[Show abstract][Hide abstract] ABSTRACT: Impacts of semiochemical-based insecticidal bait applications on beneficial arthropod groups common to field corn, Zea mays L., habitats were assessed in areawide-managed field sites in South Dakota and Iowa during 1997 and 1998. Slam, a commercial bait formulation comprised of 87% cucurbitacin and 13% carbaryl insecticide, was used for management of adult rootworm, Diabrotica spp., and controls consisted of cornfield habitats without bait applications. Effects on beneficial organisms were variable, and negative impacts were infrequent. Coccinellidae, Staphylinidae, and Anthocoridae were usually more abundant in bait-treated plots than in controls that received at-plant soil insecticides, especially by 4 wk postapplication. Carabid beetle activity also had increased in bait-treated corn by proportionally greater rates than in control plots at 4 wk postapplication in two of the four site by year combinations in this study. Impacts of semiochemical-based adulticide applications on Formicidae were not consistently negative or positive. The relative lack of consistent negative impacts on nontarget arthropods suggests that other biotic and abiotic factors leading to natural population fluxes may have more influence on these groups of beneficial organisms than applications of semiochemical-based bait containing carbaryl. Overall, it seems that areawide applications of these baits for managing rootworm populations in corn are not likely to impose deleterious effects on the nontarget faunal groups we surveyed, especially in comparison with the at-plant applications of soil insecticides used as experimental controls in this study.
Journal of Economic Entomology 01/2006; 98(6):1957-68. · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Lady beetles (Coleoptera: Coccinellidae) are important polyphagous predators in maize, Zea mays L., fields. Transgenic Cry3Bb1 maize hybrids express a coleopteran-specific insecticidal protein derived from Bacillus thuringiensis (Berliner) subsp. kumamotoensis that is targeted at corn rootworm larvae. This study evaluated impacts of Cry3Bb1 protein-expressing maize, tefluthrin-treated maize, and untreated controls on lady beetle abundance at preanthesis, anthesis, and postanthesis maize-developmental periods near Brookings in eastern South Dakota during 2001 and 2002. The dominant lady beetle species captured on Pherocon AM sticky traps was Coleomegilla maculata De Geer. It comprised 73.5 and 69.9% of all adult Coccinellidae caught in 2001 and 2002, respectively. Numbers of C. maculata captured in Cry3Bb1 maize were not significantly different from those in untreated plots during preanthesis, and adults were more abundant in Cry3Bb1 maize than in tefluthrin-treated and untreated plots during anthesis and postanthesis. Whole-plant sampling confirmed C. maculata predominance with the species representing 89.2 and 91.4% of all adult lady beetles observed in 2001 and 2002, respectively. Whole-plant sampling also indicated a lack of negative effects from Cry3Bb1 maize on abundance of lady beetle eggs, larvae, pupae, or adults. Overall, these findings indicate that Cry3Bb1-expressing hybrids are not likely to impose harmful effects on C. maculata, a species common to maize production systems in the northern Great Plains. This research further suggests that Cry3Bb1 maize has the potential for conservation of these beneficial coccinellids in maize production systems.
Journal of Economic Entomology 01/2006; 98(6):1992-8. · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ground beetles often prey on crop pests, and their relative abundance and assemblages vary among cropping systems and pest management practices. We used pitfall traps arranged in transects to study ground beetle assemblages in a large field-scale Bt corn¡soybean cropping system for 3 yr. The transgenic corn expressed the Cry1Ab protein targeting lepidopteran pests. Three of the 57 ground beetle species collected accounted for 81% of all individuals captured. Six other species accounted for an additional 14% of all beetles captured. Ground beetles were captured equally in cornfields and soybean fields. They also were captured most frequently at field edges, but many were captured within field centers. Canonical correspondence analysis was used to arrange ground beetles along environmental gradients. Years 2001 and 2002 were the primary variables separating assemblages of ground beetles along the first canonical axis. The second canonical axis further separated the 2000 assemblage of ground beetles. With the effects of year and field removed, ground beetles were classified with respect to crop association and distance into the fields along axes 1 and 2 of a partial canonical correspondence analysis. Based on this analysis, ground beetles occupying the Bt cornfields were separated from those occupying soybean fields along the first canonical axis. The second canonical axis separated beetles occupying the field borders from field interiors. Ground beetles ordinating near the center of the axes may represent habitat generalists, and because of their high relative abundances, continuous seasonal activity, predatory nature, and ability to occupy field centers, they could assist in the biological control of agricultural pests.
[Show abstract][Hide abstract] ABSTRACT: A 3-yr investigation was conducted in commercial corn, Zea mays (L.), fields in eastern South Dakota to determine how reduced application rates of planting-time soil insecticides would influence temporal emergence patterns and survival of northern and western corn rootworms, Diabrotica barberi Smith and Lawrence, and D. virgifera virgifera LeConte, respectively. Beetle emergence was monitored at 2-d intervals throughout the entire adult emergence period of three growing seasons from corn plots treated with planting-time applications of labeled (1X) and reduced (0.5 and 0.75X) application rates of terbufos, tefluthrin, and chlorethoxyfos. No consistent insecticide- or rate-related impacts on mean total emergence per trap were recorded for any of the compounds investigated. However, terbufos applications resulted in a 52% reduction in the number of beetles captured per trap, 53% reduction in maximum rate of adult emergence, and a 59% reduction in overall rate of emergence over time for male D. virgifera during 1994. Terbufos also significantly extended the time required for emergence to peak and linear emergence of female D. virgifera to end in 1994. Tefluthrin applications delayed onset, end, and time of maximum emergence of female D. barberi by 9.9, 14.1, and 12 d, respectively, during 1993. Tefluthrin also reduced emergence rates over time for male (38%) and female (46%) D. barberi during 1994. Overall, application rate was inconsequential regarding total emergence, seasonal emergence pattern, or level of plant protection provided for all insecticides we tested in this 3-yr investigation. Our findings demonstrate that, if properly applied, the reduced application rates used in this study provide adequate root protection and will not significantly impact the biology of these pest species.
Journal of Economic Entomology 07/2003; 96(3):714-29. · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Arthropod abundance on mixed-grass rangeland was determined before and after spray treatments for grasshopper suppression. These evaluations were made in field plots (16.2 ha) treated with either Beauveria bassiana (Balsamo) Vuillemin strain GHA at 1 × 1013 conidia in 1.89 liter oil per 0.405 ha, carbaryl at 559.88 g (AI) in 0.59 liter total volume per hectare, or no insecticide (untreated controls). Infectivity of B. bassiana was determined by capturing grasshoppers from treatment plots 7 d after application and monitoring them for external growth of the fungus. Major predators, parasitoids, and pollinators were captured with pitfall and malaise traps weekly throughout the summer season. About one-half of the grasshoppers collected from B. bassiana treatment plots exhibited external growth of the fungus. Formicidae, Araneae, and Carabidae decreased in all plots during periods of heavy precipitation after the treatment date, but these declines were not caused by mortality as a result of B. bassiana or carbaryl spray treatments. Ground-dwelling arthropod abundance rebounded to pretreatment levels ≈2 wk after treatments. No statistical differences in the abundance of aerial insects were detected with respect to treatment effects; however, natural increases in abundance in all plots were observed as the season progressed.
[Show abstract][Hide abstract] ABSTRACT: The influence of soil insecticide application rates on the reproductive biologies of field-collected northern and western corn rootworms, Diabrotica barberi Smith & Lawrence, and D. virgifera virgifera LeConte, respectively, was investigated under laboratory conditions. Comparisons were made on beetles obtained from plots treated with planting-time applications of labeled (IX) and reduced (0.5 and 0.75X) rates of chlorethoxyfos, tefluthrin, and terbufos, and from untreated control plots. Captured insects were pooled by species and insecticide treatment into laboratory rearing cages and allowed to mate. Gravid females were held individually in oviposition chambers to assess fecundity. Egg viability was measured on subsamples of eggs from all treatments. No significant differences (P >0.05) were detected in fecundity, fertility, or percentage of nonviable eggs of D. barberi or D. virgifera with any insecticide or application rate within insecticide tested. However, reductions in total eggs produced and hatch were 31.2 and 53.7%, respectively, for D. virgifera that survived chlorethoxyfos treatment in comparison with beetles that emerged from untreated plots. Also, the percentage of nonviable eggs produced by D. virgifera emerging from chlorethoxyfos-treated plots was 2-fold of that in beetles captured from untreated corn plots. Whereas, D. barberi females from tefluthrin-treated plots experienced a 44% increase in fecundity and 49.2% more egg hatch than those from the untreated controls. Additionally, total eggs and hatch were increased by 32.1 and 33.7%, respectively, in D. barberi that emerged from terbufos-treated corn plots when compared with their counterparts from untreated control plots. The numerical disparities that we observed appeared to be species specific rather than associated with insecticide class or application rate. Our evaluations indicate that using reduced (0.5 and O.75X) application rates of these organophosphate and pyrethroid insecticides will not likely have major effects on the reproductive capacities of D. barberi or D. virgifera. Thus, corn rootworm management programs should include options for using the lowest efficacious application rates of these insecticides.
Journal of Economic Entomology 01/1998; 91(1):274-279. · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Seasonal emergence time was studied to determine its influence on adult vigor and reproductive fitness of field-collected Diabrotica barberi Smith & Lawrence and D. virgifera virgifera LeConte. Time of emergence was divided into six 2-wk intervals (lots; pooled from beetles collected every 2 d from onset to end of seasonal emergence cycle), which served as treatments. Beetles were maintained in single-insect oviposition chambers on a natural diet and were provided soil as an oviposition substrate. The experiment was arranged in a randomized complete block design with 10 replicates. Female D. barberi survived on natural diet for averages of up to 89 d within lots. Earliest emerging (lot 1) beetles of both species lived significantly longer than those from later lots, thus suggesting reduced fitness as the season advanced. Lot fecundity means ranged from 133 to 312 eggs (maximum 1,036) and 357 to 736 (maximum 1,864) eggs per female for D. barberi and D. virgifera, respectively. Corresponding with greater longevity, increased fecundity was also observed with early-emerging females of both species. Beetles emerging during the first part of the growing season appeared to be generally healthier and more reproductively fit than their latter-emerging counterparts. These findings may warrant further evaluations to determine possible effects on late-season management efforts in adult corn rootworm suppression programs. Methodologies associated with insect maintenance and assessment of reproductive biology proved suitable for both species. Additionally, these findings may offer valuable insight needed to refine procedures for laboratory rearing and egg production from D. barberi.
[Show abstract][Hide abstract] ABSTRACT: Optimization of soil-applied granular insecticides for control of northern and western corn rootworms, Diabrotica barberi Smith &Lawrence and D. virgifera virgifera LeConte, respectively, was investigated in S states in the north central United States. Differences in success ratios (Yes:No, whether root ratings were maintained below the economic injury level) of corn rootworm insecticide rates were analyzed at state and regional levels. The following insecticide rate comparisons were carried out: 0.5 versus 1X rate and 0.75 versus 1X for chlorpyrifos, fonofos, phorate, tefluthrin, terbufos; and 0.6 versus 1X and 0.8 versus 1X for chlorethoxyfos. Regional data also were analyzed using 3.0 and 3.5 (based on 1 to 6 root rating scale) economic injury levels under low, medium, and high rootworm feeding damage. Individual state data were analyzed under combined feeding pressures (low to high) at 'both 3.0 and 3.5 economic injury levels. Under high rootworm pressure and using an economic injury level of 3.0, there were no significant success ratio (lowest versus 1X rate) differences at the regional level, regardless of insecticide. Findings within individual states may be more important than regional analyses when interpreting optimum insecticide rate performances. Significant within state differences between success ratios of low and 1X rates (chlorethoxyfos in South Dakota, chlorpyrifos in Minnesota, fonofos in Iowa, phorate in Iowa and Wisconsin, and terbufos in Iowa), although infrequent, were observed using the more conservative 3.0 economic injury level. No failures were seen using tefluthrin (0.5 versus 1X that was evaluated in only half of the participating states). With the exception of the 0.5 versus 1X fonofos rate comparison in Iowa, all incidences of significant failure were eliminated at the 3.5 economic injury level (lowest versus 1X comparisons). Thus, less-than-labeled rates of these insecticides applied in an IS-cm band can be used to manage rootworm larvae effectively with as much consistency as full (1X) rates.
Journal of Economic Entomology 09/1997; 90(5):1332-1340. · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abundance of ants on mixed-grass rangelands was not significantly reduced by aerial applications of Dimilin 2 F, Dimilin 25 W, and Sevin 4-0il. Ant diversity, measured by a probability of interspecific encounter index, temporarily declined in plots treated with Dimilin 25 W from 13 to 19 d after treatment. However, diversity immediately recovered the following week and no further declines were observed even at 349-356 d after treatment. Twenty species of ants were encountered at the experimental site. Lasius neoniger Emery; little black ant, Monomorium minimum (Buckley);thief ant, Solenopsis molesta (Say);odorous house ant, Tapinoma sessile (Say);and Formica neogagates Emery were the 5 most abundant species at 25.8, 20.1, 9.9, 7.6, and 7.5% of the total number of ants encountered, respectively. Spatial distribution of ant species on rangeland appeared to be soil related. Factor analysis of soil parameters (weighted for relative ant abundances) indicated associations between ant species and certain combinations of soil properties.
[Show abstract][Hide abstract] ABSTRACT: Oviposition habits of adult Diabrotica bar-beri Smith & Lawrence were studied in relation to varying sources of vegetative cover during 1986 and 1987 at three locations in east central South Dakota. Treatments included the following: Corn, Zea mays L.; soybeans, Glycine max L.; simulated volunteer oats, Avena sativa L.; a mixture of green and yellow foxtails, Setaria viridis (L.) Beauvois and S.lutescens (Weigel) Hubb.; Common lambsquarters, Chenopodium album L.; redroot pigweed, Amaranthus retroflexus L.; and Pennsylvania smartweed, Polygonum pennsylvanicum L. Sticky trap data indicated the presence of high beetle populations in plot areas during both years. Totals of 3,447, 8,758, and 14,178 D. barberi were captured at Aurora, Rutland, and Wentworth, respectively. Typically, greater numbers of adults were captured in the Corn plots; however, high numbers were also present within all other treatments. Soil sampling conducted before D. barberi oviposition produced overall means of 1.81, 0.23, and 0.06 eggs per 0.47-liter sample at Rutland, Aurora, and Wentworth, respectively, and indicated that negligible numbers of diapausal eggs were present. Egg recovery after oviposition was significantly (P < 0.01) higher in Corn plots than in nonCorn plots, thus indicating that cornfields provide the preferred site for D. bar-beri oviposition.
Journal of Economic Entomology 01/1992; 85(1):246-249. · 1.60 Impact Factor