G. Thurston, C. Lucarotti, and E.G. Kettela
SERG Project #2001/07
Several products based on Bacillus thuringiensis (B.t.) (Foray 96B®, Dipel Wettable Powder VBC600004®, Bioprotec XHP® and HP®, and Thuricide 76LV® and one preparation of the eastern hemlock looper virus (Lafifivirus)) were aerially applied against larval eastern hemlock looper, Lambdina fiscellaria fiscellaria in western New Brunswick. All B. t. products were applied at the same rate. Product efficacy was assessed by monitoring larval numbers in the field at intervals after the spray and by conducting laboratory bioassays with treated foliage collected from the aerial spray blocks after product application.
The results from the field larval counts were variable due to the behaviour of the insect and the relatively low population density in the research area. Clear differences in efficacy were not observed. However, clear trends of decreasing population were visible, with the quickest reductions occurring in the blocks treated with the highest potency B.t. products.
The bioassay results clearly demonstrated the better efficacy of the BI products with the highest potencies. The lab results, combined with the field data and empirical field observations, indicate that all the B.t. products are effective against eastern hemlock looper larvae, with the best products being those with the highest potencies.
The virus was effective at killing larvae in the bioassay and in the field but was very slow in acting. This product may be useful in the tactic of initiating epizootics, should further monitoring of the virus block indicate its suitability for this purpose.