Long term dynamics of aphelinid parasitoids attacking Bemisia tabaci

Authors: Naranjo, Steven; LI, SHUJUAN - University Of Arizona

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2015
Publication Date: 2/1/2016
Citation: Naranjo, S.E., Li, S. 2016. Long term dynamics of aphelinid parasitoids attacking Bemisia tabaci. Biological Control. 93:56-64.

Interpretive Summary: The sweetpotato whitefly (Bemisia tabaci) is a major pest of multiple crops globally. In the southwestern US it attacks cotton and a number of vegetable crops. The insect is attacked by a number of natural enemies including several species of parasitoids. Here we describe and analyze the long-term dynamics of parasitoids, whitefly and their interactions that covers a period (1996-2010) during which there was a large classical (introductory) biological control program underway. Three native species of parasitoids were found attacking whiteflies in cotton fields in Arizona during the 1990’s. Around the early 2000’s these species became largely displaced by two exotic species of parasitoids that were release by the biological control program. One of these species has now become the single dominant parasitoid. Rates of apparent parasitism were highly variable within and between years and averaged ˜20% overall. In the vast majority of years there was no evidence of density dependence in rates of parasitism and thus no evidence that parasitoids are regulating whitefly populations. Correlations between changing pest density and parasitism over the 15-year period in cotton were weak or nonexistent and there was no evidence that these dynamics have changed since the establishment of the two exotic species. Overall, this study suggests that parasitoids contribute in only a minor way to whitefly population dynamics in cotton. Detailed life

Technical Abstract: Aphelinid parasitoids are widely known natural enemies of Bemisia tabaci, a serious pest of agriculture globally. Here we examine pest and parasitoid interactions and dynamics in cotton from 1996–2010, during which a classical biological control program was underway. Two native species, Eremocerus eremicus and Encarisa meritoria were largely or completely displaced by exotic Eretmocerus sp. (Ethiopia) and Encarsia sophia in the early 2000’s. Further, E. sophia has become the dominant parasitoid of B. tabaci in cotton after many years of dominance by native and exotic Eretmocerus. Rates of apparent parasitism were highly variable within and between years and averaged ˜20% overall. In the vast majority of years there was no evidence of density dependence in rates of parasitism. When density dependence was noted it was weak and either inversely dependent or directly dependent. Correlations between changing pest density and parasitism over the 15-year period in cotton were weak or nonexistent and there was no evidence that these dynamics have changed since the establishment of the two exotic species. Detailed life table studies will be needed to fully assess the impact of the classical biological control program.