Insecticide susceptibility of variegated cutworm 



JESO Volume 139, 2008 



FLIGHT ACTIVITY AND SUSCEPTIBILITY TO INSECTICIDES 

 OF VARIEGATED CUTWORM, PERIDROMA SAUCIA (HUBNER) 

 ATTACKING FIELD TOMOATOES IN SOUTHWESTERN 



ONTARIO 



C. D. SCOTT-DUPREE 1 , C. R. HARRIS, M. MOINEDDIN, J. LEBOEUF 2 

 Department of Environmental Biology, University of Guelph, 

 Guelph, Ontario, Canada NIG 2W1 

 email: cscottdu@uoguelph.ca 



Abstract J. ent. Soc. Ont. 139: 19-25 



The variegated cutworm, Peridroma saucia (Hiibner), is a polyphagous 

 pest that sporadically damages processing field tomatoes in southwestern 

 Ontario. Recent anecdotal reports have suggested that it has developed 

 resistance to pyrethroid insecticides used to control them. The objectives of 

 this study were to acquire information on variegated cutworm flight activity 

 in southwestern Ontario tomato fields and to assess the toxicity of currently 

 registered and novel insecticides to determine if it has developed resistance 

 to them. 



Pheromone trap data (2006) in Norfolk County suggested 2 peaks of 

 adult flight in field tomatoes - July and August, while in Essex County 

 there were 3 peaks - July, August and September. Direct contact toxicity 

 bioassays were done using larvae from a laboratory culture established at 

 the University of Guelph in late summer 2006 from larvae collected from 

 tomato fields in both counties. Of the 4 insecticides registered for use, 

 lambda-cyhalothrin was most toxic to 3rd-4th instar larvae > permethrin > 

 chlorpyrifos > methomyl. Chlorantraniliprole was most toxic of the reduced 

 risk insecticides tested. Spinosad and metaflumizone, which act primarily 

 as stomach poisons, were less toxic by direct contact. Second instar larvae 

 were most susceptible to permethrin > 3rd-4th > 5th instar. Comparison 

 of results with 1977 published data showed that variegated cutworm had 

 developed low level resistance to methomyl but not to chlorpyrifos or 

 permethrin. Results of the study showed that pyrethroid insecticides will 

 be effective so long as stage of larval development and climatic conditions 

 are considered and insecticides are applied in a manner resulting in the most 

 effective penetration of the plant canopy as possible. 



Published November 2008 



1 Author to whom all correspondence should be addressed. 



2 OMAFRA, Ridgetown Resource Centre, 400 Main St. E., Ridgetown, ON, NOP 2C0 



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