Now is the time to be on the lookout for the European pine shoot moth, Rhyacionia buoliana, and the Nantucket pine tip moth, Rhyacionia frustrana. Both can be serious pests in nurseries and Christmas-tree plantations in Illinois. They attack red, mugo, Scots, and Austrian pines; however, they generally prefer Austrian and mugo pines. The European pine shoot moth and the Nantucket pine tip moth cause the same type of plant injury. It is essential that spray applications be made before the larvae (caterpillar) bore into the growing shoot because, once they enter the growing tips, they are protected from insecticide applications 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. 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 are yellow needles near the tips of twigs and pitch near new bud clusters. Mined needles will 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 appear reddish due to the presence of many dead tips. 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 2 to 3 millimeters long, turn deep black in color and are covered with resin-coated webbing. European pine shoot moth has only one generation per year. Nantucket pine tip moth has a life cycle similar to European pine shoot moth.
Management of European pine shoot moth and Nantucket pine tip moth involves pruning or using pest-control materials. Normal shearing (pruning) of Christmas trees in mid-July provides some measure of control in Christmas-tree plantations. Pest-control materials recommended for managing both the European pine shoot moth and Nantucket pine tip moth include acephate (Orthene), dimethoate (Cygon), and phosmet (Imidan). Spray applications should be made before larvae enter the growing shoot, which is normally in late June, or when hills-of-snow hydrangea 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 from both pests.