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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 #251889
Title: Compatibility of Two Systematic Neonicotinoids, Imidacloprid and Thiamethoxam with various Natural Enemies of Agricultural Pests.

Author
item PRABHAKER, NILIMA - University Of California
item Castle, Steven
item Naranjo, Steven
item TOSCANO, NICK - University Of California
item MORSE, JOSEPH - University Of California

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2011
Publication Date: 6/2/2011
Citation: Prabhaker,N., Castle,S.J., Naranjo,S.E., Toscano,N., Morse,J. 2011. Compatibility of two systematic neonicotinoids, imidacloprid and thiamethoxam with various natural enemies of agricultural pests. Journal of Economic Entomology. 104:773-781.

Interpretive Summary: Neonicotinoid insecticides are widely used in many agricultural and horticultural production systems to control a wide array of pest insects. While they have been touted as selective insecticides, mainly based on their systemic activity, they have not been widely tested against common natural enemy species found in arid-land production systems in the southwestern U.S. This study examined the impact of two insecticides, imidacloprid and thiamethoxam, on six species of beneficial arthropods including four parasitoid species, Aphytis melinus Gonatocerus ashmeadi, Eretmocerus eremicus, and Encarsia formosa, and two generalist predators, Geocoris punctipes and Orius insidiosus, in the laboratory using a systemic-uptake bioassay. All the parasitoid species were negatively affected by these insecticides, with the greatest negative affects observed for A. melinus, and important parasitoid of scales in citrus. The two predator species were variably susceptible to imidacloprid and thiamethoxam after 96 h exposure and toxicity may be related to exposure through both plant sap feeding and plant surface residues. These laboratory results contradict the notion of little impact of these systemic neonicotinoids on insect parasitoids or predators but further studies will be needed to better quantify the levels of impacts under field conditions.

Technical Abstract: Two systemic neonicotinoids, imidacloprid and thiamethoxam, are widely used for residual control of a number of insect pests in cotton, vegetables, and citrus. We evaluated their impact on six species of beneficial arthropods including four parasitoid species, Aphytis melinus Gonatocerus ashmeadi, Eretmocerus eremicus, and Encarsia formosa, and two generalist predators, Geocoris punctipes and Orius insidiosus, in the laboratory using a systemic-uptake bioassay. Exposure to systemically treated leaves of both neonicotinoids had negative effects on adult mortality of all four parasitoids, with higher potency against A. melinus as indicated by low LC50’s. Mortality also was high for G. ashmeadi, E. eremicus and E. formosa after exposure to both compounds, but only after 48 h post-treatment. The two predators, G. punctipes and O. insidiosus were variably susceptible to imidacloprid and thiamethoxam after 96 h exposure. However, toxicity to predators may be related to their feeding on foliage and not just contact through surface residues. Our laboratory results contradict suggestions of little impact of these systemic neonicotinoids on parasitoids or predators but field studies will be needed to better quantify the levels of such impacts under field conditions.