Louis Nottingham

Pear psylla, Cacopsylla pyricola (Förster), is a key pest of pears in the Pacific Northwest United States. Overwintering adults (winterforms) recolonize orchards in late winter from habitat outside orchards. To reduce winterform colonization and subsequent damage, sprays of the repellent particle film, kaolin clay, are recommended from late dormant through bloom. However, many pear growers struggle to make early sprays due to the danger of driving tractors over hilly terrain with lingering winter moisture. To address this challenge, we tested fall applications of kaolin (Surround WP) for suppression of pear psylla the following spring. Experiments were performed on potted trees and commercial orchard-sized plots, with fall kaolin treatments made at 112 kg/ha (120 g/L). Pear psylla adult and egg densities were measured by visual counts, and kaolin residue stability was assessed by relative whiteness of branches using ImageJ. In the days immediately after kaolin applications (fall and spring), kaolin significantly reduced pear psylla adult numbers and increased branch whiteness. Fall kaolin residues visibly declined over the winter, but branches often remained significantly whiter than checks at spring assessments. Likewise, fall kaolin often resulted in significantly fewer adults and eggs than checks the following spring. This study demonstrates that residues from fall-applied kaolin can remain through the winter and reduce pear psylla colonization the following spring. This tactic will be advantageous in orchards that are difficult to spray in early spring, and as a general addition to the pear integrated pest management toolkit.

Integrated pest management programs often use pesticides alongside behavioral tactics, such as mating disruption, to manage pests. Pest management using biotremology, the study of vibrations produced by organisms, is gaining attention but requires substantial knowledge of pests and their environment. Here, we built on previous characterizations of vibrational mating signals in pear psylla to assess if pear psylla (Cacopsylla pyricola Förster) communication behavior can be exploited for pest management. Specifically, we conducted greenhouse experiments to test the efficacy of 3 vibrational playback treatments for mating disruption: (i) control, (ii) white noise, and (iii) male mating signals, using 2 delivery methods: (i) plant substrate and (ii) trellis wire; these 2 methods assessed whether devices attached directly to pear saplings or trellis wire supporting saplings provided similar results. We also conducted experiments in pear orchards to assess effectiveness of vibrational playbacks as trap supplements. In the greenhouse, white noise and male mating signals delivered through plant substrates reduced pear psylla offspring in 1 of 3 experiments, but never when delivered through trellis wires. Sticky traps in orchards supplemented with vibrational signals trapped more adults and females than sticky traps alone. The results of this study suggest that pear psylla vibrational communication may be exploited for pest control and pest monitoring, but variable efficacy among experiments suggests a need for further examination into delivery methods.

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.

A recent outbreak of X-disease, caused by the phytoplasma “Candidatus Phytoplasma pruni,” has severely harmed stone fruit production in the Pacific Northwest region of the United States. X-disease is spread by leafhopper vectors, primarily Colladonus montanus reductus in Washington and Euscelidius variegatus in Oregon. Growers rely on frequent insecticide applications and removal of infected trees, but these management recommendations originate from California when the last outbreak occurred in the 1980s. To update insecticide efficacy information for X-disease vectors, we evaluated 23 commercially available insecticidal products via direct spray, spray residues, systemic uptake by plants, or repellency assays. In direct spray bioassays, insecticides containing pyrethrins, pyrethroids, neonicotinoids, or organophosphates caused 100% mortality of C. m. reductus after 24 h. More selective chemistries including cyantraniliprole, flonicamid, and botanical essences also caused high mortality (>70%) of C. m. reductus (Van Duzee). For residues, neonicotinoids and pyrethroids caused the greatest mortality (≥70%) of C. m. reductus. Systemic uptake of neonicotinoids caused significantly higher mortality (51.4% to 100%) than controls (1.4% to 32.4%) of C. m. reductus. Direct sprays and 5 d residues of neonicotinoids caused high mortality (>70%) of E. variegatus. Cherry leaves treated with either kaolin clay or diatomaceous earth had 80% to 90% fewer C. m. reductus residing on them than the controls. Overall, pyrethroids and neonicotinoids were the most effective, but more selective chemistries and repellent clays showed potential and need to be validated in field conditions. Future work should integrate insecticides, repellents, and cultural tactics with phenology-based treatment timings to improve management sustainability.

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 European earwig, Forficula auricularia L. (sensu lato), has a dual role in temperate tree fruit crops—a pest of stone fruit and a predator of key pests in pome fruit. Some growers trap earwigs in crops where they are pests, subsequently releasing them in pome fruit as an augmentative biological control strategy. Effective earwig monitoring and trapping are critical for understanding their biological control potential in orchards. Traps made of rolled, corrugated cardboard have long been used for earwig monitoring; however, no standardized studies have investigated improvements to them. In a series of trials, we explore options to improve traps by testing different trap materials, sizes, positioning on the tree, and time in the field, in addition to the lures and baits. We found that cardboard traps had higher earwig catch than black or translucent plastic traps. There were diminishing returns in earwig capture for increased trap length, plateauing at ~30 cm. Traps placed on the main trunk captured more earwigs than traps on the base or near the end of branches. Lures and baits mostly did not increase trap efficacy, except fish sauce which inconsistently increased earwig captures. The use of plastic bottles to contain the cardboard traps greatly reduced trap catch. Finally, we found evidence that traps left in the field for longer periods of time can increase earwig capture, possibly due to the accumulation of earwig aggregation pheromone. Overall, the standard unbaited corrugated cardboard trap was the most effective and practical earwig monitoring trap.

Conservation biological control in agriculture primarily relies on avoiding pesticides that may harm key natural enemies. In temperate tree fruit crops, the European earwig, Forficula auricularia (L.) has only recently become appreciated as an important predator of economic pests, particularly woolly aphids and pear psylla. Therefore, the non-target effects of orchard pesticides on earwigs are largely understudied. This is particularly true for herbicides, which earwigs are likely to be exposed to due to their foraging behavior moving between the canopy and the ground cover. We tested residues of formulated pesticides (8 insecticides and 7 herbicides) commonly used in tree fruit crops for lethal and sublethal (movement, predation rate) effects on adult female earwigs. Two herbicides, paraquat and glufosinate, and one insecticide, spinetoram, were acutely toxic to earwigs within 72 h. No tested pesticides altered earwigs’ movement or resting behavior compared to the control. The insecticides spinosad and cyantraniliprole and the herbicides 2,4-D, glufosinate, halosulfuron, rimsulfuron, and oxyfluorfen reduced earwig predation on green peach aphids. Therefore, these pesticides may reduce earwig predation on pests in orchards. Our results suggest that some pesticides are of greater risk, and thus, should be carefully considered or better timed when used in tree fruit orchards where earwigs are considered for conservation or augmentative biological control.

Pear psylla, Cacopsylla pyricola (Foërster), is the most economically harmful arthropod pest of pears in the Pacific Northwest (PNW). The phloem-feeding nymphs produce a sticky, sugar-based excrement called honeydew, which causes cosmetic fruit injury, tree stress, and inconvenience to orchard workers. Management of pear psylla has historically prioritized season-long spraying with insecticides that have substantial nontarget effects on natural enemies. However, control has been an ongoing challenge in many growing regions due to pear psylla’s resistance to insecticides, and natural enemies are virtually absent in orchards with aggressive pesticide programs near harvest, leading to rapid increases in pear psylla. Subsequently, excessive numbers of overwintering pear psylla create a regional overabundance of the pest the following spring. Integrated pest management (IPM) programs for pear psylla prevent this cycle with effective cultural tactics and insecticides that are minimally disruptive to natural enemies. Still, IPM adoption seems to be regionally variable. The major growing region of the Wenatchee Valley in Washington State has been reluctant to adopt IPM and, consequently, continues to struggle with pear psylla management. Other areas, such as Hood River, Oregon, and Okanogan, British Columbia, have made significant improvements in pear psylla management through the adoption of area-wide IPM. This review will provide an overview of pear psylla biology, pest status in the PNW, primary IPM tactics, and various elements that have either challenged or advanced the pear industry’s adoption of IPM.