. Cooperative economic insect report. Beneficial insects; Insect pests. - 817 - INSECTS NOT KNOWN TO OCCUR IN THE UNITED STATES PINE SAWFLY (Diprion pinl (L.)) Economic Importance: This dlprionid is of considerable economic Importance as a sporadic defoliator of pines in Europe. Outbreaks may become very severe and completely defoliate relatively large acreages of pines when conditions are favor- able. In September 1948, a severe outbreak in Scotch pine in eastern Spain defo- liated areas that measured up to 4^ by 1^-2 miles. In most areas, however, only a small percentage of pines defoliated
. Cooperative economic insect report. Beneficial insects; Insect pests. - 817 - INSECTS NOT KNOWN TO OCCUR IN THE UNITED STATES PINE SAWFLY (Diprion pinl (L.)) Economic Importance: This dlprionid is of considerable economic Importance as a sporadic defoliator of pines in Europe. Outbreaks may become very severe and completely defoliate relatively large acreages of pines when conditions are favor- able. In September 1948, a severe outbreak in Scotch pine in eastern Spain defo- liated areas that measured up to 4^ by 1^-2 miles. In most areas, however, only a small percentage of pines defoliated in one year are killed, but the trees may die if defoliated for 2 successive years. Damaged trees also seem very sus- ceptible to attack by several species of weevils. Damage appears to be most serious in trees on impoverished sites with sparse vegetation or in young trees from 4 to 8 years old. Needle damage will vary from 60 to 100 percent on the edges and in thin parts of the forest to 30 percent or less in the dense General Distribution of Diprion pini Distribution: Occurs throughout most of Europe, Algeria and through Siberia. Hosts: Attacks most pines, but apparently prefers Scotch pine. Will also attack spruce and fir. Life History and Habits: The biology is nearly the same for all species of the genus. In France, under normal conditions, adults emerge in April. Females deposit eggs in rows in pine needles in slits cut by the saw-like process of the female. Yoimg larvae begin to feed in May on the previous year's growth. Larvae start feeding on the needle near the tip and work downwards, eating about 5 mm. at a time. The attack continues Into June with pupation occurring on the branches. A second generation appears in July. The larvae feed to the end of the summer, then enter hibernation under cover or in the soil. Overwintering larvae do not pupate until 2 or 3 weeks before emergence in the spring. The larvae molt 5 or 6 times. They are often found in colonies,
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