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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Publications at this Location » Publication #202632

Title: Intraguild predation on Eretmocerus nr emiratus, a parasitoid of Bemisia tabaci by three generalist predators with implications for estimating the level and impact of parasitism.

Author
item Naranjo, Steven

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2007
Publication Date: 6/1/2007
Citation: Naranjo, S.E. 2007. Intraguild predation on Eretmocerus nr emiratus, a parasitoid of Bemisia tabaci by three generalist predators with implications for estimating the level and impact of parasitism.. Biocontrol Science and Technology. 2007; 17(5/6): 605-622.

Interpretive Summary: Intraguild predation (IGP) occurs when two natural enemies competing for the same prey attack and consume one another. IGP is widespread in agricultural systems may have negative, neutral or positive effects on the biological control of pest insects. Both generalist predators and aphelinid parasitoids attack sweetpotato whitefly on cotton in the southwestern US. A series of laboratory experiments were conducted to quantify prey consumption patterns and preference by three representative generalist predators, Geocoris punctipes, Orius insidiosus, and Hippodamia convergens, offered 4th stage B. tabaci nymphs and hosts parasitized by Eretmocerus nr. emiratus. All three predators showed a significant preference for larval and pupal stage parasitoids over early 4th instar nymphs, but G. punctipes and O. insidiosus attacked parasitized and non-parasitized prey equally when offered a choice of larval parasitoids and late 4th instar nymphs. This behavior has consequences for both the calculation of parasitism and its impact on pest populations in the field. Further analysis showed that altering the estimation of parasitism by accounting for preference had a very small positive effect (0.02-1.13 % change) on total generational mortalities observed in previous field life table studies. Likewise, accounting for IGP on parasitoids had only small negative effects on total generational mortalities (0.193 – 1.278 % change). Thus, IGP would not be expected to impact the overall biological control of whitefly in cotton.

Technical Abstract: Intraguild predation is pervasive in many managed and unmanaged ecosystems. Both generalist predators and aphelinid parasitoids attack Bemisia tabaci on cotton in the southwestern USA. Free-choice and no-choice laboratory assays were conducted to quantify prey consumption patterns and preference by three representative generalist predators, Geocoris punctipes, Orius insidiosus, and Hippodamia convergens, offered 4th stage B. tabaci nymphs and hosts parasitized by Eretmocerus nr. emiratus. All three predators showed a preference for larval and pupal stage parasitoids over early 4th instar nymphs, but G. punctipes and O. insidiosus were non-discriminating when offered a choice of larval parasitoids and late 4th instar nymphs. Total daily prey consumption was generally the same in free-choice and no-choice arenas and averaged 18.9, 5.8, and 17.0 for G. punctipes, O insidiosus and H. convergens, respectively. Preference for parasitized hosts alters the methods required for calculating marginal rates of parasitism in the field. However, incorporating a preference variable in the estimation procedure had a very small positive effect (0.02-1.13% change) on total generational mortalities observed in previous field life table studies. Likewise, although intraguild predation was demonstrated in this experimental system the implications for biological control are unclear. Accounting for intraguild predation had only small negative effects on total generational mortalities (0.193 – 1.278% change).