Abstract
Aphids attacking citrus can be serious pests when they transmit severe strains of citrus tristeza virus. As part of an environmental assessment of exotic parasitoids of aphids, we compared the thermal relationships of Aphelinus spiraecolae Evans & Schauff and Aphelinus gossypii Timberlake with the indigenous parasitoid, Lysiphlebus testaceipes (Cresson), on the black citrus aphid, Toxoptera aurantii (Boyer de Fonscolombe), in growth chambers in Florida. Overall, L. testaceipes development 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. testaceipes 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 27 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. spiraecolae, and 13.3 to 15.8% for A. gossypii. Based on these relationships, we anticipate that these parasitoids can coexist and that different thermal tolerances should broaden their potential as natural enemies of aphids attacking citrus.
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