FINAL REPORT

1998-99 Fire Ant Research and Extension Program

June 30, 1999

Title: Studies on Distribution and Mound Size of the Red Imported Fire Ant Under Varying

Cropping Practices (1781)

Funding Level: $9,400

Participants/Collaborators: Donald G. Manley, Warren J. Busscher, and John C. Hayes

Statement of Problem Prompting Research Initiative: Large fire ant mounds present a major problem to growers. Although the fire ants are beneficial with respect to their predatory capabilities, when farm machinery hits large mounds, considerable damage may result. Although it is known that soil type, cultivation, and vegetative cover influences both mound size and distribution, few specifics are known. The overall objective of this study is to determine some of these specific influences.

Scope of Investigation: Studies are being conducted on the split-landscape agroecology field at the Pee Dee Research and Education Center in Florence. Half of this field is being grown using standard agronomic practices. The other half is being grown using innovative agronomic practices, including reduced tillage and narrow row spacing. Red imported fire ant (RIFA) colonies are being mapped out, over time, showing the number and distribution of mounds under the different cropping practices. Probes are also being used to determine mound size and depth under the varying conditions.

Accomplishments & Results: All fire ant mounds in the split-landscape field (both sides) were flagged in June 1998, shortly after planting of soybeans. Using GIS and GPS technologies, the RIFA colonies were mapped for both sides and compared. At that time, there were nine mounds/acre in the conventional side, and 5.4/acre in the innovative side. The procedure was repeated in the Fall, after soybean harvest. At that time, there were 18 mounds/acre in the conventional side, and 44/acre in the innovative side, an increase of about 2x and 9x, respectively. The procedure was repeated in the Spring of 1999, after corn planting. At that time, the number of mounds/acre was 49 and 37, respectively.

Using probes pushed into mounds on a 4-inch grid, fire ant excavation was measured. Preliminary results showed that mounds are slightly deeper on the innovative side, but that the difference was not significant. More measurements are needed.

Summary Statement: Preliminary results indicate that there is no significant difference in RIFA mound size in the two sides of the split field. However, the innovative practices may be contributing to a greater number of mounds overall. Further study over time is needed.