Frank G. Zalom

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.

Spotted wing drosophila infestation of California strawberries and raspberries: economic analysis of potential revenue losses and control costs

BACKGROUND Economic costs of spotted wing drosophila (SWD) include yield and associated revenue losses, labor and material costs for monitoring and management and revenue losses due to the closure of export markets should fruit from SWD-infested regions be banned by trading partners. This analysis focuses on two types of loss in the California raspberry and strawberry industries: yield losses in the absence of management, and insecticide material costs on a per treatment basis. It computes the cost of a specific management program for raspberries in Californias Central Coast region. RESULTS Insecticide material and application costs per treatment and the cost of the management program are small relative to the yield losses in the absence of management that are observed by growers, researchers and others in initial infestations. CONCLUSION It is difficult to evaluate precisely the share of pest management program costs due to SWD because insecticides are sometimes used to manage multiple pests, and because labor-intensive field sanitation efforts to control SWD are recommended practices already. Given these considerations, this analysis finds that the benefits to SWD management well outweigh the costs examined here. Evaluating the efficacy of managing SWD is essential in assessing the risks that SWD poses and the benefits of pest management programs.

Host-plant green-leaf volatiles synergize the synthetic sex pheromones of the corn earworm and codling moth (Lepidoptera).

SummaryThe capture of adult male moths in female sex pheromone traps of two key agricultural pests, the corn earworm (Helicoverpa zea) and the codling moth (Cydia pomonella), is enhanced or synergized by a certain group of host-plant volatiles, the “green-leaf volatiles” (GLVs). Since female adults of both species call and release their sex pheromones while perched upon the leaves of their host-plants, the volatile constituents from the leaves of a number of host-plants were compared. Sex pheromone traps containing one of the prominent leaf volatiles of certainH. zea hosts, (Z)-3-hexenyl acetate, not only significantly increased the capture ofH. zea males but were preferred over traps baited only with sex pheromone. Similarly, traps baited with synthetic sex pheromome ofC. pomonella plus a blend of GLVs captured significantly more males than traps baited only with sex pheromone. Since male moths are not captured in traps baited only with these GLVs, it appears that these GLVs act as pheromone synergists which increase or enhance the attraction or arrestment of male moths in pheromone traps.

Agronomic, economic, and environmental comparison of pest management in conventional and alternative tomato and corn systems in northern California

The effectiveness, economic efficiency, and environmental impact of pest management practices was compared in conventional, low-input, and organic processing tomato and field corn systems in northern California. Pests, including arthropods, weeds, pathogens, and nematodes, were monitored over an 8-year period. Although both crops responded agronomically to the production-system treatments, arthropods, pathogens, and nematodes were found to play a relatively small role in influencing yields. In contrast, weed abundance was negatively correlated with tomato and corn yields and appeared to partially account for lower yields in the alternative systems compared to the conventional systems. Lower pesticide use in the organic and low-input systems resulted in considerably less potential environmental impact but the economic feasibility of reducing pesticide use differed dramatically between the two crops. The performances of the organic and low-input systems indicate that pesticide use could be reduced by 50% or more in corn with little or no yield reduction. Furthermore, the substitution of mechanical cultivation for herbicide applications in corn could reduce pest management costs. By contrast, pesticide reductions in tomato would be economically costly due to the dependence on hand hoeing as a substitution for herbicides. Based on the performance of the low-input and organic tomato systems, a 50% pesticide reduction would increase average pest management costs by 50%.

Associations of Yeasts with Spotted-Wing Drosophila (Drosophila suzukii; Diptera: Drosophilidae) in Cherries and Raspberries

ABSTRACT A rich history of investigation documents various Drosophila-yeast mutualisms, suggesting that Drosophila suzukii similarly has an association with a specific yeast species or community. To discover candidate yeast species, yeasts were isolated from larval frass, adult midguts, and fruit hosts of D. suzukii. Terminal restriction fragment length polymorphism (TRFLP) technology and decimal dilution plating were used to identify and determine the relative abundance of yeast species present in fruit juice samples that were either infested with D. suzukii or not infested. Yeasts were less abundant in uninfested than infested samples. A total of 126 independent yeast isolates were cultivated from frass, midguts, and fruit hosts of D. suzukii, representing 28 species of yeasts, with Hanseniaspora uvarum predominating. This suggests an association between D. suzukii and H. uvarum that could be utilized for pest management of the highly pestiferous D. suzukii.

Evaluation of Monitoring Traps for Drosophila suzukii (Diptera: Drosophilidae) in North America

ABSTRACT Drosophila suzukii Matsumura (Diptera: Drosophilidae), a recent invasive pest of small and stone fruits, has been detected in more than half of the U.S. states, and in Canada, Mexico, and Europe. Upon discovery, several different trap designs were recommended for monitoring. This study compared the trap designs across seven states/provinces in North America and nine crop types. Between May and November 2011, we compared a clear cup with 10 side holes (clear); a commercial trap with two side holes (commercial); a Rubbermaid container with mesh lid and rain tent (Haviland), and with 10 side holes and no tent (modified Haviland); a red cup with 10 side holes (red); and a white container with mesh lid and rain tent (Van Steenwyk). Although fly catches among traps varied per site, overall, the Haviland trap caught the most D. suzukii, followed by the red, Van Steenwyk, and clear trap. The modified Haviland and commercial trap had low captures. Among five crop types in Oregon, a clear cup with mesh sides (Dreves) also was tested and caught the most flies. Traps with greater entry areas, found in mesh traps, caught more flies than traps with smaller entry areas. In terms of sensitivity and selectivity, traps that caught more flies likewise caught flies earlier, and all traps caught 26–31% D. suzukii out of the total Drosophila captured. Future trap improvements should incorporate more entry points and focus on selective baits to improve efficiency and selectivity with regard to the seasonal behavior of D. suzukii.

Sex Attractant Pheromone of the Red-Shouldered Stink Bug Thyanta pallidovirens: A Pheromone Blend with Multiple Redundant Components

The male-produced sex pheromone of the red-shouldered stink bug, Thyanta pallidovirens (Stål) (Hemiptera: Pentatomidae) consists of a blend of methyl (E2,Z4,Z6)-decatrienoate (E2,Z4,Z6–10:COOMe), and the sesquiterpenes (+)α-curcumene, (−)-zingiberene, and (−) -β-sesquiphellandrene. In laboratory bioassays, sexually mature males attracted sexually mature females but not males, and females did not attract either sex. Extracts of volatiles collected from sexually mature males contained compounds not present in extracts from females or sexually immature males, and male-produced extract was attractive to females. Biological activity was lost when the extract was fractionated, indicating that the pheromone consisted of at least two components having different chemical properties. Individually, pheromone components were not attractive to females, but E2,Z4,Z6–10:COOMe in combination with at least one of the three male-produced sesquiterpenes was attractive. The presence of more than one sesquiterpene in the blend did not increase attraction, indicating redundancy in the pheromone signal. Male extract was as attractive as a blend reconstructed from synthesized compounds, indicating all biologically active components had been identified. In bioassays conducted at dusk in a 1- × 1- × 1-m screen field cage, females were attracted to synthetic pheromone lures. In field trials, adult female T. pallidovirens were attracted to pheromone-baited traps in relatively low numbers. The profile of volatiles released by sexually mature males of a congeneric species, Thyanta accerra custator McAtee, was remarkably similar to that of male T. pallidovirens, with the exception that the former species produced (E)-2-decenal, a compound that was not found in T. pallidovirens extracts.

Analysis of olive fly invasion in California based on microsatellite markers

The olive fruit fly, Bactrocera oleae, is the main pest of the olive fruit and its expansion is exclusively restricted to the cultivation zone of the olive tree. Even though olive production has a century-old history in California, the olive fly was first detected in the Los Angeles area in 1998. Within 5 years of the first observation, the insect was reported from all olive cultivation areas of the state. Field-collected flies from five locations in California and another from Israel were analyzed on the basis of microsatellite polymorphisms in 10 microsatellite loci. These results were integrated with those of a previous study of olive fly populations around the European part of the Mediterranean basin. The analysis pointed to the eastern part of the Mediterranean as the putative source of the observed invasion. Moreover, samples from California were quite different from Mediterranean samples implying the participation of phenomena such as genetic drift during the invasion and expansion of the olive fly in California.

Olive Fruit Fly (Diptera: Tephritidae) Ovipositional Preference and Larval Performance in Several Commercially Important Olive Varieties in California

Abstract The olive fruit fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae), is an invasive pest of olives (Olea spp.) in the United States. The objectives of this study were to determine whether B. oleae exhibits ovipositional preference under California field conditions similar to that demonstrated in European populations and whether the resulting larvae fare better in preferred varieties. Female B. oleae exhibited strong ovipositional preference for certain varieties of the domesticated olive, Olea europaea L, and the resulting larvae performed better by some measures in preferred varieties than in lesser preferred varieties. Ovipositional preference was observed in the field from 2003 to 2005, and laboratory assays were conducted to evaluate larval performance in 2005 and 2006. Among the olive varieties tested, Sevillano, Manzanillo, and Mission olives were the most heavily infested during three consecutive years. The larval performance measurements used were pupal yield, pupal weight, larval developmental time, and pupal emergence time. Ovipositional preference and pupal yield do not seem associated. There were significant differences in pupal emergence time, but these also measures did not reflect ovipositional preference. Two measures on performance did seem related to ovipositional preference; there were significant effects of variety on pupal weight and larval developmental time. Pupae developing in Manzanillo and Sevillano olives were heavier than those developing in less preferred varieties, and larval developmental time was significantly shorter in Sevillano olives relative to the other varieties. Oviposition preference and enhanced larval performance has implications for the pest status of this invasive insect in California.

Genome of Drosophila suzukii, the Spotted Wing Drosophila

Drosophila suzukii Matsumura (spotted wing drosophila) has recently become a serious pest of a wide variety of fruit crops in the United States as well as in Europe, leading to substantial yearly crop losses. To enable basic and applied research of this important pest, we sequenced the D. suzukii genome to obtain a high-quality reference sequence. Here, we discuss the basic properties of the genome and transcriptome and describe patterns of genome evolution in D. suzukii and its close relatives. Our analyses and genome annotations are presented in a web portal, SpottedWingFlyBase, to facilitate public access.