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European Pine Shoot Moth

June 10, 2003
European pine shoot moth, Rhyacionia buoliana, can be a serious pest in nurseries and Christmas-tree plantations in Illinois, attacking red, mugo, Scots, and Austrian pines; however, European pine shoot moth prefers Austrian and mugo pines. Repeated infestations can distort trees and reduce marketability. It is essential that spray applications be made before the larvae or caterpillar tunnel into the growing shoot because, once they enter the growing tips, they are protected from any insecticide application and are very difficult to kill.

In early spring, overwintered European pine shoot moth larvae crawl onto new shoots and tunnel into the base of buds or shoots. They eventually undergo a pupal stage within the shoot. In late May to early June, the European pine shoot moth adult female lays small, flattened eggs on new pine shoots near the base of needles or bud scales during a 2- to 3-week period. These eggs hatch in early to mid-June into larvae that tunnel into the needle sheaths and then mine needles at or near the base. Early injury symptoms include yellow needles near the tips of twigs and masses of pitch near the base of new bud clusters. Mined needles eventually turn brown and die. The larvae can kill terminal and lateral growth, due to their tunneling into the base of needles, shoots, or buds. Trees may eventually appear reddish due to the presence of many dead tips. In addition, European pine shoot moth larvae commonly cause the candle to die in a “shepard’s crook” shape. In nurseries and landscapes, small trees may be killed. In Christmas tree plantations, repeated infestations may leave trees appearing distorted, unsightly, and possibly unmarketable. Resin-coated webbing may be present near wounds or entry sites. In late summer to early fall, the larvae discontinue feeding for the growing season. They overwinter in needles near shoot tips that were mined during the summer. The larvae, which are 1/12 to 1/8 inch long, turn deep black in color and are covered with resin-coated webbing. European pine shoot moth has only one generation per year.

Management of European pine shoot moth involves pruning or using the insecticides permethrin (Astro, Pounce) or phosmet (Imidan). Normal shearing or pruning of Christmas trees in mid-July provides some measure of control in Christmas-tree plantations. Insecticides recommended for managing European pine shoot moth should be applied before larvae enter the growing shoot, which is normally in late June, or when hills-of-snow hydrangea (Hydrangea arborescens ‘Grandiflora’) is in early bloom. Concentrate sprays on the ends of branches where the larvae are most likely to be located.

Pheromone traps, which are used to monitor for male moth activity, can be used to help time spray applications. Spray 7 to 10 days after peak trap catch. Be sure to irrigate trees during periods of extended drought as dry weather and poor soil conditions may lead to increased susceptibility to attack.

Author: Raymond A. Cloyd


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