干旱区生态环境知识资源中心

Little is known about high temperature thresholds for the whitefly Bemisia argentifolii Bellows & Perring, which thrives during the hot summers common to the southwestern deserts of the United States. This study addressed 3 questions relating to B. a tifolii thermal responses. (1) What are the maximum, optimum, and minimum leaf temperatures for oviposition rate? (2) Is the optimum temperature for oviposition dependent on temperature effects on insect physiology or on host plant thermal responses? (3) How does B. argentifolii respond to localized temperature gradients across the host plant leaf? Adult B. argentifolii were placed in clip cages that were attached to the abaxial surface of cotton, Gossypium hirsutum L., and cucumber, Cucumis sativus L., leaves. A temperature gradient was created by either heating or cooling one side of the leaf with water-filled copper tubing placed on the adaxial leaf surface. Minimum and optimum leaf temperatures for oviposition were 16 and 31 degrees C, respectively, and were independent of plant species. No thermal maximum was detected because oviposition occurred at the highest leaf temperature (43 degrees C). Even though oviposition occurred at high temperatures, a stronger than expected preference was shown for the cool side of the leaf temperature gradient. This was true even at lower than optimum temperatures. Thus, even though B. argentifolii appeared capable of reproducing at the highest temperatures commonly encountered in the southwest deserts, they preferred cooler microenvironments, even when temperatures were below optimum for oviposition rate. This response may serve to maximize total egg production by increasing adult longevity.