Type and duration of water stress influence host selection and colonization by exotic ambrosia beetles (Coleoptera: Curculionidae).

Fungus-farming ambrosia beetles in the tribe Xyleborini tunnel into plants and trees to establish chambers for cultivating their nutritional fungal mutualists and rearing offspring. Some xyleborine ambrosia beetles preferentially infest and perform better in living but weakened trees. Flood stress predisposes horticultural tree crops to infestation, but the impact of drought stress has not been well studied. Our objectives were to compare the effects of flood stress vs. drought stress on host selection and colonization by xyleborine ambrosia beetles and to assess the duration of flooding. Container-grown Cornus florida L. trees were flood stressed using a pot-in-pot system to submerge the roots in water while drought-stressed conditions were imposed by withholding irrigation and precipitation. When experimental trees were held under field conditions for 14 days, 7.5 × more ambrosia beetles landed on stems of the flood-stressed than on the drought-stressed trees. During two additional experiments over 14 and 22 days, ambrosia beetles tunneled into the flood-stressed trees but not the drought-stressed or standard irrigation trees. By simultaneously deploying trees that were flood stressed for varying lengths of time, it was found that more tunnel entrances, and xyleborine adults and offspring were recovered from trees that were flooded for 1-16 days and 7-22 days than from trees that were flooded for 14-29 days and 28-43 days. These results indicate that acute and severe drought stress does not predispose C. florida to infestation, but flood stress and the duration of flooding influence ambrosia beetle host selection and colonization. Understanding the role of host quality on ambrosia beetle preference behavior will assist with predicting the risk of infestation of these opportunistic insects in horticultural tree crops.

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.

Impact of insecticide programs on pests, the predatory mite Phytoseiulus persimilis, and staked tomato profitability.

BACKGROUND: Various insecticides are available to manage diverse pest complexes in commercial vegetable production, but knowledge gaps exist regarding their overall performance in pest suppression, profitability, and compatibility with biological control. We conducted trials in staked tomatoes in western North Carolina in 2017-2018 to compare how different insecticide programs managed key pests and their interactions with Phytoseiulus persimilis Athias-Henriot, a predator of the twospotted spider mite (TSSM, Tetranychus urticae Koch). Treatments compared no insecticides to broad-spectrum ('hard') foliar applications, selective ('soft') foliar applications, and to chemigation of selective systemic insecticides. Treatment efficacy was based on pest control, net profitability, and Environmental Impact Quotient (EIQ) ratings comparing environmental and human health risks. RESULTS: All programs similarly suppressed aphids, while flower thrips and flea beetle populations were low and unaffected by program. Only the 'hard' foliar program suppressed TSSM (including P. persimilis), which quickly rebounded. This program inhibited biological control, and eventual TSSM suppression was likely caused by P. persimilis immigrating from nearby plots. All programs were generally equivalent in reducing fruit damage. Net profits were similar among insecticide programs, which were significantly greater than in untreated plots. Yield and profit trends were similar both years, but impacted by record flooding in 2018. CONCLUSION: Safer and more selective chemigation and 'soft' foliar programs were as effective and economical as the 'hard' foliar program, while also conserving biological control. These results support existing research demonstrating that improved insecticide use can be integrated with biological control for more profitable and environmentally sustainable vegetable production. © 2022 Society of Chemical Industry.

Diapause Termination in Invasive Populations of the Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) in Response to Photoperiod.

Understanding cues for diapause termination in insects can be valuable in predicting phenological events in their lifecycles. Once identified, such cues can be utilized as a biofix, the point at which the majority of individuals within a population begin to accumulate degree days. We investigated the impact of photoperiod on completion of reproductive diapause in the invasive eastern North American population of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), by exposing diapausing females to varying light regimes in otherwise identical environments. The critical photoperiod estimated to initiate reproductive development in at least 50% of the potential reproductive population was 13.0-13.5 h, with increasing photoperiods coinciding with increased probability of females reproducing, earlier time to first oviposition, and higher rates of fecundity. These data on the species' response to photoperiod are in agreement with previous modeling that predicted the twin constraints of photoperiod and temperature on H. halys reproduction prevents populations that undergo diapause from producing more than two generations annually anywhere within the continental U.S. However, the facultative nature of diapause in H. halys leaves open the possibility that sub-populations may not enter diapause in some conditions, potentially allowing for additional annual generations.

Comparison of Sex Pheromone and Kairomone-Enhanced Pheromone Lures for Monitoring Oriental Fruit Moth (Lepidoptera: Tortricidae) in Mating Disruption and Non-Disruption Tree Fruit Orchards.

Oriental fruit moth, Grapholita molesta (Busck), populations were monitored using standard sex pheromone lures (OFM L2) and kairomone-enhanced lures to aid the interpretation of trap captures with enhanced relative to conventional lures. Initially, comparison of 10 different lures showed that a10X load of OFM pheromone, codlemone, terpinyl acetate, and acetic acid were key components of the most attractive lures (TRE11034 and 1123). Subsequent trapping studies in mating disruption and non-disrupted orchards in the United States and Spain compared trap captures with TRE1123 and OFM L2 lures. Compared to the OFM L2 lure, the TRE1123 lure captured more moths in mating disruption and non-disrupted orchards, caught female moths, improved the precision of mean population estimates, and led to greater resolution of generational flights. Suppression of trap captures in mating disruption versus non-disrupted orchards was similar with both lures. There were significant linear correlations between weekly trap captures with the two lures in the majority of mating disruption and non-disrupted orchards across locations and years. Furthermore, regression of the slopes of trap capture regressions (i.e., attractiveness of enhanced lures relative to sex pheromone lures alone) versus moth density (as measured by mean cumulative moth capture with TRE1123 and OFM L2 lures) exhibited a significant positive relationship in non-disrupted orchards, indicating enhanced lures were relatively more attractive under high population densities. This relationship was not significant in mating disruption orchards, likely due to the density independent, non-competitive mechanism of mating disruption for oriental fruit moth when using high-dose reservoir dispensers.

Comparison of chemigation versus foliar insecticide use: management of lepidopteran larvae and stink bugs in North Carolina field tomatoes with environmental and farmworker benefits.

BACKGROUND: Commercial vegetable production in the United States of America (USA) often relies on foliar insecticide sprays for managing key insect pests. However, foliar applications of insecticides have a number of drawbacks to the health of consumers, farmworkers and the environment. Drip chemigation is the application of pesticides to the soil through trickle (drip) irrigation systems, and can overcome a number of the drawbacks typical of foliar insecticide applications. RESULTS: We conducted a two-year study in five commercial fields of staked tomatoes in western North Carolina to compare the efficacy, economics and environmental impact of drip chemigation versus foliar sprays. Drip chemigation significantly reduced insecticide inputs, utilized more selective and environmentally compatible insecticides, and reduced the time lost to reentry intervals, while maintaining comparable efficacy and economic returns. CONCLUSIONS: Drip chemigation was an effective tool for managing key insect pests, provided a broad range of human and environmental health benefits, and will likely become increasingly cost-effective in the future as insecticide patents expire and more insecticide options become available.

Compatibility of Bifenazate and Phytoseiulus persimilis for Management of Twospotted Spider Mites in North Carolina Staked Tomatoes.

The twospotted spider mite (TSSM, Tetranychus urticae Koch) is a key pest of tomatoes (Solanum lycopersicon L. [Solanales: Solanaceae]) in North Carolina, and its management has relied principally on synthetic acaricides. Augmentative biological control of TSSM is a commonplace and effective management strategy in greenhouses worldwide, but in field-grown vegetable crops biocontrol of TSSM is poorly developed. We conducted small-plot field experiments in 2016 and 2019 to test the ability of the predatory mite, Phytoseiulus persimilis Athias-Henriot, to establish, disperse, and reduce TSSM in staked tomatoes, as well as test their compatibility with a commonly used reduced-risk acaricide, bifenazate (Acramite). Across both years, the most effective treatment for reducing TSSM was the combination of P. persimilis + Acramite. Phytoseiulus persimilis successfully established both years, but its population growth and dispersal were greater in 2016 than 2019. Acramite alone significantly reduced TSSM pressure in 2019 and P. persimilis alone did not reduce TSSM pressure below the control in either year. However, results in 2016 were influenced by the eventual dispersal of P. persimilis into all experimental plots, despite efforts to hinder their movement with corn barriers. Results in 2019 were influenced by the late-season invasion of TSSM into the trial, which delayed P. persimilis releases and influenced their establishment and growth. This study is the first to demonstrate the utility and limitations of P. persimilis in staked field tomatoes, which is a promising option for growers to manage TSSM in tomatoes in the southeast United States.

Baseline Toxicity of the Insecticides Bifenthrin and Thiamethoxam on Halyomorpha halys (Hemiptera: Pentatomidae) Collected From the Eastern United States.

Brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive species in the United States that attacks a wide variety of agricultural commodities including fruits, vegetables, agronomic crops, and ornamental plants. Populations of H. halys adults were collected from four and six states in 2017 and 2018, respectively, and tested using topical applications to establish baseline levels of susceptibility to two commonly used insecticides, bifenthrin and thiamethoxam. A Probit-estimated (95% fiducial limits) LD50 and LD99 of 2.64 g AI/L (1.2-3.84 g AI/L) and 84.96 g AI/L (35.76-716.16 g AI/L) for bifenthrin, and a LD50 and LD99 of 0.05 g AI/liter (1.14E-5-0.27 g AI/L) and 150.11 g AI/L (27.35-761,867 g AI/L) for thiamethoxam, respectively. These baseline levels can be used for future insecticide resistance monitoring in H. halys.

Impact of Temperature Storage Conditions of Halyomorpha halys (Hemiptera: Pentatomidae) Eggs on Parasitism by Anastatus reduvii (Hymenoptera: Eupelmidae).

Brown marmorated stink bug, Halyomorpha halys Stål, is an invasive species of Asian origin that is an important agricultural pest in the eastern United States. Sentinel egg masses are tools used to assess the impact of natural enemies on H. halys populations. To determine the effect of host egg age and storage conditions on their susceptibility to parasitism, H. halys eggs were stored at different temperatures for different lengths of time and then exposed to Anastatus reduvii (Howard), a native natural enemy of H. halys occurring in eastern North America. For eggs stored at 15, 20, and 25°C and then exposed to A. reduvii, the number of host eggs from which parasitoid offspring emerged declined with age of eggs. Control eggs (exposed to parasitoids without being stored) and those eggs stored for only 5.5 degree-days (DD) (=0.5 days) at 25°C yielded the highest percentage of parasitoids at 88.2 and 88.3%, respectively. For eggs stored at 20 and 25°C for 7.3 DD to about 36 DD, offspring emerged from about 58 to 73% of eggs, and total parasitism (emerged + unemerged parasitoids) ranged from about 70 to 80%. Parasitoid emergence was significantly lower for host eggs stored at 15°C for comparable times at 20 and 25°C. Stink bugs nymphs hatched from <0.6% of all eggs. Parasitoid-induced host egg abortion was an important component of egg mortality caused by A. reduvii, with underdeveloped stink bug nymphs, undifferentiated cell contents, and parasitoid host feeding occurring across all storage treatments.

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.

Influence of Weed Manipulation in Field Borders on Brown Stink Bug (Hemiptera: Pentatomidae) Densities and Damage in Field Corn.

Brown stink bug, Euschistus servus (Say), is a damaging pest of corn, Zea mays L. (Cyperales: Poaceae), in the southeastern United States. In North Carolina, during the spring, winter-planted wheat, Triticum aestivum L. (Cyperales: Poaceae), serves as the earliest available crop host, and E. servus seems to prefer this crop over seedling corn. In the absence of wheat in the agroecosystem, weeds serve as a bridge host for a portion of overwintered E. servus populations until they move to corn and other subsequent crops. Our objective was to reduce densities of E. servus in corn by manipulating the weedy field borders with mowing and applications of dicamba herbicide. During the study, multiple species of stink bugs (n =16) were found associated with weed plots. However, E. servus was the predominant (>94%) stink bug species in the corn. In this farmscape, density of E. servus adults in the unmanaged weed plots began declining around the second week of May, followed by an increase in density in adjacent corn plots. This movement coincided with the seedling growth of corn. In 2016, applications of dicamba in the weedy field border resulted in a lower density of E. servus in herbicide-treated weed plots compared with untreated plots. Despite this difference, manipulations of weeds did not lead to any significant changes in density of E. servus adults in corn. Further evidence suggested that a prominent external source of E. servus, other than field-bordering weeds, in the farmscape was likely driving densities in corn.

Effects of Insecticides Used in Organic Agriculture on Anastatus reduvii (Hymenoptera: Eupelmidae) and Telenomus podisi (Hymenoptera: Scelionidae), Egg Parasitoids of Pestivorous Stink Bugs.

Lethal and sublethal effects of insecticides used in organic agriculture were tested against Anastatus reduvii and Telenomus podisi, native North American hymenopteran egg parasitoids of the native Euschistus servus Say (Hemiptera: Pentatomidae) and the invasive Halyomorpha halys Stål. Entrust (spinosad), PyGanic (pyrethrin), Neemix (azadirachtin), and Azera (pyrethrin + azadirachtin) were tested at equivalent field rates of 1×, 0.5×, and 0.1×. Bioassays included insecticide exposure to parasitoids through residue on substrate, parasitized host eggs, and their food source. When exposed to dried residues, Entrust caused 100% mortality at the 0.5× rate to both species; PyGanic, Neemix, and Azera exhibited low toxicity. Exposure of parasitized host eggs to Entrust 1× during the egg stage of parasitoid development reduced parasitoid emergence compared to all other treatments in both species. Anastatus reduvii emergence was also reduced by PyGanic at 0.5× and 1×. Parasitoid emergence from host eggs exposed during the pupal stage was more variable than egg stage exposure; emergence of both species was reduced in 0.5× and 1× rates of PyGanic, and A. reduvii was reduced in the 0.5× rate of Entrust compared to controls. Longevity of emerged parasitoids surviving exposure within host eggs showed that Entrust was more deleterious than Neemix or PyGanic. When A. reduvii was fed insecticide-laced honey, all treatments except Neemix at 0.1× reduced adult longevity compared to the control. These studies demonstrated that insecticides commonly used in organic agriculture can negatively affect two common parasitoids of stink bugs; specifically, negative effects were most pronounced with Entrust, and variable with Neemix and Pyganic.

Phenology of brown marmorated stink bug described using female reproductive development.

Temperature-based degree-day models describe insect seasonality and to predict key phenological events. We expand on the use of a temperature-based process defining timing of reproduction through the incorporation of female reproductive physiology for the invasive pentatomid species Halyomorpha halys, the brown marmorated stink bug. A five-stage ranking system based on ovary development was able to distinguish between the reproductive statuses of field-collected females. Application of this ranking method described aspects of H. halys' seasonality, overwintering biology, and phenology across geographic locations. Female H. halys were collected in the US from NJ, WV, NC, OR, and two sites in PA in 2006-2008 (Allentown, PA only) and 2012-2014. Results identify that H. halys enters reproductive diapause in temperate locations in the fall and that a delay occurs in developmental maturity after diapause termination in the spring. Modification of the Snyder method to identify biofix determined 12.7-hr photoperiod as the best fit to define initiation of reproduction in the spring. Applying the biofix, we demonstrated significant differences between locations for the rate at which the overwintering generation transition into reproductive status and the factors contributing to this difference require further study. For example, after including abiotic variables influencing development such as temperature and photoperiod (critical diapause cue), reproduction occurred earlier in OR and for an extended period in NJ. This data describe a method to investigate insect seasonality by incorporating physiological development across multiple regions that can clarify phenology for insects with overlapping generations.

Behavioral Response of the Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) to Semiochemicals Deployed Inside and Outside Anthropogenic Structures During the Overwintering Period.

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive species from Asia capable of causing severe agricultural damage. It can also be a nuisance pest when it enters and exits anthropogenic overwintering sites. In recent years, pheromone lures and traps for H. halys have been developed and used to monitor populations in field studies. To date, no study has investigated the applicability of these monitoring tools for use indoors by building residents during the overwintering period. Herein, we 1) assessed when in late winter (diapause) and spring (postdiapause) H. halys begins to respond to its pheromone (10,11-epoxy-1-bisabolen-3-ol), 2) evaluated whether pheromone-based tools can be used reliably for monitoring H. halys adults in unheated and heated buildings, and 3) elucidated the potential for indoor management using pheromone-baited traps. A 2-yr trapping study suggested that H. halys began to respond reliably to pheromone-baited traps after a critical photoperiod of 13.5 h in the spring. Captures before that point were not correlated with visual counts of bugs in buildings despite robust populations, suggesting currently available pheromone-baited traps were ineffective for surveillance of diapausing H. halys. Finally, because baited traps captured only 8-20% of the adult H. halys known to be present per location, they were not an effective indoor management tool for overwintering H. halys. Our study contributes important knowledge about the capacity of H. halys to perceive its pheromone during overwintering, and the ramifications thereof for building residents with nuisance problems.

Attraction of the Invasive Halyomorpha halys (Hemiptera: Pentatomidae) to Traps Baited with Semiochemical Stimuli Across the United States.

A recent identification of the two-component aggregation pheromone of the invasive stink bug species, Halyomorpha halys (Stål), in association with a synergist, has greatly improved the ability to accurately monitor the seasonal abundance and distribution of this destructive pest. We evaluated the attraction of H. halys to black pyramid traps baited with lures containing the pheromone alone, the synergist methyl (2E,4E,6Z)-decatrienoate (MDT) alone, and the two lures in combination. Traps were deployed around areas of agricultural production including fruit orchards, vegetables, ornamentals, or row crops in Delaware, Maryland, North Carolina, New Jersey, New York, Ohio, Oregon, Pennsylvania, Virginia, and West Virginia from mid-April to mid-October, 2012 and 2013. We confirmed that H. halys adults and nymphs are attracted to the aggregation pheromone season long, but that attraction is significantly increased with the addition of the synergist MDT. H. halys adults were detected in April with peak captures of overwintering adults in mid- to late May. The largest adult captures were late in the summer, typically in early September. Nymphal captures began in late May and continued season long. Total captures declined rapidly in autumn and ceased by mid-October. Captures were greatest at locations in the Eastern Inland region, followed by those in the Eastern Coastal Plain and Pacific Northwest. Importantly, regardless of location in the United States, all mobile life stages of H. halys consistently responded to the combination of H. halys aggregation pheromone and the synergist throughout the entire season, suggesting that these stimuli will be useful tools to monitor for H. halys in managed systems.

Predicting codling moth (Cydia pomonella) phenology in North Carolina on the basis of temperature and improved generation turnover estimates.

BACKGROUND: The codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is a major worldwide pest of apples, pears and walnuts. A temperature-driven phenological model of codling moth, developed in Michigan, has been utilized in North Carolina and other states for decades. Systematic inaccuracy of this model in predicting moth emergence in North Carolina suggests that the relationship between emergence and temperature differs between the American midwest and southeast, or that additional factors may influence the system. RESULTS: A method was developed to optimize the estimation of generation turnover intervals. Emergence was modeled as a function of heat unit accumulation. Significant differences between emergence predictions based on the resultant model and the existing model developed in Michigan were found. CONCLUSION: A new model of codling moth emergence, incorporating improved estimates for generation turnover for North Carolina, offers predictive improvement with practical importance to management. Differences between the emergence of susceptible and resistant moth populations were also investigated, leading to the suggestion that resistance to insecticides should be considered in future studies of emergence phenology.

Sex pheromone dispenser type and trap design affect capture of dogwood borer.

Using a ternary sex pheromone blend [86:6:6 v:v:v (Z,Z)-3,13-octadecadienyl acetate: (E,Z)-2,13-octadecadienyl acetate: (Z,E)-3,13-octadecadienyl acetate], we tested the effect of dispenser type and trap design for capture of dogwood borer (DWB), Synanthedon scitula Harris (Lepidoptera: Sesiidae) in apple orchards in West Virginia, Virginia, and North Carolina. Wing-style sticky traps baited with polyethylene vial pheromone dispensers captured more male DWB over the first 2 months than traps baited with rubber septum pheromone dispensers. However, catches in vial-baited traps decreased considerably after the first 2 months, possibly due to the antagonistic effect of 3,5-di-tert-butyl-4-hydroxy acetophenone that diffused from the polyethylene vials. By contrast, traps baited with rubber septum dispensers captured DWB males for at least 6 months; over the last four months of the flight season, catches in traps baited with a rubber septum were greater than those in traps baited with a vial dispenser. Therefore, the rubber septum dispenser is recommended for season-long monitoring of DWB. A release-rate study, using laboratory and field-aged dispensers, demonstrated that desorption of DWB sex pheromone from polyethylene vial or rubber septum dispensers followed first order kinetics, with half-lives of 1.6 and 10.7 months, respectively. Several trap designs, including wing-and delta-style sticky traps, and white and green "bucket-style" traps, baited with rubber septum dispensers were compared in commercial apple orchards for catch of DWB. Bucket traps caught more moths when moth populations were high, because the sticky surfaces of the 1C and delta traps likely became saturated. However, among the commercially available traps tested, no particular design gave consistently higher catches. Further work is needed to explore capture mechanisms and maintenance needs of different trap types.

Predicting the emergence of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae), on a degree-day scale in North America.

BACKGROUND: Codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is a major pest of apple, pear and walnut production in North America. Management programs are based on preventing larval entry into the fruit or nut and are typically timed by heat-driven models that are synchronized to field populations by first capture of overwintering moths in pheromone traps. Unfortunately, trap capture is affected by a range of environmental parameters as well as by the use of mating disruption, which makes detecting first flight difficult, thus complicating implementation of management programs. The present goal was to evaluate data collected from a broad range of locations across North America to see whether average first spring emergence times could be predicted. RESULTS: Average emergence time on a degree-day scale from 1 January was predictable using latitude and elevation. Sites at elevations of <400 m fit a simple quadratic equation using latitude, but, when higher elevations were included, a multiple regression using elevation was required. CONCLUSIONS: The present models can be used to simplify management programs for codling moth in areas where heat-driven models that require extensive trapping to synchronize with emergence are currently used.

Development of a rapid resistance monitoring bioassay for codling moth larvae.

BACKGROUND: The codling moth, Cydia pomonella (L.), is one of the most important pests of apple worldwide. Use of insecticides for management of this insect has been extensive and has resulted in resistance development. There are a number of different bioassay methods to monitor for codling moth resistance; however, many are not applicable to new insecticides and most are time consuming. A novel 16-well plasticware bioassay plate containing lyophilized diet was developed for rapid resistance monitoring of codling moth. RESULTS: The contact insecticides acetamiprid and azinphosmethyl were significantly more toxic to neonates than to fourth instars. However, there was no significant difference in LC(50) values between neonates and fourth instars to the ingestion insecticides chlorantraniliprole, methoxyfenozide, novaluron and spinetoram. Field colonies of codling moth were significantly more resistant to methoxyfenozide than susceptible populations. A diagnostic dose of 20 µg mL(-1) (LC(99) ) was established to monitor for codling moth resistance to methoxyfenozide. CONCLUSIONS: The results presented here demonstrate that a novel and rapid bioassay can be used to monitor for codling moth resistance to methoxyfenozide. The bioassay method is relevant to both ingestion and contact insecticides, but a single diagnostic dose, regardless of larval age, is only relevant to ingestion insecticides. Age-dependent diagnostic doses are likely necessary for contact insecticides.

Life stage toxicity and residual activity of insecticides to codling moth and oriental fruit moth (Lepidoptera: Tortricidae).

The codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), are two key pests of apple (Malus domestica Borkh.) in North Carolina. Growers extensively relied on organophosphate insecticides, primarily azinphosmethyl, for > 40 yr to manage these pests. Because of organophosphate resistance development and regulatory actions, growers are transitioning to management programs that use new, reduced-risk, and OP-replacement insecticides. This study evaluated the toxicity of a diversity of replacement insecticides to eggs, larvae, and adults, as well as an assessment of their residual activity, to codling moth and oriental fruit moth. Laboratory-susceptible strains of both species were used for all bioassays. Fresh field-harvested apples were used as a media for assessing the ovicidal activity of insecticides. For larval studies, insecticides were topically applied to the surface of lima bean-based diet, onto which neonates were placed. Toxicity was based on two measures of mortality; 5-d mortality and development to adult stage. Ovicidal bioassays showed that oriental fruit moth eggs were generally more tolerant than codling moth eggs to insecticides, with novaluron, acetamiprid, and azinphoshmethyl having the highest levels of toxicity to eggs of both species. In contrast, codling moth larvae generally were more tolerant than oriental fruit moth to most insecticides. Methoxyfenozide and pyriproxyfen were the only insecticides with lower LC50 values against codling moth than oriental fruit moth neonates. Moreover, a number of insecticides, particularly the IGRs methoxyfenozide and novaluron, the anthranilic diamide chlorantriliprole, and the spinosyn spinetoram, provided equal or longer residual activity against codling moth compared with azinphosmethyl in field studies. Results are discussed in relation to their use in devising field use patterns of insecticides and for insecticide resistance monitoring programs.