SERG Project # 1995/07 (2001)
The work conducted in these trials was undertaken in 2001 at the request of AEF Global with the objective of developing data in support of registration for Bioprotec XHP and Bioprotec HP for use against the spruce budworm, Choristoneura fumiferana. This project involved the testing of a new high potency Bacillus thuringiensis (Bt) product, Bioprotec XHP, and a comparison with Bioprotec HP and a registered Bt product, Foray 48B. The study area was located between Sudbury and North Bay, Ontario, and was selected because it is largely crown forest, had moderate to severe defoliation, and branch samples that yielded high numbers of apparently healthy, living second-instar budworm larvae.
Three blocks were treated with Bioprotec XHP (60 ha at 30 BIU/ha), 6 blocks with Bioprotec HP (60 ha at 30 BIU/ha and 60 ha at 15 BIU/ha), and one block with Foray 48B (50 ha at 30 BIU/ha). Three unsprayed control sites with spruce budworm larval populations similar to those in treated areas were selected for comparison purposes.
The percentage reduction in survival due to spray treatment was highest in the Bioprotec XHP (30 BIU/ha) blocks, next highest in the Bioprotec HP (15 BIU/ha) blocks, lower in the Bioprotec HP (30 BIU/ha) blocks, and lowest in the Foray 48B (30 BIU/ha) block. This result, however, is not reflected in the assessments of defoliation.
Defoliation estimates were determined by use of the Webb three-crown-level method. In all cases, defoliation in the upper crown and mid-crown areas was significantly lower in the treated sites than in the unsprayed controls. The Foray 48B and Bioprotec XHP and HP all yielded similar and acceptable levels of foliage protection. More defoliation was detected in the lower portions of the crowns of all trees, including the unsprayed controls. In the case of the treated sites, this reflects the filtering out of the spray cloud by the upper tree crown, which had very little damage.
The impact of the treatments on generation survival was determined by sampling for spruce budworm egg masses in July and August, 2002. This showed that the egg mass densities in the control sites were significantly different and higher than in the Bioprotec and Foray 48B treatments.