Unequal burdens of loss: examining the frequency and timing of homicide deaths experienced by young Black men across the life course.

OBJECTIVES: I examined the frequency and developmental timing of traumatic loss resulting from the health disparity of homicide among young Black men in Baltimore, Maryland. METHODS: Using a modified grounded theory approach, I conducted in-depth semistructured interviews with 40 Black men (aged 18-24 years) from January 2012 to June 2013. I also constructed adapted life history calendar tools using chronologies of loss, and (1) provided a comprehensive history of loss, (2) determined a specific frequency of homicide deaths, (3) indicated participants' relationship to the decedents, and (4) identified the developmental timing of deaths. RESULTS: On average, participants knew 3 homicide victims who were overwhelmingly peers. Participant experiences of homicide death started in early childhood, peaked in adolescence, and persisted into emerging adulthood. The traumatic loss of peer homicide was a significant developmental turning point and disrupted participants' social networks. CONCLUSIONS: The traumatic loss of peer homicide was a prevalent life course experience for young Black men and identified the need for trauma- and grief-informed interventions. Future research is needed to examine the physical and psychosocial consequences, coping resources and strategies, and developmental implications of traumatic loss for young Black men in urban contexts.

Quantifying Neonicotinoid Insecticide Residues Escaping during Maize Planting with Vacuum Planters.

Neonicotinoid residues escaping in vacuum-planter exhaust during maize planting were measured in 25 fields in southwestern Ontario in 2013-2014 using filter bags to collect planter exhaust dust and horizontal and vertical sticky traps to collect planter operation-generated dust. Atrazine residues were used to differentiate between neonicotinoid residues originating from seed or from disturbed soil. Recovery rates of seed-applied neonicotinoids in exhaust were 0.014 and 0.365% in 2013 and 2014, respectively, calculated on the basis of neonicotinoid concentrations in preplant soil and seed application rates. Neonicotinoid exhaust emission rates were 0.0036 and 0.1104 g/ha for 2013 and 2014, respectively, with 99.9472 and 99.7820% originating from treated seed in 2013 and 2014, respectively, calculated on the basis of the atrazine marker. Rates of recovery of seed-applied neonicotinoid residues by exhaust filter bags were 0.015 and 0.437% for 2013 and 2014, respectively. Neonicotinoid residues captured on horizontal and vertical traps were 1.10 ng/cm2 (0.1104 g/ha) and 1.45 ng/cm2 (0.0029 g/ha), respectively, with 92.31 and 93.03% originating from treated seed, respectively, representing 0.3896% of the original active ingredient applied to the seed planted. Exposure to pollinators can be best reduced by strategies to keep active ingredient on the seed, below the soil surface, and in the field where applied.

Growing up as "man of the house": adultification and transition into adulthood for young men in economically disadvantaged families.

Many children in economically disadvantaged communities assume adult roles in their families. Negotiating the responsibilities and expectations associated with becoming what some young men describe as "man of the house" has important implications for how adolescent boys move into adulthood. In this study, we share insights from field work and life-history interviews with low-income, young African American men and Salvadoran men in the Washington, DC/Baltimore region to illustrate how adultification may deliver contradictory expectations for adolescents. The findings also show how the accelerated responsibilities that accompany the experience of adultification create difficulties in the young men's transition into adulthood. These findings indicate that the age period of emerging adulthood may begin earlier for economically disadvantaged young men.

Wireworm species associated with corn and soybean agroecosystems in Ontario, Canada.

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.

Continental-scale migration patterns and origin of Helicoverpa zea (Lepidoptera: Noctuidae) based on a biogeochemical marker.

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.

Monitoring resistance of Ostrinia nubilalis (Lepidoptera: Crambidae) in Canada to Cry toxins produced by Bt corn.

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.

Genetic mutations linked to field-evolved Cry1Fa-resistance in the European corn borer, Ostrinia nubilalis.

Transgenic corn, Zea mays (L.), expressing insecticidal toxins such as Cry1Fa, from Bacillus thuringiensis (Bt corn) targeting Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) resulted in over 20 years of management success. The first case of practical field-evolved resistance by O. nubilalis to a Bt corn toxin, Cry1Fa, was discovered in Nova Scotia, Canada, in 2018. Laboratory-derived Cry1Fa-resistance by O. nubilalis was linked to a genome region encoding the ATP Binding Cassette subfamily C2 (ABCC2) gene; however, the involvement of ABCC2 and specific mutations in the gene leading to resistance remain unknown. Using a classical candidate gene approach, we report on O. nubilalis ABCC2 gene mutations linked to laboratory-derived and field-evolved Cry1Fa-resistance. Using these mutations, a DNA-based genotyping assay was developed to test for the presence of the Cry1Fa-resistance alleles in O. nubilalis strains collected in Canada. Screening data provide strong evidence that field-evolved Cry1Fa-resistance in O. nubilalis maps to the ABCC2 gene and demonstrates the utility of this assay for detecting the Cry1Fa resistance allele in O. nubilalis. This study is the first to describe mutations linked to Bt resistance in O. nubilalis and provides a DNA-based detection method that can be used for monitoring.

Extended Sentinel Monitoring of Helicoverpa zea Resistance to Cry and Vip3Aa Toxins in Bt Sweet Corn: Assessing Changes in Phenotypic and Allele Frequencies of Resistance.

Transgenic corn and cotton that produce Cry and Vip3Aa toxins derived from Bacillus thuringiensis (Bt) are widely planted in the United States to control lepidopteran pests. The sustainability of these Bt crops is threatened because the corn earworm/bollworm, Helicoverpa zea (Boddie), is evolving a resistance to these toxins. Using Bt sweet corn as a sentinel plant to monitor the evolution of resistance, collaborators established 146 trials in twenty-five states and five Canadian provinces during 2020-2022. The study evaluated overall changes in the phenotypic frequency of resistance (the ratio of larval densities in Bt ears relative to densities in non-Bt ears) in H. zea populations and the range of resistance allele frequencies for Cry1Ab and Vip3Aa. The results revealed a widespread resistance to Cry1Ab, Cry2Ab2, and Cry1A.105 Cry toxins, with higher numbers of larvae surviving in Bt ears than in non-Bt ears at many trial locations. Depending on assumptions about the inheritance of resistance, allele frequencies for Cry1Ab ranged from 0.465 (dominant resistance) to 0.995 (recessive resistance). Although Vip3Aa provided high control efficacy against H. zea, the results show a notable increase in ear damage and a number of surviving older larvae, particularly at southern locations. Assuming recessive resistance, the estimated resistance allele frequencies for Vip3Aa ranged from 0.115 in the Gulf states to 0.032 at more northern locations. These findings indicate that better resistance management practices are urgently needed to sustain efficacy the of corn and cotton that produce Vip3Aa.

Susceptibility and field exposure of Striacosta albicosta (Lepidoptera: Noctuidae) eggs and larvae in Ontario, Canada to four insecticides.

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.

Phenology of Bean Leaf Beetle (Coleoptera: Chrysomelidae) in Ontario, Canada and Field Validation of a Degree-Day Model.

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).

Best Management Practices to Delay the Evolution of Bt Resistance in Lepidopteran Pests Without High Susceptibility to Bt Toxins in North America.

Canadian and United States (US) insect resistance management (IRM) programs for lepidopteran pests in Bacillus thuriengiensis (Bt)-expressing crops are optimally designed for Ostrinia nubilalis Hübner in corn (Zea mays L.) and Chloridea virescens Fabricius in cotton (Gossypium hirsutum L.). Both Bt corn and cotton express a high dose for these pests; however, there are many other target pests for which Bt crops do not express high doses (commonly referred to as nonhigh dose pests). Two important lepidopteran nonhigh dose (low susceptibility) pests are Helicoverpa zea Boddie (Lepidoptera: Noctuidae) and Striacosta albicosta Smith (Lepidoptera: Noctuidae). We highlight both pests as cautionary examples of exposure to nonhigh dose levels of Bt toxins when the IRM plan was not followed. Moreover, IRM practices to delay Bt resistance that are designed for these two ecologically challenging and important pests should apply to species that are more susceptible to Bt toxins. The purpose of this article is to propose five best management practices to delay the evolution of Bt resistance in lepidopteran pests with low susceptibility to Bt toxins in Canada and the US: 1) better understand resistance potential before commercialization, 2) strengthen IRM based on regional pest pressure by restricting Bt usage where it is of little benefit, 3) require and incentivize planting of structured corn refuge everywhere for single toxin cultivars and in the southern US for pyramids, 4) integrate field and laboratory resistance monitoring programs, and 5) effectively use unexpected injury thresholds.

Limoniic Acid and Its Analog as Trap Lures for Pest Limonius Species (Coleoptera: Elateridae) in North America.

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.

Quantifying Early-Season Pest Injury and Yield Protection of Insecticide Seed Treatments in Corn and Soybean Production in Ontario, Canada.

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.

The Effect of Simulated Lepidopteran Ear Feeding Injury on Mycotoxin Accumulation in Grain Corn (Poales: Poaceae).

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.

Practical Resistance of Ostrinia nubilalis (Lepidoptera: Crambidae) to Cry1F Bacillus thuringiensis maize discovered in Nova Scotia, Canada.

Transgenic maize, Zea mays L., modified to express insecticidal proteins from the bacterium Bacillus thuringiensis Berliner, was introduced in 1996 to control Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), a key maize pest in North America. The high-dose/refuge concept, developed to delay or prevent resistance evolution to this technology, has been exemplified by O. nubilalis as no cases of practical resistance were identified in >20 years. This study documents the first case of practical resistance to Cry1F Bt maize by O. nubilalis in North America. Four collections of O. nubilalis were made from Cry1F maize in Nova Scotia, Canada with unexpected injury (UXI) ranging from 30-70%. Greater survival of UXI collections was observed when larvae were exposed to the highest concentration of 200 ng Cry1F cm-2 in diet-overlay bioassays compared to susceptible laboratory colonies. Larvae also fed and survived on Cry1F leaf tissue in 7 d bioassays. A collection from non-Bt maize, 120 km west of the UXI region, also survived 200 ng Cry1F cm-2, but was susceptible to Cry1F leaf tissue. Detection of Cry1F-resistant O. nubilalis in what might be considered an insignificant maize-growing region indicates that a number of preventable causal factors may have been related to inadequate stewardship of Bt maize technology.

Susceptibility of Different Instars of Striacosta albicosta (Lepidoptera: Noctuidae) to Vip3A, a Bacillus thuringiensis (Bacillaceae: Bacillales) Protein.

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.

Neonicotinoid insecticide residues in subsurface drainage and open ditch water around maize fields in southwestern Ontario.

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.

Baseline Susceptibility of Striacosta albicosta (Lepidoptera: Noctuidae) in Ontario, Canada to Vip3A Bacillus thuringiensis Protein.

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.

Fusarium graminearum Mycotoxins in Maize Associated With Striacosta albicosta (Lepidoptera: Noctuidae) Injury.

Western bean cutworm, Striacosta albicosta (Smith; Lepidoptera: Noctuidae) has become a key pest of maize, Zea mays (L.), in Ontario, Canada which is challenging to control due to its lack of susceptibility to most Bt-maize events. Injury by S. albicosta may exacerbate Fusarium graminearum (Schwabe; Hypocreales: Nectriaceae) infection through provision of entry points on the ear. The objectives of this study were to: investigate the relationship between injury by S. albicosta and deoxynivalenol (DON) accumulation; evaluate non-Bt and Bt-maize hybrids, with and without insecticide and fungicide application; and determine optimal insecticide-fungicide application timing for reducing S. albicosta injury and DON accumulation. The incidence of injury by S. albicosta and ear rot severity were found to increase DON concentrations under favorable environmental conditions for F. graminearum infection. Incidence of S. albicosta injury was more important than severity of injury for DON accumulation which may be due to larval consumption of infected kernels. The Vip3A × Cry1Ab event provided superior protection from the incidence and severity of S. albicosta injury compared to non-Bt or Cry1F hybrids. Insecticide application to a Vip3A × Cry1Ab hybrid did not reduce injury further; however, lower severity of injury was observed for non-Bt and Cry1F hybrids when pyrethroids or diamides were applied at early VT or R1 stages. DON concentrations were reduced with application of prothioconazole fungicide tank-mixed with insecticide at late VT (before silk browning) or when insecticide was applied at early VT followed by prothioconazole at R1. The application of an insecticide/fungicide tank-mix is the most efficient approach for maize hybrids lacking high-dose insecticidal proteins against S. albicosta and F. graminearum tolerance. Results demonstrate that reducing the risk of DON accumulation requires a strategic approach to manage complex associations among S. albicosta, F. graminearum and the environment.

Comparison of Six Artificial Diets for Western Corn Rootworm Bioassays and Rearing.

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.