Life History of the Western Pine Shoot Borer (Lepidoptera - Olethreutidae) and Effects on Lodgepole Pine in Central Oregon

1991

S. 206-211

1 Abb., 2 Tab., 12 Lit. Ang.

Unselbständiges Werk

200091793

The biology of the western pine shoot borer, Eucosma sonomana Kearfott, was investigated in young lodgepole pine (Pinus contorta Dougl.) from 1987 through 1989 in central Oregon. In the stands studied, 65-80% of the terminals were infested. Attacks were common on trees as small as 0.5 m tall, and infestation levels were high through the seedling and sapling stages. About 50% of the infested terminals contained two or more larvae. Symptoms of attack on lodgepole pine (short needles, short terminal shoots, dead shoots, and exit holes) were similar to those on ponderosa pine (P. ponderosa Douglas ex Laws.), but they were more subtle. Our observations suggest that exclusion of shoot borers increased the average height growth in two young lodgepole pine stands by (Formel) per year. At intermediate elevations for lodgepole pine (1,340-1,370 m), moth flight and oviposition began in April withthe accumulation of 55 degree-days (DD) above 5.5C and before terminal growth on lodgepole pine had begun. The first larvae appeared in May at 240 DD, when moth flight and 75% complete and terminal growth on lodgepole pine was 40% complete. Larvae began leaving terminals for winter hibernation in early July at 600 DD, when terminal growth was 99% complete; the last larvae left in mid-August at 940 DD.