Extension - Management of Soil and Stalk Boring Insects on Field Corn
PI(s): Youngman, Roger R
Investigators: Laub, Curt
Abstract: Field corn harvested for grain and silage serves as a high quality source of feed for the beef, dairy cattle, and poultry industries in Virginia. Cash receipts for corn grain production in 2005 totaled more than $89 million, in addition to $68 million in gross value for corn silage production (2006 Va. Agric. Statistics Bull.). The primary insect pests on corn in Virginia are the western corn rootworm and European corn borer. In addition to these, several secondary pests, such as annual white grubs, wireworms, and seedcorn maggot continue to be a main focus area for my extension and applied research efforts.
Description: Program Outcomes: The economic threshold is the backbone of most IPM programs on field crops. An applied research emphasis for my program since 2004 has been to determine an economic injury level for European corn borer stalk tunneling on corn harvested for silage. The economic injury level is the basis for the economic threshold. I expect our findings to be well received by the farming community, given that applied research of this nature has not previously been done in Virginia. Research is already underway to repeat this work on corn harvested for grain. Another program emphasis since 2003 concerns the relatively new seed-applied insecticides. Numerous on-farm trials on pre-plant soil sampling methods and novel insecticidal seed treatments have been conducted in eastern Virginia. These materials show promise in managing secondary pest insects that attack the newly planted corn seed. Feeding by secondary pests leads to uneven plant stands, reduced seedling vigor, and lower yields and forage quality. Specific findings indicate that two insecticides consistently provide superior control of secondary pests, with the possible exception of cornfields heavily infested by annual white grubs. In cornfields where western corn rootworm is not a problem (which includes most of eastern Virginia), using insecticidal seed treatments instead of granular insecticides at planting may ultimately save growers $15-$20 per acre in reduced insecticide costs. These findings have enabled me to annually update Extension Agents, growers, and agribusiness professionals on these pest management tools. Future studies are aimed at heavily infested white grub fields to further challenge the performance of these materials. A new direction for my lab involves using fall soil sampling estimates of overwintering annual white grubs and wireworms to predict their pest potential in fields planted in corn the following spring. Fall soil sampling methods and economic thresholds for predicting fields at risk to secondary pests are necessary to provide corn growers sufficient time to include a seed-applied insecticide treatment with their order. Insecticidal seed treatments are applied directly to the corn seed by the manufacturer at the time the seed order is placed. Consequently, seed orders need to be placed well in advance of the next growing season. Our 2005 fall soil sampling indicated that 80% of the sampled fields had above-threshold counts of annual white grubs. Cooperating growers and extension agents were interested in these findings to the point of using the information for their own purposes. Fall of 2007 is the earliest that a research-based, fall soil sampling threshold will be available.
Commodities: Corn, Forages
Resources: Agricultural Experiment Station Facilities, Computer Workstations, Department Shop, Entomology Laboratory - Southern Piedmont AREC, Insect Identification Laboratory, Insecticide Storage Building, Price Hall, State-Owned Vehicles
Disciplines: Environmental Quality, Integrated Pest Management, Pesticides
Audiences: Agribusiness, Commodity Groups, Extension Agents, Government Agencies, Graduate Students, Producers, Prospective Students
