The European Pine Shoot Moth -- Ecology and Control in the Lake States
Abstract:The European pine shoot moth, Rhyacionia buoliana (Schiff.), now firmly established in northeastern North America, distorts growth of red pine (Pinus resinosa Ait.) and many other pines by feeding on buds and shoots. Pine species differ in susceptibility to attack and ability to recover from injury. Infested leaders are not necessarily damaged; the center bud may survive to elongate normally. The worst damage results when heavy infestation causes the top whorl to lose dominance to a branch lower on the stem. The origin of "crooks", "forks", "pruning", "bushes", and "spike-tops" is explained by timing and extent of larval feeding. On dominant whorls, the frequency of crooks and extent of other injuries are correlated with insect population level and tree size. Damage tends to be corrected in time. Most eggs are laid singly on the bark of current-growth shoots at all heights in young trees. In the spring larvae crawl upward, increasing the number of insects in the tops of trees where tips are fewer. The number of larvae inhabiting a leader is related to the number of larvae on the tree. The intertree distribution of larvae departs from randomness toward aggregation; this aggregation declines as the generation progresses. For rapid survey purposes, proportion of leaders or trees infested may be used to estimate overall population. At low to moderate population levels in summer, number of injured tips is similar to number of larvae. Life tables based on six intervals of the life cycle showed that population trend correlated best with survival during winter. Winter survival can be greatly influenced by depth of snow and tree height. Late-generation survival can be affected by numbers of tips when ratios of insect numbers to tip numbers are high. The potential of several suppression and control approaches for altering population trend is considered. Snow-depth pruning--the removal of branches near the ground--lessens winter survival and may be a useful one-time control measure.
Document Type: Journal Article
Publication date: June 1, 1967
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