To seek alternatives for the control of the pink bollworm (PBW), Pectinophora fella (Saunders), in the southwestern deserts, internal boll temperatures (IBT) of cotton, Gossypium hirsutum L., were studied. Thermocouples imbedded in the cotton bolls showed that, by exposing bolls to the sun by defoliation, IBT were increased by 2 to 6 C, as compared to bolls shaded under the canopy between 0800 and 1800 h in the six-day period from August 28 to September 3, 1986. Coating the exposed bolls with a clear acrylic film increased IBT further by 1 to 5 C. The IBT were greater than 40 C for eight hours between 1100 and 1800 h, inclusive. Nevertheless, PBW larvae survived the heat created in the cotton bolls.

Coating exposed bolls also significantly increased IBT as compared to shaded bolls between 0900 and 1800 h in the six-day period from Sept. 26 to Oct. 1, 1986. But, IBT were well below 40 C.