Peter Smytheman

Drosophila suzukii (Matsumura) is an invasive pest of berries and cherries in Washington State, and as a direct fruit feeder, has become a key pest in the affected crops. The recent interest in classical biological control using Asian parasitoids in the family Figitidae highlights the need for effective sampling methods. Whether adventively established or released by research labs, surveys and follow-up sampling for parasitoid detection is an important step in tracking their spread and ultimately, the success of release endeavors. In this study, we examined 5 proposed sampling approaches to determine their capture rates, relative effort, and ease of use. The study was conducted over 2 seasons in northwestern Washington State, where 2 Asian figitids, Ganaspis kimorum Buffington and Leptopilina japonica Novkovic & Kimura, were adventively established. Liquid-based D. suzukii traps using either wine-vinegar bait or an artificial lure captured ca. 10.6- to 256.6-fold more figitids than field collected fruit. However, liquid traps yielded mediocre specimens (for morphological identification or PCR analyses) and required considerable time to sort out the target species from by-catch. Yellow sticky cards with a synthetic lure had a similar capture rate as fruit sampling, but with poorer quality specimens. Fruit sampling yielded higher quality specimens and allowed for an association (including % parasitism) between host and parasitoid but was restricted to periods when ripe fruit was available. Deploying D. suzukii-infested fruit sentinels was labor intensive and captured only one adult figitid over 2 yr, suggesting that this was the least practical method.

The geographic distribution and relative abundance of 2 adventive Asian parasitoids (Ganaspis kimorum Buffington and Leptopilina japonica Novković & Kimura) (Hymenoptera: Figitidae) of spotted-wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae) in Washington state were surveyed from 2020 to 2024 using bait or lure traps. G. kimorum and L. japonica were first detected in 2020 to 2021 in western Washington. However, their distribution in eastern Washington, which produces the majority Washington’s vulnerable specialty crops, was of interest for establishing a baseline for future biological control efforts. A clear picture emerged regarding the current distribution of the 2 Asian species, and a cosmopolitan figitid, Leptopilina heterotoma (Thompson), which attacks other Drosophila spp. Adventive populations of G. kimorum were only found west of the Cascade Mountains; the few specimens recovered in eastern Washington were found near release sites. Conversely, L. heterotoma was rarely detected using jar traps in western Washington, but was the most abundant of the figitid species found in eastern Washington. L. japonica was common and abundant in both regions, but more so in western Washington. The unaided establishment of L. japonica in eastern Washington may presage its future impact as a biological control agent in this region.

The invasive brown marmorated stink bug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), has spread throughout most of Washington (WA) State since its detection in 2012. While it has emerged as a major agricultural and nuisance pest in the Pacific Northwest (PNW) west of the Cascade Mountains, pest pressure in the major tree fruit-growing areas in semi-arid northern and central WA State remains low. The reasons for this are unclear, although both biotic and abiotic conditions may be contributing factors. We evaluated the suitability of a common shrub-steppe/riparian corridor plant assemblage for supporting H. halys development from egg to adult in summer and fall through controlled feeding studies. Nymphs successfully completed development on this diet of PNW native plants, though it generally resulted in lower survivorship and adult weight and longer developmental times than a modified colony diet or a diet of known hosts from the eastern United States. These developmental data were used to parameterize stage-structured matrix models to predict the impact of diet and extreme heat events on H. halys population growth. The predicted net reproductive rate (R₀) of H. halys was consistently and substantially reduced by a diet of PNW native plants, and heat shock imposed further severe reductions in R₀. Our results suggest that the combined population effects of suboptimal plant host quality and regional heat waves may explain the lack of landscape-level H. halys pest pressure in semi-arid regions of the PNW.

Monitoring is an important element in management programs for Drosophila suzukii (Matsumura), helping users to avoid prophylactic treatments. Factors such as attractiveness, sensitivity, selectivity, longevity, and ease of use must be considered when developing a trap and lure system for monitoring and thresholds. We examined various baits and lures over a 5-yr period in sweet cherry orchards in the semiarid climate of eastern Washington. Using a jar trap, the attractants were evaluated for attractiveness (maximum capture), selectivity for D. suzukii (vs. other Drosophila species), and sex ratio of captured D. suzukii. We examined the relative performance of the attractants during periods of low (≈1 D. suzukii per trap per week) and high (232 D. suzukii per trap per week) density over the course of the growing season, which usually corresponded to mid-summer and autumn temperatures, respectively. The Scentry lure was consistently the most attractive lure, capturing the highest numbers of adult D. suzukii over the series of tests, but also had the highest levels of by-catch. Recipe-based baits (yeast, wine-vinegar, and apple cider vinegar) captured fewer D. suzukii overall, although the commercial baits Dros’Attract and Suzukii Trap were comparable to the Scentry lure in late season tests. The Trécé lures were consistently the most selective of the attractants, but had generally lower D. suzukii captures. Sex ratio varied widely among and within the tests, but with no consistent pattern among the various attractants. All attractants were successful in capturing flies, and the choice of attractant depends on the constraints and goals of the user.

This note describes the development of a plug-in imaging system for pheromone delta traps used in pest population monitoring. The plug-in comprises an RGB imaging sensor integrated with a microcontroller unit and associated hardware for optimized power usage and data capture. The plug-in can be attached to the top of a modified delta trap to realize periodic image capture of the trap liner (17.8 cm × 17.8 cm). As configured, the captured images are stored on a microSD card with ~0.01 cm² pixel⁻¹ spatial resolution. The plug-in hardware is configured to conserve power, as it enters in sleep mode during idle operation. Twenty traps with plug-in units were constructed and evaluated in the 2020 field season for codling moth (Cydia pomonella) population monitoring in a research study. The units reliably captured images at daily interval over the course of two weeks with a 350 mAh DC power source. The captured images provided the temporal population dynamics of codling moths, which would otherwise be achieved through daily manual trap monitoring. The system’s build cost is about $33 per unit, and it has potential for scaling to commercial applications through Internet of Things-enabled technologies integration.

Erythritol, an artificial sweetener, has shown promise as an organic, human-safe insecticide. Recently, erythritol applications were shown to be successful at controlling pear psylla (Cacopsylla pyricola (Förster)) (Hempitera: Psyllidae), the most important pest of pear in the Pacific Northwest, USA. Twospotted spider mite (Tetranychus urticae Koch) (Trombidiformes: Tetranychidae) and pear rust mite (Epitrimerus pyri (Nalepa)) (Trombidiformes: Eriophyidae) can also be highly damaging pear pests. Their common natural enemy, Galendromus occidentalis (Nesbitt) (Mesostigmata: Phytoseiidae), can provide biological control if selective pesticides are used for managing other pests. Through a series of bioassays, we sought to determine whether erythritol could also be used for controlling either species of pest mite. We also examined whether erythritol had acute or sublethal impacts on G. occidentalis, through a variety of exposure methods. Effects examined included mortality, fecundity, prey consumption, and locomotion. We determined that a high concentration of erythritol (30%) had efficacy against both pest mite species and caused arresting behavior in twospotted spider mite. Erythritol caused little acute mortality in G. occidentalis, but did reduce fecundity and prey consumption through some exposure methods. Through motion-capture software, we determined that this is primarily due to reduced movement, likely caused by difficulty walking on residues and excessive grooming behavior. Because the predatory mite non-target effects were less acute than those for the two pest mites, we concluded that erythritol could likely be integrated into pear IPM with little or no disruption of mite biological control.

The objective of this study was to assess the efficacy of pesticides against WAA in apple. The trial was conducted in a 1.2-acre apple research block at Washington State University’s Sunrise orchard near Rock Island, WA. The trees were planted in 2007 at a spacing of 3 × 10 ft with alternating rows of four cultivars: ‘Golden Delicious’, ‘Jonagold’, ‘Gala’, and ‘Fuji’. The plots consisted of three trees in a row in the ‘Fuji’ and ‘Jonagold’ rows, with plots separated by 1 to 3 buffer rows. Blocks (reps A–D) were assigned on the basis of a pre-treatment count on 30 Jun, with the 16 treatments randomized within blocks in a randomized complete block design ( Table 1). All treatments were applied on 8 Jul 2020 with two additional applications at 1-wk intervals (15 and 22 Jul) for the two TetraCURB treatments (total of three applications). Applications were made with an airblast sprayer calibrated to deliver 100 gpa. WAA were sampled using timed counts of colonies (2 min/3-tree plot) pre-treatment (30 Jun), 2 DAT, and at ca. weekly intervals thereafter. Data were analyzed using a mixed-model analysis of variance for an RCB design with a Tukey’s HSD mean separation test. Means were compared on each individual count date and also for an average of the counts from 6 to 28 DAT.