about factors tending to hold populations in check during intervals between out- 
breaks or which assist in bringing them under control once they are underway (/27, 
882). 
The spruce budworm has many natural enemies, including parasites and preda- 
tors, birds, mites, spiders, and several pathogenic organisms. Their effectiveness in 
control is always important, but it is greatest only after another agent, such as 
weather or starvation, has reduced the budworm population considerably (548). A 
number of authors have evaluated the control effectiveness of natural enemies in 
specific outbreaks (/24, 126, 329, 330, 636, 787). 
Other important natural control factors affecting the spruce budworm are: (1) the 
loss of young larvae through competition for new foliage in heavy infestations; (2) 
loss of young larvae as a result of cooler than normal temperatures and late frosts in 
the spring; (3) loss of large larvae through starvation following complete defolia- 
tion; and (4) loss of adults through dispersal. 
A number of management practices have been suggested for reducing the 
chances of spruce budworm outbreaks. These include the utilization of balsam fir 
(125, 1182); the regulation of age classes to prevent the occurrence of large areas of 
overmature fir (125, 498), and the favoring of less susceptible species, such as red 
spruce. Discussions that favor forest management oversimplify the special rela- 
tionships between the budworm and balsam fir (66). 
The removal of overstory mature balsam fir was suggested for preventing out- 
breaks (806, 1277); management plans and risk-rating systems for selective cutting 
were presented (807, SO8, 1278); and risk-rating systems for the Lake States were 
devised (69, 70, 78, 495). Publications on the budworm and forest management in 
the Maritime Provinces of Canada are available (46, /95). 
For further information on the spruce budworm, the reader is referred to reviews 
of the literature (66, 635, 797). 
The jack pine budworm, C. pinus pinus Freeman, is known to occur in Nova 
Scotia, Ontario, Manitoba, and from Michigan to Minnesota. Its hosts include 
various species of pine, especially jack and red. The adult has a wingspread of 
about 22 mm. The head, thorax, and forewings are ochreous-tawny; the forewings, 
distinctly maculate; and the hindwings smoky with dark basal lines through their 
white fringes. The full-grown larva has a shiny light-brown to black head, a dark- 
brown “‘collar” separated from the head by a narrow white band, a reddish-brown 
body with yellowish sides, and two rows of white dots along the back; it is about 21 
mm long (fig. 60). Pupae are pale green when just formed; later, they become dark 
reddish-brown, and they are about 12 mm long. 
Courtesy Can. For. Serv., Can. Dep. Environ., 
Sault Ste. Marie, Ont. 
Figure 60.—Larva of the jack pine budworm, 
Choristoneura pinus pinus, feeding on needles of jack 
pine. 
167 
