Date of Award:

5-1-1979

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Donald W. Davis

Committee

Donald W. Davis

Committee

Lamar J. Anderson

Committee

B. Austin Haws

Abstract

The purpose of this study was to assess the impact of high temperature and low and moderate relative humidity on the survival of 1 to 3-day old nondiapausing pupae of Bathyplectes curculionis (Thomson). Temperature and time, independently and dependently, were significant factors to mortality, but relative humidity was not. No mortality was shown at 25°C and 60 to 70% relative humidity at exposures of 24 h or less. As temperatures were raised above 25°C the initially low mortality increased but in a nonlinear pattern, reaching 100% with high correlation for short exposures at 43°C or higher. At each temperature near 30°C or above, mortality increased linearly as exposure times were lengthened. At 13 to 26% relative humidity the LT50 (lethal time for 50% mortality) values were: 30°C = 25.17± 2.96 h (standard error), 35°C = 20.87±4,10 h, 38°C = 16.58±1,79 h, 40°c = 9.77±1.22 h, 43°c = 1.08+0.62 h, 45°C = 25.20±8,40 min, 48°C = 18.60+4.20 min. At temperatures between 30 and 38°C with 720 to 1080-min exposures, mortality averaged 10% greater at 20% relative humidity than at 70% relative humidity. At 43°C or higher, mortality at the two humidity levels was not measureably different. Field observations indicated that dry unshaded soil was 50°C or about 20°C warmer than uncut alfalfa field soil. Accordingly, the findings of this study indicate that long exposures of temperatures of 43°C and below or short exposures above 43°C will illicit high mortality in nondiapausing B. curculionis. The exact mortality level will depend on exposure time.

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