Effect of Prevailing Wind Direction
on the Spatial Distribution of
Daily Capture of Boll Weevils
Studies were conducted near remote (>9 miles from other cotton fields) dryland cotton production areas near Caldwell and Waller, Texas, to investigate the effect of prevailing wind direction on the spatial distribution of daily capture of boll weevils (BW). In August 1997, sixty-seven pheromone traps were deployed around the perimeter of cotton fields, in concentric rings at a 2- and 4-mile range, and at a 5-, 6-, 7-, 8- and 9-mile range along a northeast line from the approximate center of the dryland cotton production area. Traps were assigned to eight sectors that were centered on north and at 45-degree intervals. The non-uniform distribution of mean capture of BW by sector was significant using analysis of variance (df = 7, F = 19.13, P < 0.0001). Logistic regression established a significant positive relationship between the daily relative frequency of wind heading and the proportion of daily mean capture by sector (chi square = 26.19, P < 0.05).
Trapping continued at Caldwell from mid-Feb. through Sep., 1998. However, cotton production decreased from 140 acres in 1997 to a single 2-acre cotton field at the center of the trap network in 1998. The trap network was designed with eight sector radials as in August 1997, except that the traps were placed along radials at 1-mile intervals to a range of 5 miles and along four additional radials at 1-mile intervals to a range of 9 miles. Seasonal patterns of trap capture of marked and unmarked boll weevils were examined to determine flight of boll weevils from overwintering habitats into fruiting cotton fields in the spring, and from senescent cotton fields back to overwintering habitats in the fall.
During the spring, boll weevils were captured in pheromone traps; hand-marked with a unique color of paint; and released from eight directional sectors at a range of 2.5 miles from the 2-acre cotton plot. Thirty marked BW were re-captured (0.8%) from seven releases (total of 3,907 BW) at about the date of first third-grown squares in a 2-acre cotton plot at Caldwell. Boll weevils were re-captured at a maximum distance of 5.4 miles from a release site and maximum duration of 11 days after release.
During the fall, boll weevils were captured in pheromone traps; sprayed with a unique color of fluorescent paint; and released near the site of the 2-acre cotton plot on six dates from late-July to mid-September, 1998. Seven-hundred seventy-seven marked BW were recaptured (~3%) from a total release of approximately 25,000 BW. Marked BW were re-captured at a maximum distance of 7 miles and maximum duration of 22 days after release.
A radial network of 50 traps was checked twice weekly at Waller, Texas, from mid-February through June, 1998. No mark-releases were attempted at Waller, but the spatial and temporal distributions of BW will be analyzed. Statistical analysis of the 1998 field data is in progress.
This page was constructed by Gail Kampmeier at gkamp[at]uiuc.edu
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