IMPLICATIONS OF LARVAL MORTALITY AT LOW TEMPERATURES AND HIGH SOIL MOISTURES FOR ESTABLISHMENT OF PINK BOLLWORM (LEPIDOPTERA: GELECHIIDAE) IN SOUTHEASTERN UNITED STATES COTTON.

Authors: VENETTE, ROBERT - USDA-APHIS; Naranjo, Steven; HUTCHISON, WILLIAM - UNIV. OF MINNESOTA

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2000
Publication Date: 12/30/2000
Citation: Venette, R.C., Naranjo, S.E., Hutchison, W.D. 2000. Implications of larval mortality at low temperatures and high soil moistures for establishment of pink bollworm (lepidoptera: gelechiidae) in southeastern united states cotton.. Environmental Entomology 29(5): 1018-1026.

Interpretive Summary: The pink bollworm is a significant pest of cotton in the southwestern US, but has not yet become established in the southeastern United States. Failure to establish may be due to federal regulatory action, climate, or other ecological factors. The objectives of this study were to determine how low temperatures and high soil moisture common to the southeastern US might affect mortality pink bollworm larvae. At constant temperatures in the laboratory, nondiapausing larvae from a colony died more quickly as temperatures were lowered from 22 to 10 to 5C. Under similar experimental conditions, larvae reared under diapause inducing conditions, but showing no developmental evidence of diapause, also died more quickly at lower temperatures. For diapausing, larvae collected from the field, mortality was greater at 5C than at 20, 15, or 10C, but larvae could withstand 5C for >60 days. As soil moisture at 10C became saturated, most larvae died within nthe first 10 d of the experiment. These studies suggest that late-instar pink bollworm larvae are moderately resilient to the effects of low temperature and moisture. Further analysis suggests that winter temperatures in the southeastern US are not sufficiently cold to preclude establishment of pink bollworm.

Technical Abstract: The pink bollworm, Pectinophora gossypiella, remains a significant pest of cotton in the southwestern US, but has not yet become established in the southeastern US. The objectives of this study were to determine how low temperatures and high soil moisture common to the southeastern US might affect mortality of diapausing and nondiapausing larvae of P. gossypiella. At constant temperatures, moisture (0%), and darkness in the laboratory, nondiapausing prepupal larvae from a colony died more quickly as temperatures were lowered from 22 to 10 to 5C. At 5C, 90% of the population was dead after 12 days. Under similar experimental conditions, prepupal larvae reared under diapause inducing conditions, but showing no developmental evidence of diapause, also died more quickly at lower temperatures. In this case, 26 days at 5C were required to achieve 90% mortality. For diapausing, prepupal larvae collected from the field, mortality was greater at 5C than at 20, 15, or 10C, but larvae could withstand 5C for 60 d before 90% of the population died. In response to moisture, as soils at 10C became saturated, most larvae (60%) died within the first 10 d of the experiment. These studies suggest that late-instar larvae of P. gossypiella are moderately resilient to the effects of low temperature and moisture. Diapausing individuals are more resilient to low temperatures than nondiapausing individuals. Winter temperatures in the southeastern US are not sufficiently cold to preclude establishment.