Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2003
Publication Date: 3/22/2003
Citation: Williams Iii, L.H., Logarzo, G.A., Shaw, S.R., Price, L.D., Manrique, V. 2003. Leiophron argentinensis shaw (Hymenoptera: Braconidae): a new species of parasitoid from Argentina and Paraguay, with information on life history and potential for controlling lygus bugs (Hemiptera: Miridae). Annals of the Entomological Society of America. Interpretive Summary: The tarnished plant bug is a serious pest of many crops, including cotton, in the United States. From 1999 to 2001 we conducted foreign exploration to find new beneficial insects that can be used to control plant bugs in crops in the United States. We discovered an undescribed species of beneficial insect attacking plant bugs in Argentina and Paraguay; this insect is described as Leiophron argentinensis Shaw. This insect has several attributes that indicate it has potential for controlling plant bugs in the United States. First, this insect was reared from plant bugs infesting several host plants already present in the U.S. Using a conservative measure of impact, rates of attack on plant bugs were as high as 37%. Attack levels were highest in the summer when crops are grown. Leiophron argentinensis was collected throughout the study area (~22 to 35°S latitude), corresponding to the crop production region in the southern U.S., although the insect may be effective in northern latitudes as well. Finally, the climate in the study area in South America was similar to that in the southern U.S., suggesting that this insect would survive if released here. In laboratory trials, L. argentinensis readily attacked the two most pestiferous plant bugs in North America, the tarnished plant bug and the western tarnished plant bug. Our results suggest that L. argentinensis has potential as a biological control agent for these pests in the United States.
Technical Abstract: We discovered an undescribed species of Leiophron parasitizing mirid nymphs in Argentina and Paraguay; this euphorine braconid is described as Leiophron argentinensis Shaw n. sp. Wasps were reared from several mirid species collected on numerous host plants, but most parasitoids (>85%) were reared from Taylorilygus apicalis (Fieber), which was the most abundant mirid. Parasitism rates ranged from 0-37%, and averaged ~7% for the entire study. Excluding samples where parasitism was not observed, parasitism rates averaged ~9%. Parasitism levels were highest in the summer. Host plant species significantly influenced parasitism levels of T. apicalis; nymphs on Conyza spp. suffered ~16% parasitism, significantly more than nymphs on other host plants. Leiophron argentinensis was collected throughout the study area (~22 to 35°S latitude), although the entire geographic range of this species is not yet known. We observed a transition from a male-biased sex ratio in the summer to a female-biased sex ratio in the fall. Leiophron argentinensis has several generations per year, and apparently produces some diapausing individuals in each generation. The incidence of diapause was lowest in the summer (~40%). In laboratory trials, L. argentinensis readily parasitized Lygus lineolaris (Palisot de Beauvois) and Lygus hesperus Knight, suggesting that L. argentinensis has potential as a biological control agent for these pests in the United States.