The western corn rootworm, Diabrotica virgifera virgifera LeConte, is the primary insect pest threatening corn, Zea mays L., production in many areas of the United States and is capable of inflicting substantial yield loss. In Illinois and bordering states, managing this pest is complicated by populations exhibiting resistance to crop rotation, historically an effective strategy to prevent larval injury caused by this corn specialist. Rotation resistance is characterized by ovipositional infidelity to corn accompanied by various adaptations promoting prolonged residency in soybean, Glycine max (L.) Merr. We conducted an analysis using survey data to estimate densities of western corn rootworm adults in Illinois soybean fields and compared those estimates for two discrete time periods: (1) 1997–2003 and (2) 2011 and 2013–2015. Annual surveys during each time period were conducted from late July through late August by visiting a number of randomly selected soybean fields in counties distributed throughout Illinois. Adults were sampled using sweep nets. Mean densities were determined for each United States Department of Agriculture crop reporting district and interpolated values were estimated to produce statewide contour plots. Our findings reveal a substantial decline in adult abundance in soybean fields throughout much of Illinois. Where significant differences were observed between the two survey periods, recent densities were 88% lower on average than those observed during 1997–2003. Potential factors contributing to the declines we observed and implications for managing this adaptive pest of corn are discussed.

We established two trials near DeKalb and Urbana, IL. The experimental design for each trial was an RCB with four replications. Plot size was 10 ft (four rows) by 40 ft. Trials were planted on 8 and 12 May at DeKalb and Urbana, respectively. Trials were planted using a four-row, vacuum style planter constructed by Seed Research Equipment Solutions (South Hutchinson, KS). The previous crop at each location was a trap crop (late-planted corn and pumpkins). Seeds were planted at a rate of 36,600 seeds/acre in 30-inch rows at an approximate depth of 1.75 inch. Granular insecticides were applied through modified Noble metering units mounted to each row. Plastic tubes directed the insecticide granules into the seed furrow. Liquid insecticides were applied at a spray …

Seed blends containing various ratios of transgenic Bt maize (Zea mays L.) expressing the mCry3A + eCry3.1Ab proteins and non-Bt maize (near-isoline maize) were deployed alone and in combination with a soil applied pyrethroid insecticide (Force CS) to evaluate the emergence of the western corn rootworm, Diabrotica virgifera virgifera LeConte, in a total of nine field environments across the Midwestern United States in 2010 and 2011. Northern corn rootworm, Diabrotica barberi Smith & Lawrence emergence was also evaluated in four of these environments. Both western and northern corn rootworm beetle emergence from all Bt treatments was significantly reduced when compared with beetle emergence from near-isoline treatments. Averaged across all environments, western corn rootworm beetle emergence from 95:5, 90:10, and 80:20 seed blend ratios of mCry3A + eCry3.1Ab: near-isoline were 2.6-, 4.2-, and 6.7-fold greater than that from the 100:0 ratio treatment. Northern corn rootworm emergence from the same seed blend treatments resulted in 2.8-, 3.2-, and 4.2-fold more beetles than from the 100:0 treatment. The addition of Force CS (tefluthrin) significantly reduced western corn rootworm beetle emergence for each of the three treatments to which it was applied. Force CS also significantly delayed the number of days to 50% beetle emergence in western corn rootworms. Time to 50% beetle emergence in the 100% mCry3A + eCry3.1Ab treatment with Force CS was delayed 13.7 d when compared with western corn rootworm beetle emergence on near-isoline corn. These data are discussed in terms of rootworm resistance management.

We established one trial at the Northwestern Illinois Agricultural Research and Development Center near Monmouth, IL, to evaluate the efficacy of soil-applied insecticides and Bt hybrids to control corn rootworm (CRW) larvae. The experimental design was a RCB with four replications. The plot size for each treatment was 10 ft (four rows) × 40 ft. The previous crop was a trap-crop (late-planted corn and pumpkins). Corn was planted on 7 May using a four-row, vacuum-style planter (SRES, South Hutchinson, KS) at a rate of 36,600 seeds/acre in 30-inch rows at an approximate depth of 1.75 inches. Hybrid information is provided in Table 1. Granular insecticides were applied through modified Noble metering units or through modified SmartBox metering …

We established one trial at the Northern Illinois Agronomy Research Center near DeKalb, IL, to evaluate the efficacy of soil-applied insecticides to control CRW larvae. The experimental design was a RCB with four replications. The plot size for each treatment was 10 ft (four rows) by 40 ft. The previous crop was a trap-crop (late-planted corn and pumpkins). The trial was planted on 8 May using a four-row, vacuum-style planter (SRES, South Hutchinson, KS). Seeds were planted at a rate of 38,500 seeds/acre in …

We established one trial near Morrison, IL, to evaluate the efficacy of foliar-applied insecticides and insecticide/fungicide combinations to control Japanese beetles. The experimental design was an RCB with four replications. The plot size for each treatment was 10 ft (four rows) × 20 ft. The trial was planted on 23 May using a 16-row, Case IH Model 1240 Early Riser planter. Seeds were planted at a rate of 155,600 seeds/acre in 30-inch rows at an approximate depth of …

We established one trial at the Northern Illinois Agronomy Research Center near DeKalb, IL, to evaluate the efficacy of Warrior II and Warrior II + Quilt Xcel to control insect pests of soybean.The experimental design was a RCB with four replications.The plot size for each treatment was 20 ft (eight rows) x 100 ft.The trial was planted on 11 Jun using a 4-row, John Deere 7300 planter.Seeds were planted at a population of 150,000 seeds/acre in 30-in rows at an approximate depth of 1 inch.The variety used for the trial was NK S31-L7.Insecticides and fungicides were applied on 8 Aug with a CO 2powered backpack sprayer and a four-row boom.TeeJet TTJ60-11002 spray tips were calibrated to deliver a volume of 20 gpa.Densities of corn rootworm beetles were determined by taking 20 sweeps per plot with a 15-inch diameter sweep net.Densities of soybean aphids were determined by counting the total number of aphids on three plants in each plot.Densities of corn rootworm beetles were assessed on 8, 15, 22, and 29 Aug (0, 7, 14, and 21 DAT, respectively).Populations of soybean aphids were not detectable until late Aug; because of this, aphid densities were not evaluated until 22 Aug (14 DAT).Yields were estimated by harvesting the center two rows of each plot on 29 Oct. Weights were converted to bu/acre at 13% moisture.Data were analyzed using ARM 8, revision 8.5.

We established a trial at the Northern Illinois Agronomy Research Center near DeKalb, IL, to evaluate the efficacy of foliar-applied insecticides to control insect pests of soybean. The experimental design was a RCB with four replications. The plot size for each treatment was 10 ft (four rows) x 20 ft. The trial was planted on 11 Jun using a 4-row, John Deere 7300 planter. Seeds were planted at a population of 150,000 seeds/acre in 30-inch rows at an approximate depth of 1 inch. The variety used for the trial was NK S31-L7. Insecticides and fungicides were applied on 8 Aug with a CO2-powered backpack sprayer and a four-row boom. TeeJet TTJ60-11002 spray tips were calibrated to deliver a volume of 20 gpa. Densities of corn rootworm beetles were determined by taking 20 sweeps per plot with a 15-inch diameter sweep net. Densities of soybean aphids were determined by counting the total number of aphids on three plants in each plot. Densities of corn rootworm beetles were assessed on 8, 15, 22, and 29 Aug (0, 7, 14, and 21 DAT, respectively). Populations of soybean aphids were not detectable until late Aug; because of this, aphid densities were not evaluated until 22 Aug (14 DAT). Yields were estimated by harvesting the center two rows of each plot on 29 Oct. Weights were converted to bu/acre at 13% moisture. Data were analyzed using ARM 8, revision 8.5.0 (Gylling Data Management, Inc., Brookings, SD).

The refuge strategy can delay resistance of insect pests to transgenic maize producing toxins from Bacillus thuringiensis (Bt). This is important for the western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), because of its history of adaptation to several management practices. A 2-yr study across four locations was conducted to measure the effects of integrated refuge (i.e., blended refuge) on western corn rootworm survival to adulthood, fitness characteristics, and susceptibility to Bt maize in the subsequent generation. The treatments tested in this study were as follows: a pure stand of Bt maize (event DAS-59122-7, which produces Bt toxins Cry34Ab1/Cry35Ab1), a pure stand of refuge (non-Bt maize), and two variations on an integrated refuge consisting of 94.4% Bt maize and 5.6% non-Bt maize. Within the two integrated refuge treatments, refuge seeds received a neonicotinoid insecticidal seed treatment of either 1.25 mg clothianidin per kernel or 0.25 mg thiamethoxam per kernel. Insects in the pure stand refuge treatment had greater survival to adulthood and earlier emergence than in all other treatments. Although fecundity, longevity, and head capsule width were reduced in treatments containing Bt maize for some site by year combinations, Bt maize did not have a significant effect on these factors when testing data across all sites and years. We found no differences in susceptibility of larval progeny to Bt maize in bioassays using progeny of adults collected from the four treatments.

Diabrotica virgifera virgifera LeConte

Transgenic Bt corn hybrids that produce insecticidal proteins from the bacterium Bacillus thuringiensis Berliner have become the standard insect management tactic across the U.S. Corn Belt. Widespread planting of Bt corn places intense selection pressure on target insects to develop resistance, and evolution of resistance threatens to erode benefits associated with Bt corn, such as reduced reliance on conventional insecticides. Recognizing the threat of resistance, the U.S. Environmental Protection Agency requires seed companies to include an insect resistance management (IRM) plan when registering a Bt trait. The goal of IRM plans is to delay Bt resistance in populations of target insects. One element of IRM is the presence of a non-Bt refuge to maintain Bt-susceptible individuals within a population, and growers are required to implement IRM on-farm by planting a refuge. Field-evolved resistance has not been detected for the European corn borer, Ostrinia nubilalis (Hubner), even though this species has been exposed to Bt proteins common in U.S. corn hybrids since 1996. The IRM situation is unfolding differently for Bt corn targeting the western corn rootworm, Diabrotica virgifera virgifera LeConte. In this article, we examine the scientific evidence for D. v. virgifera resistance to Bt rootworm traits and the cropping system practices that have contributed to the first reports of field-evolved resistance to a Bt toxin by D. v. virgifera . We explain why this issue has developed, and emphasize the necessity of an integrated pest management approach to address the issue.

During a multistate survey (2009) of diseases of perennial grasses under consideration as biofuel feedstocks, a new leaf blight of Miscanthus × giganteus caused by Leptosphaerulina chartarum was observed on 100 % of the plants evaluated in research plots near Lexington, Kentucky. A greenhouse study was conducted to evaluate the effect of L. chartarum on M. × giganteus biomass and to identify effective foliar fungicides against the disease. Eleven broad-spectrum fungicides were tested with rates typically used in agronomic crops. Fungicides tested included active ingredients from five different chemical groups, demethylation inhibitors (prothioconazole, tebuconazole, cyproconazole, propiconazole, tetraconazole, flutriafol, and metconazole), quinone outside inhibitors (pyraclostrobin), succinate dehydrogenase inhibitors (boscalid), methyl benzimidazole carbamates (thiophanate-methyl), and chloronitriles (chlorothalonil). Infection by L. chartarum significantly lowered aboveground biomass by an average of 33 %. Application of cyproconazole, flutriafol, tebuconazole, or prothioconazole significantly reduced disease severity, with cyproconazole and flutriafol ranking best at an average of 29 % disease control. However, no fungicide treatment resulted in biomass loss abatement. Greater rates or a combination of fungicides might be needed to achieve adequate control.