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Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are often the target of insecticide seed treatments commonly used in corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production in North America. Nevertheless, there is a lack of knowledge of the species, life history, and economic impact of wireworms present in these agroecosystems. An extensive survey of wireworms was conducted in corn and soybean fields in Ontario, Canada, from 2014 to 2017 to document species distribution and co-occurrence and to identify risk factors related to their abundance. In total, 4,332 specimens were collected from 1,245 different sampling records. The dominant species collected was Limonius agonus (Say) (Coleoptera: Elateridae) comprising 71.5% of the specimens. The remaining wireworm specimens were identified as Hypnoidus abbreviatus (Say), Melanotus similis (Kirby), M. cribulosus (LeConte), M. depressus (Melsheimer), M. communis (Gyllenhal), Agriotes mancus (Say), Aeolus mellillus (Say), and Hemicrepidius spp (Germar). Multiple wireworm species were found to commonly occur within the same field and the same sample. Path analysis was conducted to investigate whether site, soil, and agronomic characteristics influenced wireworm distribution and abundance. Several significant relationships were found between wireworm species and geographic factors, soil texture, and agronomic practices. The results of this survey provide critical information that can be used to improve integrated pest management of the major wireworm genera found in corn and soybean agroecosystems in Ontario. [ABSTRACT FROM AUTHOR]

Insect migrations have ecological and economic impacts, particularly in agriculture. However, there is limited knowledge about the migratory movements of pests at the continental scale, which is an important factor influencing the spread of resistance genes. Understanding the migratory patterns of economic pests, like Helicoverpa zea (Boddie), is essential for improving Integrated Pest Management (IPM) and Insect Resistance Management (IRM) strategies. In this study, we used stable hydrogen isotopic ratios in wing tissue as a biogeochemical marker to examine migratory patterns and estimate the native origins of H. zea individuals collected across a wide latitudinal gradient in North America. Samples collected at higher latitudes (Ontario, Canada and Minnesota, USA) exhibited a greater proportion (60%–96%) of nonlocal individuals, with an increased probability of origin from the southeastern United States. Populations from mid-latitudes (Florida, North Carolina, and South Carolina) showed a blend of local and nonlocal (40%–60%) individuals. Finally, 15% of the southernmost population individuals (Puerto Rico) were classified as migratory, with some having a probability of origin at higher latitudes (>30°). Overall, our results provide evidence of a northward spring/summer migration of H. zea in North America and underscore the significance of the southeastern United States as a hub for genetic flow. In addition, based on stable hydrogen isotopic ratios, there is strong evidence of reverse (southward) migration of H. zea from the continental United States to Puerto Rico. Our study highlights the implications for IPM and IRM programs and the need for management strategies that account for both northward and southward migration patterns. [ABSTRACT FROM AUTHOR]

The first case of field-evolved resistance in European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) to transgenic corn (Zea mays L.) producing a Bacillus thuringiensis (Bt) Berliner toxin was discovered in Nova Scotia, Canada in 2018. This case involved resistance to Bt corn producing Cry1Fa toxin. As a mitigation response, Bt corn hybrids producing only Cry1Fa were replaced in that region with hybrids producing two or three Bt toxins targeting O. nubilalis. In this study, we collected O. nubilalis in several corn-growing regions of Canada during 2018 to 2020 and tested their progeny for susceptibility to four Bt toxins produced by currently available Bt corn that targets O. nubilalis : Cry1Fa, Cry1Ab, Cry1A.105, and Cry2Ab. Based on toxin concentrations killing 50% of larvae from 23 field-derived strains relative to two susceptible laboratory strains, the resistance ratio was at least 10 for Cry1Fa for 12 strains (52% of strains) consisting of 10 strains from Nova Scotia, as well as strains from near Montreal, Quebec and Roseisle, Manitoba. We found low but statistically significant resistance relative to at least one of two susceptible strains for Cry1Ab (23% of strains), Cry1A.105 (45% of strains), and Cry2Ab (14% of strains), with maximum resistance ratios of 3.9, 5.8, and 2.0, respectively. These results provide key information for addressing O. nubilalis resistance to Bt corn in Canada. [ABSTRACT FROM AUTHOR]

BACKGROUND: Striacosta albicosta Smith (Lepidoptera: Noctuidae) is a primary pest of corn, Zea mays L., in the Great Lakes region, causing yield loss and exacerbating mycotoxin contamination of grain. Foliar insecticides are currently used to manage S. albicosta; however, the toxicity and residual activity of these insecticides against S. albicosta are unknown. Laboratory and field bioassays were conducted to determine the susceptibility and period of in‐field efficacy provided by chlorantraniliprole, lambda‐cyhalothrin, spinetoram, and methoxyfenozide against S. albicosta. Bioassay data were used to simulate management scenarios. RESULTS: For all insecticides tested, 1st instars were highly susceptible to the recommended field application rates and were >3‐fold more susceptible to insecticides than 3rd instars. Insecticide activity decreased after application for all insecticides, with chlorantraniliprole having the longest residual activity. In simulated management scenarios where an insecticide was applied at or below the recommended 5% egg mass threshold with additional oviposition, methoxyfenozide application resulted in greater larval survival 14 days after application (DAA) than the other insecticides tested. In scenarios where insecticides were applied 7 days before threshold was reached, all insecticides resulted in larval survival. CONCLUSION: These data demonstrate that chlorantraniliprole, lambda‐cyhalothrin and spinetoram, applied in conjunction with monitoring, provide effective control of S. albicosta larvae for 10–14 days, whereas methoxyfenozide provides effective control for less than 7 days. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The phenology and voltinism of bean leaf beetle, Cerotoma trifurcata (Forster), were examined in three counties in 2010 and two counties in 2011 in Ontario soybean, Glycine max (L.) Merr. fields. Soil samples from within cages containing field-collected beetles revealed one cycle of eggs, larvae, and pupae. Observed degree-day (DD) accumulations for C. trifurcata life stage events (egg hatch, egg hatch to pupation, and oviposition to peak adult) in field experiments were compared with thermal constants determined in a temperature-dependent development laboratory experiment where C. trifurcata were reared under five constant temperatures. Observed and predicted DDs for all life stage events were nearly identical. Mean DD accumulations from first oviposition to peak adult emergence in the field studies was 589 ± 67 DD (base 10.3°C), which was nearly identical to the model prediction (581 ± 40 DD, base 10.3°C). [ABSTRACT FROM AUTHOR]

Four species of Limonius wireworms (Coleoptera: Elateridae), L. californicus, L. canus, L. infuscatus and L. agonus, are serious crop pests in North America. Limoniic acid, (E)-4-ethyloct-4-enoic acid, has been reported as a sex pheromone component of female L. californicus and L. canus, and a sex attractant for male L. infuscatus. In the same study, both limoniic acid and the analog (E)-5-ethyloct-4-enoic acid were highly attractive in field experiments. Moreover, six carboxylic acids in headspace volatiles of Limonius females elicited responses from male antennae but were not tested for behavioral activity. Here, we report trap catch data of Limonius spp. obtained in field experiments at 27 sites across North America. All four Limonius species were attracted to limoniic acid and to the analog but not to the carboxylic acids. Adding these carboxylic acids to limoniic acid, or to the analog, reduced its attractiveness. In dose–response studies, trap lures containing 0.4 mg or 4 mg of limoniic acid afforded large captures of L. californicus and L. infuscatus. Neither limoniic acid nor the analog were deterrent to other elaterid pest species. The broad attractiveness of limoniic acid to Limonius spp., and its non-deterrent effect on heterogeners, may facilitate the development of generic pheromone-based monitoring and management tools for multiple click beetle species. [ABSTRACT FROM AUTHOR]

Fusarium graminearum Schwabe (Hypocreales: Nectriaceae) and Fusarium verticillioides (Saccardo) (Hypocreales: Nectriaceae) Nirenberg infection results in accumulation of deoxynivalenol (DON), zearalenone (ZON), and fumonisin (FBs) mycotoxins in infected corn, Zea mays L. Lepidopteran insect feeding may exacerbate fungal infection by providing entry points on the ear resulting in increased mycotoxin contamination of grain. The objective of the current study was to simulate different types and severity levels (extent of injury) of lepidopteran injury to corn ears at different stages of ear development and its effect on mycotoxin accumulation in grain corn. Field experiments were conducted under conditions favorable for F. graminearum development where insect injury was simulated to corn ears and inoculated with F. graminearum. All simulated injury treatments resulted in elevated mycotoxin concentration compared with ears without simulated injury; however, the severity of injury within a treatment had little effect. Injury to kernels on the side of the ear resulted in greater DON and ZON concentration than injury to tip kernels, grazing injury applied at physiological maturity, or when no injury was simulated. Greater FBs was measured when tip kernel injury was simulated at the blister stage or when side kernel injury was simulated at milk and dent stages compared with noninjured ears, silk clipping, tip injury at milk and dent stages, or grazing injury at physiological maturity. The current study confirms that the risk of mycotoxin accumulation in the Great Lakes region is greater in the presence of ear-feeding insect pests and may differ depending on the feeding behavior of pest species. [ABSTRACT FROM AUTHOR]

A 4-yr study was conducted comparing the efficacy and value of fungicide-only (FST), neonicotinoid insecticide + fungicide (NST), and diamide insecticide + fungicide (DST) seed treatments for commercial corn Zea mays L. and soybean Glycines max (L.) Merr. production in Ontario, Canada. Plant stand, plant vigor, above- and below-ground insect injury, and yield were assessed on 160 field-scale experiments. Experiments also assessed early-season insect incidence and abundance using newly legislated thresholds for NST use in Ontario and in-season destructive sampling. Wireworms (Coleoptera: Elateridae) and white grubs (Coleoptera: Scarabeidae) were frequently observed at experimental sites; however, thresholds were rarely met and injury levels rarely led to yield loss. Of 129 and 31 corn and soybean sites, 8 and 6%, respectively, had a positive yield response to NST use. Across all sites, yield response of 0.1 and −0.05 Mg ha−1 was observed with NST use in corn and soybean, respectively; however, the costs associated with NST use were recovered at only 48 and 23% of corn and soybean sites, respectively, based on average grain prices and yields during the study. Infrequent incidence of economic injury and the absence of a consistent yield response to NST and DSTs throughout the 4 yr of the study indicate that widespread use of seed-applied insecticides in corn and soybean is unlikely to provide benefit to producers. These data highlight an opportunity for reducing input costs, environmental loading, and nontarget effects without adverse outcomes for Ontario producers. [ABSTRACT FROM AUTHOR]

Striacosta albicosta (Smith) (Lepidoptera: Noctuidae) is an important pest of corn, Zea mays L. in the Great Lakes region, which can be controlled by transgenic corn expressing Vip3A protein from Bacillus thuringiensis. To inform insect resistance management, the susceptibility, survival, and development of first, third, and fifth instar S. albicosta to Vip3A was determined using protein-overlay and corn tissue bioassays. Tissue bioassays were also used to determine the quantity of corn tissues with and without Vip3A-expression consumed by various instars. In diet bioassays, third and fifth instars were significantly less susceptible to Vip3A compared with first instars; however, no significant difference was observed in susceptibility of older instars. In tissue bioassays, survival was lowest for larvae fed Vip3A-expressing tissues, ranging from 0 to 21%, however, developmental measures of larvae fed Vip3A-expressing tissues did not differ from those fed artificial diet or tissues of other Bt events. Consumption of Vip3A × Cry1Ab tissues did not differ from that of Cry1Ab for each instar. Estimated Vip3A exposure of first instars ranged from 3 to 57 times higher than the concentration required for 99% mortality (LC99) based on the product of the reported Vip3A expression in transgenic corn tissues and the consumption observed in tissue bioassays; however, the estimated exposure of third and fifth instars to Vip3A was lower than their respective LC99. These findings suggest that first instar S. albicosta maybe exposed to a high dose of Vip3A under field conditions; however, Vip3A-expression in corn may not be high dose against older instars, increasing the risk of resistance development. [ABSTRACT FROM AUTHOR]

Neonicotinoids are widely used class of insecticides. Most are seed treatments and during planting active ingredient may be abraded and lost in fugitive dust. Much of this active ingredient contaminates surface waters, exposing aquatic organism to potential ill effects. This study examines concentrations of neonicotinoids appearing in tile drains and open ditches around commercial maize fields around planting time where neonicotinoid seed treatments had been used. This sample set represents surface water leaving the point of origin, for which data are sparse. Clothianidin was found more often than thiamethoxam and at higher concentrations; at a median concentration of 0.35 ng/mL in tile drain water and almost twice that (0.68 ng/mL) in ditches into which the tiles are draining after applications of 19 g/ha on seed. This concentration reveals a 40 to 50 fold dilution for neonicotinoid residues between the points where they leave the field in which they were applied and when they are found in nearby streams in a similar ecosystem. Our data support that for a no-observed-effect concentration of 0.3 ng/mL for thiamethoxam there would be between a 1.6 and 100-fold margin of safety to mayflies in most streams if fugitive dust on pneumatic planters were properly mitigated. [ABSTRACT FROM AUTHOR]

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is considered the most important maize (Zea mays L.) pest in the U.S. Corn Belt. Bioassays testing susceptibility to Bacillus thuringiensis Berliner (Bt) and other toxins of corn rootworm larvae often rely on artificial diet formulations. Successful bioassays on artificial diet for corn rootworm have sometimes been challenging because of microbial contamination. Toward the long-term goal of developing a universal artificial diet for western corn rootworm larvae, we compared larval survival, dry weight, and percentage of molt in 10-d bioassays from six current diets of which we were aware. In addition, as part of longer term rearing efforts, we recorded molting over an extended period of development (60 d). Six different artificial diets, including four proprietary industry diets (A, B, C, and D), the first published artificial diet for western corn rootworm (Pleau), and a new diet (WCRMO-1) were evaluated. Western corn rootworm larval survival was above 90% and contamination was 0% on all diets for 10 d. Diet D resulted in the greatest dry weight and percentage molting when compared with the other diets. Although fourth-instar western corn rootworm larvae have not been documented previously (only three instars have been previously documented), as many as 10% of the larvae from Diet B molted into a fourth instar prior to pupating. Overall, significant differences were found among artificial diets currently used to screen western corn rootworm. In order for data from differing toxins to be compared, a single, reliable and high-quality western corn rootworm artificial diet should eventually be chosen by industry, academia, and the public as a standard for bioassays. [ABSTRACT FROM AUTHOR]

Striacosta albicosta (Smith; Lepidoptera: Noctuidae) is a pest of corn (Zea mays L.), which has recently expanded its range into Ontario, Canada. Genetically modified corn expressing Vip3A insecticidal protein from Bacillus thuringiensis is a biotechnological option for the control of S. albicosta. To support an insect resistance management program, we conducted a study of baseline susceptibility of 10-field collected S. albicosta populations in Ontario, Canada to Vip3A before widespread commercial adoption. Neonates were exposed to artificial diet overlaid with Vip3A. The LC50 ranged from 22.7 to 53.5 ng Vip3A cm-2. The EC50 ranged from 11.4 to 30.2 ng Vip3A cm-2. There was low inter-population variation in susceptibility to Vip3A, which we believe represents the natural geographical variation in response and not variation caused by previous exposure to selection pressure of the Vip3A protein. [ABSTRACT FROM AUTHOR]

Soybean aphid is a severe invasive pest of soybeans in North America. From 2005 onward, a network of 47 suction traps in North America, each approximately 7 m in height, has monitored aerial populations of this species., Suction trap captures of alate viviparous Aphis glycines in summer, and gynoparae and males in the autumn, were subjected to negative binomial regressions with environmental parameters. Models were ranked by using information-theoretic methods to determine which parameters best explained aerial density of aphids. Multiparameter models incorporating the best parameters were constructed., Best-fit models were used to compute peak values of each parameter, where a quadratic relationship between captures and that parameter occurred. Data were subjected to non-metric multidimensional scaling and analysis of similarity to observe patterns in the geographical and temporal distribution of captures., Summer flight activity A. glycines was explained best by the level of aphid infestation in fields local to the trapping site, although the autumn female flight activity peak and male activity was best explained by photoperiod., Seven-metre tall suction traps are useful for determining when flight activity of A. glycines occurs within a region. [ABSTRACT FROM AUTHOR]

The western bean cutworm, Striacosta albicosta (Smith) is a native North American pest of corn and dry beans. The historical geographic range of the western bean cutworm covered the western Great Plains states including Colorado, Nebraska, and Wyoming. Since 1999, the geographic range of the western bean cutworm has rapidly expanded eastward across the U.S. Corn Belt and eastern Canada, causing significant and economic damage to corn Zea mays (L.) and dry edible beans Phaseolus spp. in parts of this region. Since 2010, increasing challenges related to managing this pest in its new range prompted numerous research studies that provided new insights into the biology and management of western bean cutworm. This revision of a previous Journal of IPM profile summarizes new information regarding the ecology and biology of western bean cutworm, and discusses updated recommendations for scouting and management in corn and dry beans, with an emphasis in the expanded geographic range of the Great Lakes region. [ABSTRACT FROM AUTHOR]