The impact of actual and surrogate variegated cutworm stubble phytophagy on the growth and yield of alfalfa

The response of alfalfa regrowth to actual and simulated stubble damage by the variegated cutworm (VCW), Peridroma saucia (Hubner), was investigated. A laboratory study found that most larvae exhibited 7 larval stages. Development by these larvae took 32.8 days at 24(DEGREES)C, during which 442.2 mg of alfalfa foliage was consumed;The effect of the duration of a complete suppression of regrowth on alfalfa productivity was studied using a surrogate defoliation technique. Complete regrowth suppression for 1 and 3 days did not significantly affect alfalfa regrowth. Delays of 7 and 11 days retarded plant development and suppressed the crop growth rate (CGR) of subsequent regrowth. Most of the reduction in CGR was caused by a decline in the growth rate of support (stem) structures. Leaf-weight and leaf-area growth rates were not significantly affected. The differential response of component growth rates resulted in an increase in the leaf area ratio, leaf weight ratio, and specific leaf area of regrowth;A second study found that stubble damage by various densities of VCW larvae produced the same general effects on alfalfa growth and partitioning that simulated defoliation produced. The effects, however, were significant in all years only for densities of 6 and greater larvae/0.1 m(\u272). These densities were large enough to completely suppress regrowth in most years for 10 to 15 days;The results of both studies indicated that plants minimized the adverse effects of stubble injury by maintaining growth rates of leaf weight and area at the expense of support-structure growth. A hypothesis based on the depletion of stored carbohydrate reserves was proposed to explain the changes observed in alfalfa regrowth;A replacement-feed cost analysis was conducted for both studies. Depending on commodity price and control costs, stubble damage was economic for a harvest system based on cutting at first bloom when regrowth was suppressed completely for 4.4 to 7.5 days or when densities of newly-molted, last-stage larvae reached 2.8 to 4.8 larvae/0.1 m(\u272). Action levels were reduced by approximately one-half if cutting occurred based on calendar-date. A management program for VCW in alfalfa was developed using these results, and guidelines for the management of other stubble defoliators also were proposed

Insect-Attracting and Antimicrobial Properties of Antifreeze for Monitoring Insect Pests and Natural Enemies in Stored Corn

Insect infestations in stored grain cause extensive damage worldwide. Storage insect pests, including the Indianmeal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae); Sitophilus spp. (Coleoptera: Curculionidae); and their natural enemies [e.g., Cephalonomia tarsalis (Ashmead) (Hymenoptera: Bethylidae), and Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae)] inhabit a temporary, but stable ecosystem with constant environmental conditions. The objective of the present experiment was to assess the efficacy of using ethylene glycol antifreeze in combination with nutrient solutions to monitor storage insect pest and natural enemy populations in three bins of corn, Zea mays L. The treatments were deionized water, a diluted (1:5 antifreeze:water) antifreeze solution, 10% honey, 10% honey in the diluted antifreeze solution, 10% beer in the diluted antifreeze solution, 10% sucrose in the diluted antifreeze solution, and a commercial pheromone trap suspended in a 3.8-liter container filled with 300-ml of diluted antifreeze solution. The seven treatments captured storage insect pests and their natural enemies in the bins at 33-36°C and 51-55% RH. The pheromone trap in the container with the diluted antifreeze captured significantly more P. interpunctella than the other treatments, but a lower percentage (7.6%) of these captures were females compared with the rest of the treatments (\u3e40% females). All trapping solutions also captured Sitophilus spp. and other beetle species, but the captures of the coleopteran pests were not significantly different among the seven treatments (P \u3e 0.05). Two parasitoid wasps also were captured in the study. The number of A. calandrae was different among the seven treatments (P \u3c 0.05), whereas the number of C. tarsalis was not different among the treatments (P \u3e 0.05). Most A. calandrae adults were captured by the 10% honey in the diluted antifreeze, whereas the fewest were captured in the deionized water. Microbial growth was observed in the 10% honey solution, but no microbial growth occurred in the rest of the treatments, including 10% honey in the diluted antifreeze solution. The results of insect captures and microbial growth demonstrated that antifreeze could be used as a part of storage insect monitoring and/or control programs

Spatial Patterns of Aflatoxin Levels in Relation to Ear-Feeding Insect Damage in Pre-Harvest Corn

Key impediments to increased corn yield and quality in the southeastern US coastal plain region are damage by ear-feeding insects and aflatoxin contamination caused by infection of Aspergillus flavus. Key ear-feeding insects are corn earworm, Helicoverpa zea, fall armyworm, Spodoptera frugiperda, maize weevil, Sitophilus zeamais, and brown stink bug, Euschistus servus. In 2006 and 2007, aflatoxin contamination and insect damage were sampled before harvest in three 0.4-hectare corn fields using a grid sampling method. The feeding damage by each of ear/kernel-feeding insects (i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs), and maize weevil population were assessed at each grid point with five ears. The spatial distribution pattern of aflatoxin contamination was also assessed using the corn samples collected at each sampling point. Aflatoxin level was correlated to the number of maize weevils and stink bug-discolored kernels, but not closely correlated to either husk coverage or corn earworm damage. Contour maps of the maize weevil populations, stink bug-damaged kernels, and aflatoxin levels exhibited an aggregated distribution pattern with a strong edge effect on all three parameters. The separation of silk- and cob-feeding insects from kernel-feeding insects, as well as chewing (i.e., the corn earworm and maize weevil) and piercing-sucking insects (i.e., the stink bugs) and their damage in relation to aflatoxin accumulation is economically important. Both theoretic and applied ramifications of this study were discussed by proposing a hypothesis on the underlying mechanisms of the aggregated distribution patterns and strong edge effect of insect damage and aflatoxin contamination, and by discussing possible management tactics for aflatoxin reduction by proper management of kernel-feeding insects. Future directions on basic and applied research related to aflatoxin contamination are also discussed

Parasitoids (Hymenoptera: Chalcidoidea) of the Cabbage Seedpod Weevil (Coleoptera: Curculionidae) in Georgia, USA

Volume: 15Start Page: 187End Page: 20

Insect-Attracting and Antimicrobial Properties of Antifreeze for Monitoring Insect Pests and Natural Enemies in Stored Corn

Insect infestations in stored grain cause extensive damage worldwide. Storage insect pests, including the Indianmeal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae); Sitophilus spp. (Coleoptera: Curculionidae); and their natural enemies [e.g., Cephalonomia tarsalis (Ashmead) (Hymenoptera: Bethylidae), and Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae)] inhabit a temporary, but stable ecosystem with constant environmental conditions. The objective of the present experiment was to assess the efficacy of using ethylene glycol antifreeze in combination with nutrient solutions to monitor storage insect pest and natural enemy populations in three bins of corn, Zea mays L. The treatments were deionized water, a diluted (1:5 antifreeze:water) antifreeze solution, 10% honey, 10% honey in the diluted antifreeze solution, 10% beer in the diluted antifreeze solution, 10% sucrose in the diluted antifreeze solution, and a commercial pheromone trap suspended in a 3.8-liter container filled with 300-ml of diluted antifreeze solution. The seven treatments captured storage insect pests and their natural enemies in the bins at 33-36°C and 51-55% RH. The pheromone trap in the container with the diluted antifreeze captured significantly more P. interpunctella than the other treatments, but a lower percentage (7.6%) of these captures were females compared with the rest of the treatments (\u3e40% females). All trapping solutions also captured Sitophilus spp. and other beetle species, but the captures of the coleopteran pests were not significantly different among the seven treatments (P \u3e 0.05). Two parasitoid wasps also were captured in the study. The number of A. calandrae was different among the seven treatments (P \u3c 0.05), whereas the number of C. tarsalis was not different among the treatments (P \u3e 0.05). Most A. calandrae adults were captured by the 10% honey in the diluted antifreeze, whereas the fewest were captured in the deionized water. Microbial growth was observed in the 10% honey solution, but no microbial growth occurred in the rest of the treatments, including 10% honey in the diluted antifreeze solution. The results of insect captures and microbial growth demonstrated that antifreeze could be used as a part of storage insect monitoring and/or control programs

Quantitative Trait Locus Analysis of Hessian Fly Resistance in Soft Red Winter Wheat

The Hessian fly (HF) is an invasive insect that has caused millions of dollars in yield losses to southeastern US wheat farms. Genetic resistance is the most sustainable solution to control HF. However, emerging biotypes are quickly overcoming resistance genes in the southeast; therefore, identifying novel sources of resistance is critical. The resistant line “UGA 111729” and susceptible variety “AGS 2038” were crossbred to generate a population of 225 recombinant inbred lines. This population was phenotyped in the growth chamber (GC) during 2019 and 2021 and in field (F) trials in Georgia during the 2021–2022 growing seasons. Visual scoring was utilized in GC studies. The percentage of infested tillers and number of pupae/larvae per tiller, and infested tiller per sample were measured in studies from 2021 to 2022. Averaging across all traits, a major QTL on chromosome 3D explained 42.27% (GC) and 10.43% (F) phenotypic variance within 9.86 centimorgans (cM). SNP marker IWB65911 was associated with the quantitative trait locus (QTL) peak with logarithm of odds (LOD) values of 14.98 (F) and 62.22 (GC). IWB65911 colocalized with resistance gene H32. KASP marker validation verified that UGA 111729 and KS89WGRC06 express H32. IWB65911 may be used for marker-assisted selection