Effects of pesticides on Thomsonisca typica MERCET and Arrhenophagus chionaspidis GIRAULT, parasitoids of Pseudaulacaspis pentagona (Targioni)
2006
Yoshioka, T.(Fukuoka-ken. Agricultural Research Center, Chikushino (Japan)) | Takeda, M.
Effects of pesticides on Thomsonisca typica MERCET and Arrhenophagus chionaspidis GIRAULT, the main natural enemies of Pseudaulacaspis pentagona (Targioni), were evaluated under laboratory conditions. The pesticidal activities of 15 pesticides on the adult females of T. typica were investigated with a dipping method using tea branches for contact toxicity, and those of 13 pesticides on the adults of A. chionaspidis were also investigated in each sex. In addition, the numbers of A. chionaspidis, developed to the pupal or adult stage and reared on pumpkin fruits, were investigated when exposed to pesticides during their parental stages by way of dipping tea branches in pesticides for 24 hours. Methoxyfenozide and emamectin benzoate were found to be slightly harmful on the two species of parasitoids. Spinosad had no effect on the number of progeny of A. chionaspidis, while methoxyfenozide had small effect. Stronger harmful effects on reproduction were observed with the application of other pesticides; and, it was found that none of the progeny reached the pupal or adult stage when clotianidin, acetamiprid, and emamectin benzoate were applied. And, no significant correlation was found between the survival rate of the adults and the number of progeny with the application of these pesticides. Thus, it is necessary to examine not only the pesticidal activity on the adults but also the reproductive potential of the parasitoids when choosing pesticides with small effects on indigenous natural enemies.
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