if 
ei 
- F-493841, 493467 
Figure 51.—European pine shoot moth, Rhyacionia 
buoliana: A, red pine tip with solidified resin mass 
broken open to show partly grown larvae; B, red pine 
stand badly damaged by the shoot moth. Note spiked 
and bushy tops. 
or shoot. Larvae reach maturity in May, and pupation occurs inside the burrow in 
late May or June. From 2 to 3 weeks later, the larva works its way out of its 
chamber. There is one generation every 12 months, but occurring in 2 consecutive 
years. 
The most important and permanent damage to trees results from spring feeding. 
The killing of terminal and lateral buds results in dead, spike tops. The develop- 
ment of adventitious buds below this dead portion often causes the formation of 
dense, bushy growth the following season. The killing of the terminal bud and the 
development of several lateral buds into competing leaders results in forked stems. 
Shoots weakened by larval tunneling may fall over, but continue to grow. This. 
results in the formation of crooked trunks and branches called “post horns.” All 
open-grown young trees of susceptible species below a height of 6 to 8 m are subject 
to attack and damage. Taller trees or trees growing in closed stands are usually not 
seriously damaged. Also young trees having adequate soil moisture during early 
summer are not damaged; apparently the needlemining larvae are “pitched out.” In 
Ontario this insect often destroys second-year pine cones on young trees and on the 
lower branches of larger trees (760). 
Climate is an important factor affecting the distribution and abundance of the 
European pine shoot moth. Overwintering larvae are killed by temperatures colder 
than about — 29° C. Warm, dry summers followed by mild winters permit max- 
imum survival. Rate of tree growth is also important as damage is usually most 
severe on slow-growing trees. Introduced and native species of parasites normally 
destroy about 10 percent of the population. Several species of parasites introduced 
to North America have become established, and two of these species, Orgilus 
obscurator (Nees) and Lypha dubia Fallén, appear to be most successful. Refer- 
ences are available for more complete information on arthropods attacking Rhya- 
cionia spp. (526, 788, 1184, 1363). 
The planting of susceptible pines on good sites, ““snow-depth pruning,” and 
Christmas tree shearing are helpful in reducing damage (552). Fumigation in the 
spring has provided a degree of control on seedlings and larger ornamental spec- 
imens (197). 
Many reports have been issued on the biology, ecology, and control of the 
European pine shoot moth. In addition to those cited in preceding paragraphs, there 
150 
