Yearbook^ of Agriculture 1949 



SPRUCE BUDWORM SITUATION 



1948 



Serious tree mortality 

 Medium to heavy defoliation 

 Light defoliation 



Plots and experimental areas were es- 

 tablished in the Northeast to determine 

 the degree of defoliation and damage 

 caused under different forest condi- 

 tions. In the Rocky Mountains there 

 are several species of parasites of the 

 budworm that do not occur in the East ; 

 several colonies of those parasites were 

 obtained and released in eastern for- 

 ests in the hope that they would be- 

 come established. 



THE SPRUCE-FIR STANDS in the 

 Adirondacks, relatively small in area, 

 usually are surrounded by hardwoods. 

 Such stands seem particularly favorable 

 for natural control. Winter mortality 

 during 1946-47 was approximately 75 

 percent. Aggregate parasitization by in- 

 sect enemies ranged from 64 to 86 

 percent in different area. The total 

 aggregate mortality from winterkill and 

 parasites ranged from 83 to 98 percent. 

 Insectivorous birds also destroyed large 

 numbers of budworm larvae and pu- 

 pae. Certainly those factors of natural 

 control contributed tremendously in 

 bringing about the decline in budworm 

 infestation in 1947 in New York. 



THE SEASONAL HISTORY of a pest 

 must be known before control meas- 

 ures can be undertaken. 



The adult of the spruce budworm is 

 a small moth with a wing spread of 

 seven-eighths of an inch. Its general 

 color is grayish with brown markings. 



In the Northeastern States the moths 

 start emerging from their pupal cases 

 about July 1 . The females deposit their 

 pale-green eggs on the foliage in masses 

 of 10 to 50 or more, where they overlap 

 like the scales of a fish. One female 

 may lay several of these egg masses 

 and on the average produces about 175 

 eggs. The incubation period lasts about 

 10 days. 



After the eggs hatch, the young cat- 

 erpillars crawl about until they find 

 suitable places under bark or bud scales 

 to spin silken weblike coverings, or 

 hibernacula, under which they spend 

 the following fall and winter. These 

 tiny larvae do not feed until they be- 

 come active in late April or early May 

 and leave their hibernacula. At first 

 they are an orange yellow; later they 

 turn brownish. They mine the old nee- 

 dles first; then they enter the opening 



