Pine moth is a common species in whole Europe, except the United Kingdom. It is also observed in western part of Asia. In Poland its outbreaks usually occur in central and south-eastern parts of the country.
In Poland D. pini is one of the most harmful insect pests of the Scots pine. It prefers 30 to 60 year old stands growing in dry poor site conditions where precipitation does not exceed 600 mm. It sporadically can be observed on some other pines, e.g. the black pine, eastern white pine, mountain pine.
Adult female moths have a 8 cm wingspan. Male moths are with a 6 cm wingspan. A color of moths varies much from light-gray to brownish-black. The first pair of wings are with a small white spot and wide dark strip. Antennae of females are slightly saw-shaped, while those of males are double comb-shaped. An egg is oval 2 mm long gray or brownish-gray. Caterpillars are gray or brown, much hairy, with steel-blue bands without hair on the second and third segments and a V-shaped spot on the eight segment of the body. Fully developed caterpillars are 50-80 mm long. The pine moth overwinters as a black-brown 30 mm long pupa in a cocoon.
Moths fly after sunset from late-June through August. Single moths can be observed in the first days of June and in late-August. A female lays 150 to 300 eggs on branch and trunk bark, needles in aggregations of up to 100 eggs. Caterpillars hatch 2 weeks later. They first feed on egg shells, then on needles. In mid-October or early-November, just after the first strong autumn frost, the caterpillars descent to forest litter to overwinter. Most of them (about 85%) are located in a distance of about 1 m from tree trunk. In early spring, soon after snow melting, the caterpillars climb up to the tree crown, where they feed until July. They pupate in June, July and August in 5 cm long yellowish-gray spindle-shaped cocoons. Cocoons can be find in bark crevices, on needles and branches. Pupal stage lasts for about 4 weeks. D. pini is a monovoltine species, although some individuals feeding separately or in small groups require about 2 years to finish their development.
One pine moth caterpillar consumes about 1000 needles during its life time. Caterpillars often start feeding on the bark of young shoots after all needles are consumed. Feeding intensity depends on the caterpillar density. Caterpillars feeding in groups of 5 individuals feed more, grow faster, have lower mortality and are darker than those feeding individually. Caterpillars feed twice during their life time. They start feeding for the first time in late summer and end it in late autumn and for the second time in early spring and end it in June or July.
Stands preferred by the pine moth should be reconstructed into multi-species stands. Silvicultural measures should be done in time. Ant nests and birds should be protected. All of these activities should be done simultaneously.
Forecasting is based on autumnal searches of caterpillars in forest litter. In spring additional methods are used: counting caterpillars aggregated below glue band on tree trunks during their climbing up to tree crown or counting caterpillars in tree crown fell down on a sheet made of the strong material.
Biological and chemical insecticides can be used to control the pine moth.
- Kolk A., Starzyk J. R., 1996: The Atlas of Forest Insect Pests
(Atlas skodliwych owadów lesnych) - Multico Warszawa, 705 pages. Original publication in Polish. English translation provided by Dr. Lidia Sukovata and others under agreement with The Polish Forest Research Institute.