BOLL WEEVIL DENSITY AND DISTRIBUTION IN TENNESSEE COTTON
Ronnie W. Seward, University of Tennessee
West Tennessee cotton producers experienced the highest incidence of over-wintered boll weevil in more than a decade at the start of the 1998 crop. This was based on pheromone-trap capture records and personal communication with extension agents, producers and consultants throughout the area. Approximately 500 traps were utilized in a "trap line network" across nineteen counties and serviced weekly by extension service personnel. The objective was to continue documenting the variation of boll weevil populations across West Tennessee and collect timely data that would benefit cotton producers for immediate and future management decisions. Trap counts were disseminated by e-mail, web page, newsletters, news releases, radio and DTN electronic media. Hundreds of producers and their advisors were able to make better decisions to improve the economic and yield potential of the crop. These unusually high counts contributed to more acres receiving pinhead square applications than had previously been seen.
Four of five years trapping data, 1994-1998, have consistently shown higher populations during the spring in the southern counties (bordering Mississippi) versus the central and northern counties (bordering Kentucky). This year was an exception in that boll weevil numbers in the central counties were similar to those in the southern counties. Northern counties were above average. Several individual traps in ten of nineteen counties captured 400-700 weevils per week. These counties were: Fayette, Hardeman, Tipton, Haywood, Madison, Chester, Carroll, Lauderdale, Crockett and Gibson. Peak emergence of over-wintered boll weevil was observed during the third week of May with an average of 132 weevils per trap. This was 25-30 days earlier than peak emergence in 1997 with a 63% increase in average number of weevils captured.
Trap monitoring was continued from August to November for determining the number of boll weevils that were moving/migrating and preparing to enter their over-wintering habitat. Peak trap capture was observed during the last few days of September and early October. Trap data collected during this period also helped evaluate the results of a fall diapause spray program to start eradication in Zone 1, the southern counties and the area south of the Hatchie River. During August and September, three- to five-fold higher trap captures were recorded outside the eradication zone and these increased to ten-fold higher during October.
This data continue to support the following: (1) variability in boll weevil emergence, (2) the need for timely pinhead-square insecticide applications, (3) the potential increase in late season boll weevil numbers if not controlled, and (4) how an eradication program can quickly reduce the numbers of boll weevils before they can enter their over-wintering habitat.
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