Comparing the efficacy of various aerial spraying scenarios using Bacillus thuringiensis to protect trees from spruce budworm defoliation

•We evaluated five different Btk spraying scenarios to protect host trees from spruce budworm.•We hypothesized that less frequent Btk application could protect trees at a lower cost.•Black spruce maintained at least 54% of its residual photosynthetic capacity (RPC), even without protection.•Btk application every 2 years seems to be a relevant alternative to protect balsam fir and white spruce.•This scenario kept RPC above 39% and required 36% fewer applications over 7 years.