Pink Bollworm Biology: Effects of High Soil Temperature on Larvae under Laboratory and Field Conditions

Abstract

In laboratory tests (simulated field conditions), larvae of pink bollworm, Pectinophora gossypiella (Saunders), suffered high mortality when soil temperatures were 47°–51°C. However, at these conditions, irrigated-cracked soil provided a protective habitat; cultivated soil reduced larval mobility and caused maximum exposure to the high temperatures. If possible, larvae that fell to the soil moved quickly to avoid high soil temperatures; but then as the temperature decreased, they often moved to alternate pupation sites. On occasion, reproduction of moths from larvae that survived high temperatures was reduced, but results were variable. In field tests of cotton, Gossypium hirsutum L., results were similar. Larval mortality was highest early in the season before plants were large enough to shade the soil. A high percentage of the larvae released on the slopes of the plant beds reached the top of the plant bed and survived. Broad, flat plant bed tops favored survival of pink bollworm larvae more than peaked plant bed tops. Peaking the plant bed to reduce top surface area and increase the angle of the slope and cultivating the bed after the larvae cut out and fell to the soil surface resulted in 70% reduction in emergence of adult moths.