Jack pine budworm
Jack pine budworm larval surveys were completed in Northwest Region in Jack pine stands that have historically had budworm caused defoliation. Trees were sampled earlier than normal this year due to early development of male cones where young budworm larvae feed. No significant numbers of larvae were found and no defoliation had been observed by June 10, 1998. Egg mass surveys will be carried out later this summer.
The timing of larval surveys were three to four weeks ahead of last year. The effect of our El Nino spring played a major role in changing the timing of insect emergence this spring. In Region 1, larval surveys indicate that budworm numbers and defoliation were greater in 1998 than in previous years. Many of the stands have had heavy defoliation for more than six years and appear somewhat stagnated. One stand in Cass County, Sec. 21-T145-R30W has severe defoliation again this year following considerable top killing and whole tree mortality due to past years of defoliation and stress.
In Region 2, approximately 60 to 70 percent of the budworm had pupated by June 16th in St. Louis County near Ely. On June 23rd moth flight was well underway in northwestern St. Louis County. Very heavy defoliation occurred in northwestern St. Louis and eastern Koochiching Counties. Heavy rains have knocked many of the damaged needles off the trees making damage appear less than actually occurred. Near Linden Grove in west central St. Louis County, 50% of the moths emerged as of June 22nd. In general, balsam fir suffered heavy defoliation as did the white spruce, but defoliation was spotty. Several stands were only lightly or moderately defoliated.
In Region 3, very little damage occurred in white spruce plantations and natural stands in Morrison and Crow Wing Counties. Perhaps with the warm spring, needles and shoots became lignified earlier and were unpalatable to the caterpillars.