Evaluating invasion risk and population dynamics of the brown marmorated stink bug across the contiguous United States.

BACKGROUND: Invasive species threaten the productivity and stability of natural and managed ecosystems. Predicting the spread of invaders, which can aid in early mitigation efforts, is a major challenge, especially in the face of climate change. While ecological niche models are effective tools to assess habitat suitability for invaders, such models have rarely been created for invasive pest species with rapidly expanding ranges. Here, we leveraged a national monitoring effort from 543 sites over 3 years to assess factors mediating the occurrence and abundance of brown marmorated stink bug (BMSB, Halyomorpha halys), an invasive insect pest that has readily established throughout much of the United States. RESULTS: We used maximum entropy models to estimate the suitable habitat of BMSB under several climate scenarios, and generalized boosted models to assess environmental factors that regulated BMSB abundance. Our models captured BMSB distribution and abundance with high accuracy, and predicted a 70% increase in suitable habitat under future climate scenarios. However, environmental factors that mediated the geographical distribution of BMSB were different from those driving abundance. While BMSB occurrence was most affected by winter precipitation and proximity to populated areas, BMSB abundance was influenced most strongly by evapotranspiration and solar photoperiod. CONCLUSION: Our results suggest that linking models of establishment (occurrence) and population dynamics (abundance) offers a more effective way to forecast the spread and impact of BMSB and other invasive species than simply occurrence-based models, allowing for targeted mitigation efforts. Implications of distribution shifts under climate change are discussed. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Reduced Infestation by Xylosandrus germanus (Coleoptera: Curculionidae: Scolytinae) in Apple Trees Treated with Host Plant Defense Compounds.

The ambrosia beetle Xylosandrus germanus (Blandford) is an invasive pest that has caused tree decline and death in numerous NY dwarf apple orchards during the past ten years, despite efforts to control them using trunk sprays of chlorpyrifos or pyrethroids, either alone or combined with the repellent verbenone. From 2017 to 2019, we tested trunk applications of different repellents and plant defense compounds for protection against X. germanus in potted apple trees adjacent to infested orchards. Treatments included topical formulations of verbenone and methyl salicylate (MeSa), alone and in combination, at different rates and timings. Additional treatments evaluated included the systemic acquired resistance activators acibenzolar-S-methyl, Reynoutria sachalinensis extract, and salicylic acid. The combination verbenone+MeSa treatments had the lowest incidences of attack sites and galleries containing adults or brood, although results varied among years. In a separate trial, we found no significant difference in numbers of adults caught in ethanol-baited traps placed 5-20 m from an apple bolt treated with the verbenone+MeSa repellent, suggesting that the repellent's effect did not extend to those distances from the treated target. Cross-sectional discs of trunk tissue sampled in August were analyzed for levels of phytohormones. Quantities of ergosterol, abscissic acid, salicylic acid, jasmonic acid, methyl salicylate, methyl jasmonate, trans-cinnamic acid, and indole-3-cinnamic acid did not significantly vary across treatments; however, trees with greater beetle damage contained higher levels of jasmonic and salicylic acid, which are key molecules in plant defense pathways.

Impact of Nosema maddoxi on the survival, development, and female fecundity of Halyomorpha halys.

Nosema maddoxi Becnel, Solter, Hajek, Huang, Sanscrainte, & Estep, a microsporidian species native to the United States, has been found infecting the invasive brown marmorated stink bug, Halyomorpha halys (Stål). Microsporidian infections in insects often shorten lifespans, decrease fecundity, prolong development, and stunt growth. This study was conducted to determine the impact of N. maddoxi on H. halys fitness. Adult females (2 doses) and nymphs (1 dose) drank suspensions of N. maddoxi spores to promote infection. Adult females receiving a high dose died faster than the controls. Nosema maddoxi infections impacted female egg production and egg viability at both doses compared with the controls. Infections were transmitted to 34.9% of adult males caged with infected females. As the number of days after inoculation increased, infection intensity (# spores found within an infected individual) for both adult treatments transitioned from low-intensity to high-intensity. Infected nymphs died significantly sooner than the controls. Of the treated nymphs, 55.9% died before molting into the fourth instar and only 26.5% eclosed to adults. Nymphal development rate and size were not impacted by N. maddoxi infection. These results indicate that N. maddoxi infection can negatively impact the lifespan of adult females, female fecundity, egg viability, and nymphal survival, which we hypothesize would negatively impact H. halys population densities.

Season-Long Monitoring of the Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Throughout the United States Using Commercially Available Traps and Lures.

Reliable monitoring of the invasive Halyomorpha halys abundance, phenology and geographic distribution is critical for its management. Halyomorpha halys adult and nymphal captures on clear sticky traps and in black pyramid traps were compared in 18 states across the Great Lakes, Mid-Atlantic, Southeast, Pacific Northwest and Western regions of the United States. Traps were baited with commercial lures containing the H. halys pheromone and synergist, and deployed at field sites bordering agricultural or urban locations with H. halys host plants. Nymphal and adult captures in pyramid traps were greater than those on sticky traps, but captures were positively correlated between the two trap types within each region and during the early-, mid- and late season across all sites. Sites were further classified as having a low, moderate or high relative H. halys density and again showed positive correlations between captures for the two trap types for nymphs and adults. Among regions, the greatest adult captures were recorded in the Southeast and Mid-Atlantic on pyramid and sticky traps, respectively, with lowest captures recorded in the West. Nymphal captures, while lower than adult captures, were greatest in the Southeast and lowest in the West. Nymphal and adult captures were, generally, greatest during July-August and September-October, respectively. Trapping data were compared with available phenological models showing comparable population peaks at most locations. Results demonstrated that sticky traps offer a simpler alternative to pyramid traps, but both can be reliable tools to monitor H. halys in different geographical locations with varying population densities throughout the season.

Xylosandrus germanus (Coleoptera: Curculionidae: Scolytinae) Occurrence, Fungal Associations, and Management Trials in New York Apple Orchards.

Xylosandrus germanus (Blandford) has caused increasing damage in high-density New York apple orchards since 2013, resulting in tree decline and death. We documented their occurrence and timing in > 50 orchards using ethanol-baited traps from 2014 to 2016. First captures ranged from 48 to 83 degree days (base 10 °C) from 1 January. Captures were numerically higher at the orchard-woods interface than within the orchard interior, but differences were not significant in locations with lower populations. Control using insecticide trunk sprays was tested in potted, waterlogged apple trees placed in orchards and nurseries, and inside wooded areas adjacent to orchards. A verbenone repellent was used in combination with trunk sprays to improve control. Overall, insecticide sprays were inconsistent and marginal in preventing new infestations. Chlorpyrifos significantly reduced infestations versus lambda-cyhalothrin and untreated trees at one location in the 2015 orchard trials, and versus untreated trees at one location in the 2016 nursery trials, but otherwise performed no better than other treatments. The addition of verbenone to either the check or permethrin treatments resulted in significantly fewer attack sites containing brood at one orchard site in 2016. Chlorpyrifos, lambda-cyhalothrin, and permethrin significantly reduced the number of attack sites containing adults compared with untreated trees at one nursery trial location in 2016, but were otherwise ineffective in reducing numbers of trees in other locations and infestation categories. We found several fungal and bacterial species associated with X. germanus and its infestation of apples. These microbes likely play a minimal role in apple decline.

Novel barriers to prevent dogwood borer (Lepidoptera: Sesiidae) and rodent damage in apple plantings.

We evaluated a combination of noninsecticidal alternatives to control trunk-damaging dogwood borer, Synanthedon scitula (Harris), consisting of novel barrier technologies, used alone or in combination with mating disruption. Barrier formulations evaluated included fibrous barriers of nonwoven ethylene vinyl acetate (EVA) and nonfibrous barriers of rubberized paint (elastomer) used in building coatings. To examine efficacy of dogwood borer control in orchards, all barrier trials were replicated in field tests, both in combination with mating disruption and without it. Trunk inspections to determine whether mating disruption and barriers effectively reduced actual tree infestation showed pheromone disruption significantly reduced infestation compared with the untreated check, but was not as effective as trunk handgun sprays of chlorpyrifos. EVA trunk barriers were effective in preventing borer infestation compared with untreated trees. The elastomer did not differ from the check or the EVA treatment. There was no interaction between disruption and barrier treatments. Barrier field life and durability was assessed over 2 yr by comparing degradation over time due to weathering and other environmental effects including animal damage. The EVA persisted and remained more intact than the elastomer, but was in need of reapplication after 2 yr. Barriers were also screened for efficacy against voles in small-plot trials in nonorchard locations with known high vole pressure; they were tested either alone, combined with a repellent (thiram), or, in the case of the elastomer only, combined with an abrasive (sand). Only the EVA significantly lowered vole chewing damage relative to the untreated checks.

Relationship between plant phenology and Campylomma verbasci (Hemiptera: Miridae) damage to apple fruit.

Damage to apple (Malus domestica Borkhausen) by Campylomma verbasci (Meyer), has occurred even when effective insecticides are applied against nymphs present at the petal fall stage. However, insecticide application at pink bud prevents damage more effectively than when the same insecticides are applied at petal fall. We tested the hypothesis that most mullein bug damage occurs between bloom and petal fall by using two approaches. In the first, we caged naturally occurring nymphs on 'Red Delicious' limbs and restricted their possible infestation timing by applying insecticides both before cages were placed and also through the cage at various crop stages from bloom through fruit set. In a second approach, we caged Red Delicious and 'McIntosh' fruit clusters and introduced either small or large nymphs at various times from bloom through 3 wk after fruit set. Fruit damage on both varieties was greatest when small nymphs were introduced between bloom and petal fall; damage was uncommon from small nymphs introduced after fruit were ≍6 mm, and absent after the 13 mm size. However, damage was greater in cages into which large nymphs were introduced at 10-13 mm, than in untreated control cages. Fruit damage levels were equivalent on McIntosh and Red Delicious. We compared emergence of nymphs from McIntosh shoots with adjacent plantings of other, more susceptible cultivars by forcing hatch in the laboratory from cuttings collected in late winter. Significantly more nymphs hatched from susceptible varieties than from McIntosh, suggesting possible differences in levels of oviposition.

Effectiveness of odor-baited trap trees for plum curculio (Coleoptera: Curculionidae) monitoring in commercial apple orchards in the northeast.

The plum curculio, Conotrachelus nenuphar (Herbst), is a key pest of pome and stone fruit in eastern and central North America. For effective management of this insect pest in commercial apple (Malus spp.) orchards in the northeastern United States and Canada, one of the greatest challenges has been to determine the need for and timing of insecticide applications that will protect apple fruit from injury by adults. In a 2004-2005 study, we assessed the efficacy and economic viability of a reduced-risk integrated pest management strategy involving an odor-baited trap tree approach to determine need for and timing of insecticide use against plum curculio based on appearance of fresh egg-laying scars. Evaluations took place in commercial apple orchards in seven northeastern U.S. states. More specifically, we compared the trap-tree approach with three calendar-driven whole-block sprays and with heat-unit accumulation models that predict how long insecticide should be applied to orchard trees to prevent injury by plum curculio late in the season. Trap tree plots received a whole-plot insecticide spray by the time of petal fall, and succeeding sprays (if needed) were applied to peripheral-row trees only, depending on a threshold of one fresh plum curculio egg-laying scar out of 25 fruit sampled from a single trap tree. In both years, level of plum curculio injury to fruit sampled from perimeter-row, the most interior-row trees and whole-plot injury in trap tree plots did not differ significantly from that recorded in plots subject to conventional management or in plots managed using the heat-unit accumulation approach. The amount of insecticide used in trap tree plots was reduced at least by 43% compared with plots managed with the conventional approach. Advantages and potential pitfalls of the bio-based trap tree approach to plum curculio monitoring in apple orchards are discussed.

Evaluation of the environmental impact of apple pest control strategies using pesticide risk indicators.

Various pesticide risk indicators have been developed for estimating pesticide impact on human health and the environment. The present work applied a pesticide risk indicator to estimate change in pesticide risk in apple production between 2001 and 2009. The "Environmental Impact Quotient" was used, which evaluates potential impacts of pesticide active ingredients on farm workers, consumers, and nontarget organisms. A modified Environmental Impact Quotient was also tested, which accounts for all ingredients in the formulation presenting a health or environmental hazard, as identified in the Security Data Sheet. Irrespective of the rating system applied, an overall average improvement in environmental impact of apple protection strategies was indicated ranging from 23 to 24%. Hazard reduction was more significant when estimated per treatment, and was higher for acaricides and insecticides than for fungicides. Improvement appeared to be a consequence of using more selective and more effective active ingredients, applying alternative pest control techniques, compulsory periodic sprayer calibration, and wider use of dwarfing orchards. The modified Environmental Impact Quotient does not overcome all limitations regarding accuracy of pesticide risk indicators, but its ease of use in relying on official, easily accessible data, and the consistency of its results, makes it a good candidate for monitoring the success of reduced risk policies.

Incidence and control of dogwood borer (Lepidoptera: Sesiidae) and American plum borer (Lepidoptera: Pyralidae) infesting burrknots on clonal apple rootstocks in New York.

Surveys were conducted in the major apple growing regions of New York state to determine the incidence of borers infesting burrknots on clonal apple rootstocks. Dogwood borer, Synanthedon scitula (Harris), was generally prevalent throughout the state, but American plum borer, Euzophera semifuneralis (Walker), was limited to western New York apple orchards near infested stone fruit trees. Insecticides evaluated in the field for efficacy against both borers were chlorpyrifos, endosulfan, indoxacarb plus oil, methoxyfenozide, fenpropathrin, and kaolin clay. Also, white latex paint was tested alone and mixed with chlorpyrifos. One application of chlorpyrifos applied at the petal fall developmental stage was equivalent to chlorpyrifos applied at petal fall and again in mid-July, and it provided season-long control of dogwood borer and American plum borer. One application of chlorpyrifos applied any time between the half-inch green developmental stage and petal fall, or after harvest the previous season, controlled both overwintered and summer brood larvae of dogwood borer. Multiple applications of fenpropathrin, indoxacarb plus oil, and endosulfan applied during the dogwood borer flight period controlled the summer brood.

Effect of high-carbon dioxide atmospheres on infestations of apple maggot (Diptera: Tephritidae) in apples.

Short-term storage regimens containing elevated atmospheres of carbon dioxide (CO2) were evaluated for their ability to disinfest newly harvested 'McIntosh' apples of apple maggot, Rhagoletis pomonella (Walsh). Infested fruits containing newly laid eggs were either placed directly into the high-CO2 atmosphere at 10 degrees C to expose this life stage, or else held first for 7 d at room temperature, to allow development to the neonate larval stage. Treatment combinations consisted of three different CO2 levels (10.6, 14.9, and 19.0% CO2) and two periods of exposure (7 and 14 d). Apple maggot eggs subjected to the treatments always exhibited some survival, which was lower for the 14-d than the 7-d exposure periods. In contrast, newly hatched larvae were less able to survive the treatments. The 7-d exposure allowed low levels of survival of this life stage, but virtually none survived the 14-d exposure period. To determine the age at which eggs become more susceptible to high-CO2 atmospheres, infested fruits containing eggs three or 3d old were submitted to a 14-d exposure to 19.0% CO2. Survival of 3-d old eggs was similar to that of eggs exposed at an age of 1 d or less, but this dropped to near zero for 5-d old eggs, indicating an increase in susceptibility sometime during the 3-5-d age range. Fruits exposed to 19.0% CO2 for 14 d were significantly firmer than untreated fruits. No apparent browning, internal breakdown or other fruit defects were detected in any of the treatments.