TEMPERATURE-DEPENDENT DEVELOPMENT OF 3 HYMENOPTEROUS PARASITOIDS OF APHIDS (HOMOPTERA, APHIDIDAE) ATTACKING CITRUS

Aphids attacking citrus can he serious pests when they transmit severe strains of citrus tristeza virus. As part of an environmental assessm ent of exotic parasitoids of aphids, we compared the thermal relations hips of Aphelinus spiraecolae Evans & Schauff and Aphelinus gossypii T imberlake with the indigenous parasitoid, Lysiphlebus testaceipes (Cre sson), on the black citrus aphid, Toxoptera aurantii (Boyer de Fonscol ombe), in growth chambers in Florida. Overall, L. testaceipes developm ent time was shorter than that of the aphelinids ranging from 18.7 to 42.5% less throughout the range of temperatures tested (15-30 degrees C). Development times between the aphelinids were similar except at 15 degrees C where A. spiraecolae required 3.5 d more than A. gossypii. Developmental thresholds and degree-day requirements for L. testaceipe s were 7.5 degrees C and 212.8 DD; for A. spiraecolae were 7.9 degrees C and 294.1 DD; and for A. gossypii were 6.7 degrees C and 312.5 DD, respectively. Pupal mortality of L. testaceipes increased greatly at 2 7 degrees C and above, ranging from 24.8 to 44%; whereas mortality of the aphelinids remained low, ranging from 9.1 to 10.2% for A. sptraeco lae, and 13.3 to 15.8% for A. gossypii. Based on these relationships, we anticipate that these parasitoids can coexist and that different th ermal tolerances should broaden their potential as natural enemies of aphids attacking citrus.