Pine shoot moths
Click for larger image Curled growing tips on pine (Pinus) caused by larvae of European pine shoot moths (Lepidoptera). D. McComb, USFS, Bugwood.org

The European pine shoot moth, Rhyacionia buoliana is a very serious pest of mugo and red pines in ornamental plantings. Austrian, Scotch (Scots), and Japanese black pines also may be badly damaged. It was first observed in this country in 1913, attacking ornamental Scotch (Scots) pines on Long Island. Because of this insect, a federal quarantine prohibiting importing pines from Europe was established in 1915.

Larvae of several other species of small moths tunnel in the tips of pines wherever susceptible conifers are grown in the United States. The most damaging of these species also belong to the genus Rhyacionia.

Symptoms and Diagnosis

The damage inflicted by all species of Rhyacionia is similar: the tips of terminal and lateral shoots are killed as a result of larval boring, initially into the base of the needles or buds, and then into the shoot itself. Attacked buds can be stunted and tend to be coated with resin. Silk webbing is often present. Mining or tunneling may be difficult to find due to copious resin flow.

Early indications of attack are yellowing of needles near the tips of twigs and often clear deposits of pitch around and between new bud clusters. Later, dead buds and dead or deformed shoots result in striking deformity of the tree.

Life Cycle

In late July or early August for a period of several weeks, adult moths lay small, flattened eggs on new shoots near the base of the needles or bud scales. The young hatch and spin resin-coated webs between the needles and twigs where they bore into the base of needles and begin feeding. As the larvae grow they move to the buds where they continue to feed and then bore into the tips where they overwinter. The boring process causes a distinctive crust of resin to form, which can be diagnostic of the presence of pine shoot moth. The following spring the larvae emerge from hibernation and continue feeding until they pupate in May or June. During this spring period is when most damage occurs. There is one generation per year.

Integrated Pest Management Strategies

1. Maintain plant vigor. Dry weather and poor soil conditions encourage damage by tip moths; therefore, water during times of drought.

2. Select planting area carefully. Pine trees should be planted in well-drained soil that is slightly acid. Pines should not be planted in continually wet areas.

3. Prune. For small plantings or small trees, prune or handpick infected shoots and dispose of material, thus eliminating the larvae.

4. Insecticide. In early spring, spray with an insecticide and follow up with another application in late spring. Some of the chemicals that may be recommended are carbaryl (Sevin), trichlorfon (Dylox), cyfluthrin and pyrethrins.

Organic Strategies

Strategies 1, 2, and 3 are strictly organic approaches. For an organic approach to Strategy 4, consult the Organic Materials Review Institute (OMRI™) for appropriate pyrethrin products.

More images:

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Pine shoot moth caterpillars/larvae (Lepidoptera) on pine (Pinus). M. Zubrik, Forest Research Institute - Slovakia, Bugwood.org
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Adult pine shoot moth (Lepidoptera) on pine (Pinus). F. Stergulc, Universita di Udine, Bugwood.org
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Adult pine shoot moth (Lepidoptera). USFS - Northeastern Area Archive, Bugwood.org