United States
Department of
Agriculture

Forest Service

Northeastern Area

NA-PR-06-98

Scarlet Oak Sawfly

Oak sawfly mature larvae
Oak sawfly mature larvae
Oak sawfly defoliated branch
Oak sawfly defoliated branch
Oak sawfly larvae —feeding activity
Oak sawfly larvae —feeding activity
     
The scarlet oak sawfly, Caliroa quercuscoccineae (Dyar) skeletonizes leaves of scarlet, black, pin, and white oaks in eastern North America. It is also called the oak slug sawfly because of the fact that the larvae are covered with a coat of slime that helps them adhere to foliage.
Trees defoliated by oak sawfly
Trees defoliated by oak sawfly
Larvae feed on the lower surface of the leaves, leaving only a fine network of veins which gives the leaf a transparent appearance. Defoliation starts in the upper crown in early summer and progresses downward. By late summer, heavily infested trees may be completely skeletonized.

Larvae overwinter in cocoons in the litter layer, and adults emerge in the spring. The adults, which resemble

Adult oak sawfly
Adult oak sawfly
small fly-like insects, are about 6-8 mm long and are black with light yellowish legs. Females lay eggs in rows in the lower leaf surface along the sides of the midribs and larger veins. Eggs hatch within 1-2 weeks, depending on the temperature. Several larvae feed on the same leaf. Full-grown larvae are slug-like, yellowish-green, and about 12 mm long. There may be two to three generations per year.

Microbial diseases and other natural enemies generally keep the sawfly in check. In outbreak years, insecticides may be needed on high-value trees.

Oak sawfly oviposition damage
Oak sawfly oviposition damage
Photographs by Sherri F. Hutchinson, WV Department of Agriculture  
   
For additional information, contact:
USDA Forest Service
180 Canfield Street
Morgantown, WV 26505
(304) 285-1541
  WV Department of Agriculture
Plant Industries Division
1900 Kanawha Boulevard, East
Charleston, WV 25305-0191
304-558-2212