Recipient Organization
VIRGINIA POLYTECHNIC INSTITUTE
(N/A)
BLACKSBURG,VA 24061
Performing Department
Tidewater Agri Research & Extension Ctr
Non Technical Summary
1. Most field corn grown in Virginia is Bt corn, which expresses insect-active toxins from the bacterium, Bacillus thuringiensis (Bt) in tissues of the plant. Bt corn does not always provide 100% control of corn earworm, and thus supplemental insecticide sprays are often needed to ensure quality ears, especially during high moth activity. Our survey is a way to track field-evolved resistance and associated reduction in control efficacy from Bt corn on a statewide scale. Corn is considered a nursery crop for corn earworm, allowing the pest to complete a lifecycle and then move on to other crops such as soybean, cotton, and peanut in August. Over 30 years of data show that there is a linear correlation between the infestation level in corn and the amount of acreage that gets treated with insecticides for this pest.2. Producers are looking for the most affordable ways to manage insect pests. One way to reduce costs associated with pest management is to identify where insecticide resistant pests are present and to identify what products offer best control. Corn earworm, Helicoverpa zea (Boddie), is a major pest of corn, cotton, soybean, sorghum, and other agricultural products in Virginia. Control of corn earworm in Virginia and across the Southeast has relied heavily upon pyrethroid insecticides. Pyrethroids have provided consistent control of corn earworm in Virginia until very recently, with more and more Virginia growers reporting pyrethroid spray failures. One way pyrethroid resistance is tracked using the adult vial bioassay - these tests have been run for a number of years in southeastern Virginia. Results are used to track insecticide resistance levels over time, inform growers of local pest situations, detect regional patterns in insect resistance, and help control pest management costs--including minimizing applications of ineffective and/or unnecessary insecticides.3. Currently, all Bt maize seed is sold with neonicotinoid seed treatments (NSTs), namely clothianidin and thiamethoxam, labeled for rootworm control. Despite widespread use, the relative contribution of NSTs to insect control (including resistance management) in Bt maize is completely undescribed. Our first objective is to fill this data gap by investigating whether NSTs affect resistance management by changing the ratios of insects from Bt and refuge plants. We will also examine the economic need for NSTs to prevent root injury and yield loss from soil insects in Virginia. While abundant data on environmental impacts exist for Bt products, the costs/benefits of persistent, nearly ubiquitous NST residues on soil health have not been measured. Using novel methods developed by our group, we will quantify rootworm emergence from refuges with and without NSTs, then characterize the value of the control NSTs provide by complementing insect-resistant Bt maize hybrids. We will collect data on insecticide residues in soil and water in these experiments. The overall goal of this research is to provide foundational data to guide the use of insecticidal seed treatments in a way that does not compromise resistance management, while providing growers protection from root-feeding pests where appropriate.
Animal Health Component
95%
Research Effort Categories
Basic
5%
Applied
95%
Developmental
0%
Goals / Objectives Investigate the relationship between pest management technologies and the agricultural environment. 1a. Assess the need, efficacy and pest management window of seed treatment insecticides, primarily neonicotinoids, to control secondary below-ground insect pests.
1b. Evaluate possible effects of insecticidal seed coatings on non-target beneficial insects.
Develop and assess IPM and IRM systems for the arthropod complex in corn.
3a. Characterize and monitor for resistance of lepidopteran pests to Bt corn and conventional insecticides, and assess possible IRM and mitigation strategies.
3b. Characterize geographic extent and nature of resistance of Diabrotica spp. to Cry toxins, pyrethroids, and other insecticides, and develop appropriate IPM and IRM strategies for problem areas.
3c. Work toward improving an artificial diet for WCR rearing and more sensitive bioassays of toxins.
3d. Develop strategies to manage the ear-feeding pest complex and model implications for IRM and IPM.
3e. Develop Helicoverpa armigera early detection and mitigation network.
3f. Develop region-specific bioeconomic models to assess refuge and IPM strategies for managing lepidopteran and coleopteran pest resistance to Bt corn expressing stacked and pyramided toxins.
3g. Assess the extent to which limited farmer access to Bt corn varieties targeting only coleopteran or only lepidopteran pests affects the risk of resistance when the economic importance of each pest varies regionally.
Employ diverse delivery methods to disseminate information related to sustainable management of corn arthropod pests.
4a. Establish an NC-205 video library website with permanent high quality versions of IPM videos for open online access and download to computer and portable electronic devices.
4b. Produce and deploy a comprehensive IPM system for cost-effective prevention, early detection, rapid diagnosis, and mitigation of new and emerging corn pests that links all stakeholders who have common interests in pest detection and management.
4c. Develop an array of IPM and IRM distance education workshops.
Project Methods
1) Corn Earworm Field Corn Survey:Annual surveys will be used to estimate Helicoverpa zea (corn earworm) infestation levels in field corn in mid- to late July. Virginia Cooperative Extension Agriculture and Natural Resource (ANR) Agents and/or Virginia Tech faculty and staff record the number of corn earworm larvae found in 50 ears of corn in five cornfields per participating county. All three regions of Virginia (e.g., coastal plain, piedmont, mountains) will be represented. When fields are known to contain Bt, non-Bt, or "refuge in a bag" (RIB) corn, this will be noted. Otherwise, samples will be considered random and assumed to be representative of the actual Bt/non-Bt composition in each county. Age of corn earworms, or if they had already exited the ears, will also be recorded.2) Corn earworm pyrethroid resistance monitoring:Entomology personnel will operate pheromone-baited traps for corn earworm moths (Gempler's, Janesville, WI, USA) at two Virginia Agricultural Research and Extension Centers (ARECs) (Tidewater AREC in Suffolk, and Eastern Shore AREC inPainter) and the Virginia Tech Agricultural Experiment Station, Blacksburg, (May-September). Three to five traps per location will be positioned in open areas bordering soybean and/or corn fields. Corn earworm moths caught from each location that appear visually healthy (i.e., wings not damaged; majority of wing scales intact) will be assessed for pyrethroid resistance using the adult vial test. The vial test exposes the moths to a residual concentration of pesticide (5 micrograms cypermethrin - a pyrethroid standard) for 24 hours. Vials will be prepared at the Tidewater Agricultural Research and Extension Center following the protocol developed by Fred Musser at Mississippi State University and using technical grade pyrethroid insecticide, with acetone-only vials as the control. Moths will be assessed for survival 24 hours after being placed into vials by categorizing them as dead, down (unable to fly), or alive.3) Neonicotinoid seed treatments in Bt maize: a) We will conduct experiments at two field locations in Virginia for two years. Fields will be located at research stations or on the farms of cooperating growers where natural infestations of western corn rootworm (WCR) and other soil pests are consistent. We will assess the presence and abundance of non-western corn rootworm (WCR) soil pests, by taking soil samples from four locations in each plot prior to planting. We will plant to test seeds treated with and without the NST clothianidin (trade name: Poncho®) at the 'rootworm' rate of 1.25 mg/a.i. per kernel. Bt and refuge seeds will be from a "refuge in a bag" mix of Genuity SmartStax® (for example, DKC 61-16) (DeKalb; Monsanto, St. Louis, MO) with Bt corn hybrids that express Cry3Bb1 and Cry34/35Ab1 toxins for WCR control. We will plant into areas of continuous corn and surround field plots with soybean, woody borders, or field cages. We will sample plots beginning at appearance of the first adult WCR in each location and record adult rootworm emergence. We will measure root damage in each plot twice, ca. July 20 and Aug 1. At each interval, four consecutive plants/row will be removed and root injury assessed. Plants will be harvested, and yield and grain moisture measured, between mid and late September. Secondary soil pests (wireworms, white grubs) and their damage will be assessed by estimating plant populations (i.e., stand counts) ca. 1 week following emergence by counting the number of plants in a row from converting this value to plants per hectare.b) We will measure neonicotinoid residue levels in soils and surface water from plots in 3a. Soil samples will be collected from 4 cm below the soil surface to avoid sampling topsoil. Using 10 cm diameter x 15 cm soil cores, we will collect samples at five random locations in the field. These samples will be combined in a 3.78 liter bucket, mixed, and a subsample of the pooled soil transported to the lab in paper bags stored in coolers to minimize the possibility of photolysis. Samples will be stored at -20°C until analysis. Water samples will be collected from ditches and waterways adjacent to fields, using 1-L amber glass bottles and transported to the laboratory on ice. Water samples will be processed within 96 h after collection. All samples will be analyzed using a modified version of the QuECHeRs protocol.