Aerial concentrations of gossyplure, the sex pheromone of the pink bollworm (Lepidoptera: Gelechiidae), within and above cotton fields treated with long-lasting dispensers

Cotton plants, Gossypium spp. were treated with long-lasting dispensers containing gossyplure, the sex pheromone of the pink bollworm, Pectinophora gossypiella (Saunders). Samples of air from 0.15 m above ground level and from above the tops of plants were pulled through adsorbent cartridges during day and night periods (0600-1800 and 1800-0600 hours [PST], respectively) and analyzed by gas chromatography for gossyplure content. The gossyplure was applied in Shin-Etsu rope or bag dispensers to 5-ha areas at rates of 86.8 or 71.6 g AI/ha, respectively, at the pin-square (first-flower bud) stage of plant development. Air samples were taken during 3-d periods beginning 20, 40, 63, and 84 d after application. Ten Delta traps, each baited with 1 mg of gossyplure, were used to capture males in each treated area and an untreated control field. Eight samples of 200 bolls per area were collected weekly from treated and control areas during August and September and incubated for 2 wk before counts of pink bollworm were made. Temperatures and wind speed were recorded at 0.3 and 1.8 m above ground level in the cotton field. Temperatures and wind speeds were similar at 0.3 and 1.8 m above ground level when the cotton plants were small, but as the plants grew, temperatures were 4 degrees C lower and wind speeds were reduced to <0.5 m/s at 0.3 m. Emission of gossyplure from rope dispensers was greatest following application and then declined, whereas the emission from bag dispensers increased slightly throughout the test period. Trap catch of males in both treated areas was reduced 99% compared with the control area during 60 d following application. No pink bollworm were found in 1,600 bolls collected from each treated area compared with 13 pink bollworm collected from the control area. Aerial concentrations of gossyplure followed similar patterns in rope and bag fields during canopy formation. Daytime and nighttime aerial concentrations of gossyplure at 0.15 m increased significantly during the test, whereas concentrations at the tops of the plants changed little. These results show that the nighttime aerial concentrations in the mating arena of moths at the tops of the plants do not reflect the increasing concentrations at 0.15 m as obtained with the dispensers applied at pin-square.