Natural Resources Canada, Canadian Forest Service,Laurentian Forestry Centre
Leo Cadogan and Arthur Retnakaran
Natural Resources Canada, Canadian Forest Service Great Lakes Forestry Centre
SERG Project #1999/05
Year of Project: 2000
Report Received: 2005
Tebufenozide (Rohm & Haas Co., Philadelphia PA) was applied aerially in Manitoba on June 3rd 2000 against spruce budworm (SBW) populations between the 4th and 5th instars (L5 treatments). It was also applied while most SBW were in the pupal stage (at the onset of the male moth flight season) to determine the impact of Mimic® on 1st and 2nd instars (L1 treatments). We found a highly significant influence of deposit (expressed in droplets/cm² on Kromekote cards) on population survival when applied against L5. Mimic® caused up to 94% mortality within < 30 days with a deposit of 3.533 droplets/cm² We could not demonstrate effective foliage protection with the L5 applications because of unexpectedly low defoliation in one of the control plots and low deposit in one of the treatment blocs. The most striking effect of Mimic® applied against the L5 was a 10 × depression of apparent fecundity in the treated plots compared to the controls. The causes of this reduction of oviposition in treated stands are not presently understood. There was no such reduction in populations when Mimic® was applied during the pupal stage, ruling out a direct effect on moths. In the season following treatment (2001), larval populations and defoliation in the L5 treatments were much lower than in the controls or in the blocs treated at the L1. The density of eggs at the end of 2001 was significantly lower in the plots treated at the L5 in 2000 than in the other plots (controls or those treated in the L1), an indication that the carry-over effect of Mimic® may last as much as two years. We detected no effect of Mimic® on population density, survival or defoliation when the product was applied against L1. While the lack of effect of the product against L1 is unequivocal, the results obtained with treatments against the L5 indicate a pronounced carry-over effect. Because the conclusions of this study are based on a small number of treatment replicates (3), tests focusing on the carry-over effect of L5 applications should be repeated, and an effort to explain the very low apparent fecundity of L5-treated populations should be made.