is a pest of small and stone fruits. First detected in California in 2008, the insect is now found across the Pacific Coast states. Its penchant for attacking healthy, ripening fruit (as opposed to overripe and rotting fruit favored by other so-called “vinegar flies”) makes it a potential economic threat to a host of soft- and thin-skinned fruit crops including cherry, raspberry, blackberry, blueberry, strawberry, peach, plums, pluots, nectarines, juice grape, table grape, and wine grape. Coordinated research projects to determine host preference, seasonal phenology, biology, and management options are taking place among entomologists in Washington, Oregon, and California. A description of the pest and initial findings on its biology, life history, known and expected geographic range, management and monitoring techniques, and economic considerations are presented and discussed.

Laboratory survival of Drosophila suzukii under simulated winter conditions of the Pacific Northwest and seasonal field trapping in five primary regions of small and stone fruit production in the United States.

BACKGROUND Drosophila suzukii was first found in Oregon in August 2009. The threat of this pest to regional small and stone fruit production industries led to investigations on its overwintering capabilities in fruit-growing regions in the Pacific Northwest. Knowledge of its cold tolerance will help in the development of computer models to forecast seasonal population growth and decline. RESULTS Of 1500 adults or pupae, 22 (1.4%) individuals survived the 84 day experimental chilling period. Most (86%) of the survivors were subjected to 10 °C temperature treatments. Survival decreased significantly at lower temperature treatments. Freezing temporarily increased the mortality rate but did not significantly affect overall mortality over the trial period. Flies that emerged from pupae are estimated to survive for up to 103-105 days at 10 °C and for shorter periods at lower temperatures. Field trapping in five fruit production areas has demonstrated overwintering survival in California and Oregon, but lower survival is predicted in Eastern Washington and Michigan. CONCLUSION The experiments reported here indicate that long-term survival of D. suzukii is unlikely at temperatures below 10 °C. Field data from five climatic regions indicated extended low initial D. suzukii field presence in 2010 in all regions except California, where field presence was recorded earlier.

Multistate Comparison of Attractants for Monitoring Drosophila suzukii (Diptera: Drosophilidae) in Blueberries and Caneberries

ABSTRACT Drosophila suzukii Matsumara, also referred to as the spotted wing drosophila, has recently expanded its global range with significant consequences for its primary host crops: blueberries, blackberries, raspberries, cherries, and strawberries. D. suzukii populations can increase quickly, and their infestation is difficult to predict and prevent. The development of effective tools to detect D. suzukii presence in new areas, to time the beginning of activity within a crop, to track seasonal activity patterns, and to gauge the effectiveness of management efforts has been a key research goal. We compared the efficiency, selectivity, and relationship to fruit infestation of a range of commonly used homemade baits and a synthetic formulated lure across a wide range of environments in 10 locations throughout the United States. Several homemade baits were more efficient than apple cider vinegar, a commonly used standard, and a commercially formulated lure was, in some configurations and environments, comparable with the most effective homemade attractant as well as potentially more selective. All alternative attractants also captured flies between 1 and 2 wk earlier than apple cider vinegar, and detected the presence of D. suzukii prior to the development of fruit infestation. Over half the Drosophila spp. flies captured in traps baited with any of the attractants were not D. suzukii, which may complicate their adoption by nonexpert users. The alternative D. suzukii attractants tested are improvement on apple cider vinegar and may be useful in the development of future synthetic lures.

Development of a Multiplex PCR for Identification of Vineyard Mealybugs

ABSTRACT A simple molecular tool was developed and tested to identify seven mealybug species found in North American vineyards: Pseudococcus maritimus Ehrhorn, Pseudococcus viburni (Signoret), Pseudococcus longispinus (Targioni-Tozzeti), Pseudococcus calceolariae (Maskell), Planococcus ficus (Signoret), Planococcus citri (Risso), and Ferrisia gilli Gullan. The developed multiplex PCR is based on the mitochondrial cytochrome c oxidase subunit one gene. In tests, this single-step multiplex PCR correctly identified 95 of 95 mealybug samples, representing all seven species and collected from diverse geographic regions. To test the sensitivity, single specimen samples with different Pl. ficus developmental stages (egg to adult female and adult male) were processed PCR and the resulting output provided consistent positive identification. To test the utility of this protocol for adult males caught in sex baited pheromone traps, Pl. ficus adult males were placed in pheromone traps, aged at a constant temperature of 26 ± 2°C, and processed with the multiplex each day thereafter for 8 d. Results showed consistent positive identification for up to 6 d (range, 6–8 d). Results are discussed with respect to the usefulness of this molecular tool for the identification of mealybugs in pest management programs and biosecurity of invasive mealybugs.

Insecticide Resistance and Management Strategies in Urban Ecosystems

The increased urbanization of a growing global population makes imperative the development of sustainable integrated pest management (IPM) strategies for urban pest control. This emphasizes pests that are closely associated with the health and wellbeing of humans and domesticated animals. Concurrently there are regulatory requirements enforced to minimize inadvertent exposures to insecticides in the urban environment. Development of insecticide resistance management (IRM) strategies in urban ecosystems involves understanding the status and mechanisms of insecticide resistance and reducing insecticide selection pressure by combining multiple chemical and non-chemical approaches. In this review, we will focus on the commonly used insecticides and molecular and physiological mechanisms underlying insecticide resistance in six major urban insect pests: house fly, German cockroach, mosquitoes, red flour beetle, bed bugs and head louse. We will also discuss several strategies that may prove promising for future urban IPM programs.

Transcriptome-Based Identification of ABC Transporters in the Western Tarnished Plant Bug Lygus hesperus

ATP-binding cassette (ABC) transporters are a large superfamily of proteins that mediate diverse physiological functions by coupling ATP hydrolysis with substrate transport across lipid membranes. In insects, these proteins play roles in metabolism, development, eye pigmentation, and xenobiotic clearance. While ABC transporters have been extensively studied in vertebrates, less is known concerning this superfamily in insects, particularly hemipteran pests. We used RNA-Seq transcriptome sequencing to identify 65 putative ABC transporter sequences (including 36 full-length sequences) from the eight ABC subfamilies in the western tarnished plant bug (Lygus hesperus), a polyphagous agricultural pest. Phylogenetic analyses revealed clear orthologous relationships with ABC transporters linked to insecticide/xenobiotic clearance and indicated lineage specific expansion of the L. hesperus ABCG and ABCH subfamilies. The transcriptional profile of 13 LhABCs representative of the ABCA, ABCB, ABCC, ABCG, and ABCH subfamilies was examined across L. hesperus development and within sex-specific adult tissues. All of the transcripts were amplified from both reproductively immature and mature adults and all but LhABCA8 were expressed to some degree in eggs. Expression of LhABCA8 was spatially localized to the testis and temporally timed with male reproductive development, suggesting a potential role in sexual maturation and/or spermatozoa protection. Elevated expression of LhABCC5 in Malpighian tubules suggests a possible role in xenobiotic clearance. Our results provide the first transcriptome-wide analysis of ABC transporters in an agriculturally important hemipteran pest and, because ABC transporters are known to be important mediators of insecticidal resistance, will provide the basis for future biochemical and toxicological studies on the role of this protein family in insecticide resistance in Lygus species.

Integrating arthropod herbivory and reduced herbicide use for weed management

Abstract Few studies have examined the combined effect of herbicide-induced stress and arthropod herbivory to reduce weed fitness. The purpose of this study was to quantify the effect of arthropod herbivory on the herbicide dose–response of a perennial weed. Fluroxypyr dose–response bioassays using volunteer potato were conducted in the presence and absence of Colorado potato beetle (CPB) herbivory. Logistic model parameter estimates for leaf area, shoot biomass, tuber number, and tuber biomass were often lower with herbivory, compared with no herbivory. Greater variance of parameter estimates within herbivory plots was attributed largely to differential feeding because CPB density was not manipulated in the field. Results from short-season field studies (1,000 growing degree days [GDD] after postemergence [POST] herbicide application) indicated that herbivory had the most effect on potato during a period that coincided with high CPB density and optimal temperatures for CPB development. Season-long bioassays (> 3,100 GDD after POST) revealed that addition of herbivory reduced herbicide use 65 to > 85%, compared with the dose needed to achieve the same reduction in tuber production in the absence of herbivory. Integrated weed management systems targeting volunteer potato are more effective when fluroxypyr applications are made before periods of high herbivory. Moreover, this article describes an experimental approach contributing to optimization of combined effects of arthropod herbivory and reduced herbicide doses. Nomenclature: Fluroxypyr; volunteer potato, Solanum tuberosum L.

Analysis of Permethrin (Cis- and Trans-Isomers) and Esfenvalerate on Almond Twigs and Effects of Residues on the Predator Mite Galendromus occidentalis (Acari: Phytoseiidae)

Abstract A gas chromatograph-electron capture detection method for analysis of permethrin (cis- and trans-isomers) and esfenvalerate on the surface of almond twigs is described. Permethrin and esfenvalerate were extracted from the substrate with a hexane sonication, Florisil solid phase extraction cleanup, and quantification by gas-liquid chromatography with electron capture detector with a megabore capillary column. The mean recoveries for all three analytes were 87% with a coefficient of variation <13% at fortification levels ranging from 50 to 1,000 ng for each analyte. The limit of detection was 14, 13, and 4 ng for cis-permethrin, trans-permethrin and esfenvalerate respectively for almond twigs. Field collected twig samples taken 7 mo after pesticide application were found to contain measurable bark surface residues. Bioassays using those twigs indicated significant mortality to the beneficial mite, Galendromus occidentalis Nesbitt.

Impact of sustained deficit irrigation on spearmint (Mentha spicata L.) biomass production, oil yield, and oil quality

Crop response to deficit irrigation is an important consideration for establishing irrigation management strategies when water supplies are limited. This study evaluated the response of native spearmint to water deficits applied using overhead sprinklers in eastern Washington, US. Five levels of irrigation were applied ranging from full irrigation (100%) to 5% of weekly averaged full crop water needs. Soil water monitoring with soil water balance was used to estimate soil water deficits for irrigation scheduling and soil water use. Mint oil yields, oil components, dry matter production, and the water-use efficiency of the spearmint were assessed. There was significant reduction in fresh mint hay (harvested biomass) yield with increasing water deficit. However, spearmint oil yields remained generally uniform across irrigation treatments at the first cutting but decreased at the driest plots during the second harvest due to a loss of plant stand. The wet harvest index and water-use efficiency improved significantly for both harvests with increasing water deficit. Hay yield, oil yield, wet harvest index, and water-use efficiency are pooled across sides and replicate blocks to provide trends with changes in maximum evapotranspiration. The three major monoterpenes show changes suggesting less mature oil yields. The study demonstrates the feasibility of sustaining native spearmint yields under managed deficit irrigations for deficits not lower than 0.5 ETc.

An Endemic Population of Western Poplar Clearwing Moths (Lepidoptera: Sesiidae) Invades a Monoculture of Hybrid Poplar

Western poplar clearwing, Paranthrene robiniae (Hy. Edwards) (Lepidoptera: Sesiidae), is endemic in Pacific Northwest riparian habitats at low population densities. These moths have colonized commercial hybrid poplar (Populus spp.) plantings. Moth populations increased rapidly and became a major pest. Trap catches of male moths in mid-season surveys increased 190-fold from 95 in 2001 to >18,500 in 2002 across 6597 ha of poplars monitored. The outbreak of western poplar clearwings was widespread in 2002. Pheromone-baited traps placed one trap per 81.75 ha over 13,274 ha of commercial poplars captured >108,000 male moths in 2002. Damage to commercial poplars included girdling of saplings and burrows in limbs and trunks of trees. Repeated applications of chlorpyrifos failed to reduce the abundance of moths in 2002. Two management strategies over two separate plantations of approximately 6500 ha each were contrasted. Future control strategies recommend a halt to the use of contact insecticides that target adult moths. Short-term (3-5 yr) control should involve a pheromone-based mating disruption strategy followed eventually by selection of a clone that is less susceptible to P. robiniae attack.