Insecticide susceptibility of variegated cutworm 



JESO Volume 139, 2008 



plastic containers (34 x 25 x 13 cm) filled with 5 cm sterilized sandy loam. Chinese cabbage, 

 Brassica rapa L. (Brassicacaeae), was provided as food. Larvae were fed 3 times a week 

 and dry, rotten or moldy food materials were removed. Pupae were collected and placed 

 in adult cages made of 11 L ice cream buckets with a screened opening (15 x 10 cm) in 

 the side. Red Gatorade* and deionized water were used as food and moisture sources. A 

 piece of red tissue paper (20 x 20 cm) was crumpled and placed in the container for use as 

 an oviposition site. Pieces of tissue paper with egg masses attached were placed on 9 cm 

 diameter filter paper in 10 cm diameter Petri dishes with a commercial VCW artificial diet 

 (Southland Products Inc., Lake Villages, AK) cube (0.5 cm 3 ) Rearing cages were kept in 

 growth chambers set at 23 ± 2°C, 60-70% RH and 16:8 L:D. 



Insecticide Assays 



Direct contact toxicities of technical grade (> 95% purity) permethrin (FMC 

 Corp., Philadelphia. PA), chlorpyrifos (Dow AgroSciences Canada, Inc., Calgary, AB), 

 methomyl (E.I. DuPont Canada Co., Mississauga, ON), lambda-cyhalothrin (Syngenta 

 Crop Protection Canada, Inc., Guelph, ON), chlorantraniliprole (E.I. DuPont Canada 

 Co., Mississauga, ON), , spinosad (Dow AgroSciences Canada, Inc., Calgary, AB) and 

 metaflumizone (BASF Canada, Inc., Mississauga, ON) to VCW larvae were determined 

 using a Potter spray tower (PST) (Potter 1959) following the procedure described by Harris 

 et al. (1977). Primary screening tests were done with 4 concentrations of the insecticide 

 dissolved in 19:1 acetone:olive oil. Controls treated with the solvent mixture alone were 

 included with each insecticide. Two groups of 10, 3rd-4th instar larvae were tested at each 

 insecticide concentration. Each bioassay was repeated 3 times resulting in 60 treated larvae 

 per concentration. Larvae were transferred with a fine paint brush to a clean 10 cm diameter 

 glass Petri dish lined with 9 cm diameter filter paper. Five ml of the desired concentration 

 of each insecticide was then applied to each dish via the PST. Immediately after treatment 

 the larvae were placed in waxed paper Dixie- cups (10/cup) filled with 1 cm sifted sandy 

 loam and two commercial VCW artificial diet cubes (0.5 cm 3 ) were provided as food. Cups 

 were covered with a 10 cm diameter glass Petri dish and were placed in a holding room at 

 25 ± 1°C and 16:8 L:D. Mortality counts were made after 48 h. Larvae were considered 

 dead if unable to crawl. Second and 5th instar larvae also were tested to determine the 

 susceptibility of the different larval stages to pyrethroids. Corrections for natural mortality 

 (< 10%) were made using Abbott's formula (Abbott 1925). 



Results 



Flight Activity 



In 2006, there were 2 peaks of adult activity in Norfolk County in July and August. 

 Populations dropped to low levels in mid-August remaining that way until the study was 

 terminated in mid-September (Fig. 1). There were 3 smaller peaks of adult activity in July. 

 August and September in Essex County (Fig. 1). 



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