Name: Dr. Glynn Tillman
Title: Research Entomologist
Research: Sustainable Agricultural Systems and Conservation of Natural Enemies. Specific research includes studying the use of selective insecticides for control of pest species, evaluating trap crops to trap pest species and enhance natural enemies in cotton, and growing winter cover crops to provide refuges of natural enemies and improve soil quality in cotton.
Support Staff: Penny Tapp
Address: Crop Protection and Management Research Unit
USDA-ARS
P.O. Box 748
Tifton, GA 31793-0748
Phone: 229-3872343
FAX: 229-387-2321
E-Mail: PGT@tifton.usda.gov
Education: B.S., Augusta State University, Biology
M.S., Georgia Southern University, Biology
Ph.D., Texas A&M University, Entomology
CRIS Project Title: Sustainable Systems for Integrated Pest Management and Conservation and Enhancement of Natural Enemies
Research Goals: Evaluate the use of selective insecticides for control of pest species, trap crops to trap pest species and enhance natural enemies in cotton, and winter cover crops to provide refuges of natural enemies and improve soil quality in cotton.
Major Accomplishments:
Indoxacarb is a new oxadiazine insecticide that has shown outstanding field insecticidal activity. The toxicity of Steward™, a formulation of indoxacarb, was studied on the tarnished plant bug Lygus lineolaris and the big-eyed bug Geocoris punctipes. Both insect species responded very similarly to Steward in topical, tarsal contact, and plant feeding toxicity studies. The topical LD50 for Steward was c 35 ng of active ingredient per insect for both species. Prolonged tarsal contact with dry Steward residues did not result in mortality for either insect species. However, both species were susceptible to feeding through dried residues of Steward after spraying on young cotton plants. Feeding on water-washed plants resulted in lower mortality than that observed for unwashed plants, and toxicity declined even more dramatically after a detergent rinse, indicating that much of the indoxacarb active ingredient probably resides on the cotton's surface or in the waxy cuticle. These results were corroborated by HPLC-mass spectrometry measurements of indoxacarb residues on the plants. Greater mortality for both species was observed in a higher relative humidity environment. Higher levels of accumulated indoxacarb and its active metabolite were detected in dead G. punctipes than L. lineolaris after feeding on sprayed, unwashed plants. When female G. punctipes ate Steward-treated H. zea eggs, there was significant toxicity. However, only 15% of the females consumed Steward-treated eggs, and in fact a significant diminution of feeding was observed in response to the insecticide for the rest of the females. Cotton field studies have shown that Steward treatments at labeled rates lead to a dramatic decline in L. lineolaris, with negligible declines in beneficial populations. A major route of intoxication of L. lineolaris in Steward-treated cotton fields thus appears to be via oral, and not cuticular, uptake of Steward residues from treated cotton plants. The mechanisms for selectivity/safety for G. punctipes are currently under investigation and may be a combination of differential feeding behavior and diminution of feeding by females exposed to Steward treated eggs.
The ability of a strip crop of sorghum to serve as a trap crop for the corn earworm in cotton was investigated in Mystic, GA in 2000. A strip of sorghum, 8 rows by 400 feet, was planted in the center of a 2.4 acre cotton plot which was located at one end of a cotton field. Corn earworm populations were monitored in the sorghum strip, in cotton adjacent to the sorghum, and in cotton in a control plot located at the other end of the cotton field. The mean number of corn earworm eggs/acre was higher in the grain sorghum than in the cotton. These results demonstrated that the corn earworm was more attracted to sorghum than cotton, and thus grain sorghum was an effective trap crop for the corn earworm in cotton. Total real mortality (rx) of the corn earworm in sorghum was very high, and so the sorghum trapped the pest insect without becoming a source of the insect in cotton. This test will be repeated in 2001.
Using on-farm studies the effects of increasing cover crop diversity on beneficial insect abundance, belowground soil biological activity, soil nutrient and water availability, and economics of conservation tillage cotton will be evaluated on farms near Louisville, GA and Tifton, GA over three years beginning in 2001. The primary on-farm study will compare traditional cover crop practices to two diverse cover crop mixtures designed to extend availability of food sources to beneficial insects and increase biomass inputs to improve soil organic matter content. Cover crops in the mixture were chosen based on early, midseason, and late blooming characteristics and their adaptation to the area. Four 10 acre fields will be used for each treatment specifically for evaluating aboveground. Cover crop treatments include: 1) no cover crop- conventional practice where farmers allow weeds to grow during the winter, (2) cereal rye - standard grass cover crop, (3) legume blend - balansa clover, crimson clover, and hairy vetch mixture chosen to extend flowering (early, mid, and late flowering respectively), and (4) combination of legume blend plus rye - combines benefits of legume nectar production and N fixation with enhanced biomass production of rye. At the Tifton location an additional treatment was added to evaluate mixtures against the standard legume cover crop (5) crimson clover. Cooperators are providing enough land to establish one complete set of treatments within close proximity so that farm location will be used as replicates. Fields were chosen to ensure homogenous soil types for all fields within a location. In addition, during the first 2 years additional cover crops will be evaluated in on-station and on-farm studies to refine effectiveness of the cover crop mixtures as insect habitat and biomass input. Cover crops will be evaluated singly and in 2, 3, and 4 part mixtures. In year three we will compare newly developed mixtures against the original mixtures in on-farm trials at multiple locations in the state.
Poster (Grain Sorghum as a Trap Crop for the Corn Earworm)
