Boll weevil (Coleoptera: Curculionidae) response to and volatilization rates of grandlure when combined with varying doses of eugenol in the extended-life pheromone lure.

Boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), trapping and pheromone quantitative analysis of extended-life pheromone lures manufactured with 0, 10, 20, and 30 mg of eugenol was conducted in the Rio Grande Valley of Texas under spring and summer conditions. Boll weevils responded positively to eugenol on one of 12 trapping weeks when densities were high, but when densities were low (<2 weevils trap(-1) wk(-1)), there were no significant differences in captures for any dosage of eugenol offered in a standard boll weevil trap. Weekly grandlure volatilization did not differ by eugenol dose but was significantly different when evaluated over three different trapping periods and by week within trapping period due to differences in ambient temperature. The amount of grandlure that remained after 4 wk in moderate temperatures of spring was 13.1 +/- 0.19 mg (55.7% of original 25 mg of content) compared with 5.5 +/- 0.15 mg remaining (22.8% of original 25 mg content) after for 4 wk in summer heat. Weekly volatilization of grandlure for the summer trapping period was 9.8 +/- 0.32 mg for the first week, declining steadily to 1.0 +/- 0.09 mg by the fourth week of age. The data indicate that at high summer temperatures >30 degrees C, accumulative grandlure loss per week may be too high, leaving too little residual grandlure to effectively attract boll weevils at the end of 3 wk of trapping. Eugenol plays no role in reserving or encouraging the release of grandlure, or in increasing boll weevil captures when boll weevil densities are low.