Predation by Solenopsis invicta and Blattella asahinai on Toxoptera citricida parasitized by Lysiphlebus testaceipes and Lipolexis oregmae on citrus in Florida

Abstract

Predation by two generalist predators, the red imported fire ant, Solenopsis invicta, and the Asian cockroach, Blattella asahinai, on parasitoids of the brown citrus aphid, Toxoptera citricida, was investigated in the laboratory and in a citrus grove in Florida. Females of the parasitoids Lipolexis oregmae and Lysiphlebus testaceipes were equally efficient at avoiding ants (at distances <2 mm) during oviposition attempts in the laboratory, but significantly fewer aphids were parasitized by both parasitoid species. In field trials, however, no significant differences in parasitism rates were observed when lower densities of fire ants were present. Workers of red imported fire ants selectively removed aphids from citrus trees parasitized by both parasitoids, with most taken 2–3 days after aphids were exposed to parasitoids in both the laboratory and field trials. Significantly fewer parasitoid progeny were produced by both parasitoid species if S. invicta was present due to selective predation on aphids containing immature parasitoids, suggesting that S. invicta has a negative effect on parasitoid efficacy. Percentage eclosion of adult parasitoids was not significantly different if B. asahinai was present, but starved (24 h) B. asahinai consumed or severely damaged young and mature mummies of T. citricida containing both parasitoid species, resulting in no adults emerging in any trial. These data indicate that S. invicta is a potential disruptor of L. oregmae as a classical biological control agent of T. citricida while, unless starved, B. asahinai poses a lesser threat.