Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/13/2012
Publication Date: 2/28/2013
Citation: Fuentes-Contreras, E., Figueroa, C.C., Silva, A.X., Bacigalupe, L.D., Briones, L.M., Foster, S.P., Unruh, T.R. 2013. Survey of resistance to four insecticides and their associated mechanisms in different genotypes of the green peach aphid (Hemiptera: Aphididae) from Chile. Journal of Economic Entomology. 106:400-407. Interpretive Summary: The green peach aphid, GPA, is a major pest of agriculture worldwide especially because of the many plant diseases it transmits and its propensity to rapidly evolve resistant to insecticides. There is concern that insecticide resistance is developing in potato-infesting populations of GPA in Chile. USDA researchers at ARS Yakima Agricultural Research Laboratory, Wapato, WA, in collaboration with Chilean and British researchers, estimated the number of genetically unique populations of GPA in Chile and sought evidence for insecticide resistance in those populations. Using seven microsatelite genetic markers from 50 population isolates they found nine genetically distinct isolates. Among those were two isolates that showed genetic mutations (modified cholinesterase) which imparted >20 fold resistance to pirimicarb, a carbamate insecticide. Other genetic mutations that impart modest resistance of less than 10 fold were seen for genes that detoxify organophosphate, pyrethroid, and neonicotinoid insecticides suggesting they were unlikely to pose control failure problems in the near term. However, mild cross-resistance between the neonicotinoid insecticide, imidicloprid, with organophosphates, suggests that imidicloprid should be used carefully to prevent the evolution of resistance to this important new pesticide.
Technical Abstract: The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) is a major pest of agriculture worldwide that is particularly adept at evolving insecticide resistance very frequently develop insecticide resistance. Seven mechanisms that confer resistance to many insecticide types have been described in M. persicae. We surveyed the resistance status of aphids from this species collected on different crops and weeds along a 1,830 Km transect in Chile. Fifty multilocus genotypes (MLGs) were identified using microsatellite markers, and these MLG clonal populations were evaluated for the presence of modified acetylcholinesterase (MACE), kdr and super kdr mutations and enhanced carboxyl esterase activity. Toxicological bioassays were used to estimate aphid LC50 when treated with metamidophos (organophosphate), pirimicarb (dimethyl carbamate), cyfluthrin (pyrethroid) and imidacloprid (neonicotinoid). Two MLGs presented > 20 fold resistance to pirimicarb, which was associated with the MACE mutation in the heterozygous condition. The kdr mutation was found in only four MLGs in the heterozygous condition and they showed resistance ratios (RR) to cyfluthrin of less than seven fold. The super kdr mutation was not detected. Enhanced carboxyl esterase activity was predominantly found in the susceptible (S) to first level of resistance (R1) with RR to metamidophos less than eight fold. Finally, RR to imidacloprid was also less than eight fold in all MLGs tested. A few MLGs with resistance to pirimicarb were found, while susceptibility to cyfluthrin, metamidophos and imidacloprid was still predominant. A significant positive correlation between imidacloprid tolerance with pirimicarb resistance was detected, as well as between imidicloprid and metamidophos tolerance. With the increase in the use of neonicotinoid insecticides, better rotation of insecticides with different modes of action will be necessary to prevent further development of M. persicae insecticide resistance in Chile.