The Larch The larch sawfly () two percent of the emerging adults are males, by Ed Holsten, Research Entomologist, USDA The Larch Sawfly (: ) was first and reproduction is usually accomplished with- Forest Service, Alaska Region, State and Private recorded in North America in 1880. It is out mating. Eggs are deposited in rows under Forestry. believed to be of European origin. It now occurs the bark of currently elongating shoots on the in all Canadian Provinces and all of the north- branches usually causing a characteristic curling Additional information on this can ern tier states plus Maryland, North Carolina, of the new shoots. Eggs hatch in about a week. be obtained from your local USDA Alaska and West Virginia. It was first recorded from The young larvae move to and feed in groups Cooperative Extension office, Alaska State Alaska in 1965. Outbreaks of the larch sawfly upon tufts of needles. Feeding is completed in Forestry office, or from: became apparent in Alaska in 1993 when about three weeks; mature larvae drop to the 12,000 acres of tamarack (eastern larch) defolia- ground, enter the litter layer, and spin papery, Forest Health Protection tion was observed in interior Alaska. By 1996, brown cocoons. Because of the long period of State and Private Forestry this outbreak encompassed more than 600,000 adult emergence, all life stages may be found at USDA Forest Service acres and still continues, although at a slower the same time in the summer. There is probably 2770 Sherwood Lane, Suite 2A pace. Tamarack mortality (Cover photo) has one generation per year in Alaska. Juneau, Alaska 99801-8545 been observed over extensive areas of the inte- Phone: (907) 586-8883 rior as a result of more than seven consecutive Description Forest Health Protection years of feeding. In 1999, the larch sawfly Translucent eggs are approximately 1/16 inch State and Private Forestry was recorded from the Mat-Su valley and long. Newly hatched larvae have brown heads USDA Forest Service the Anchorage Bowl feeding on ornamental and cream-colored bodies. Mature larvae have 3301 “C” Street, Suite 522 Siberian larch. This is the first time that this shiny black heads with bodies that are gray Anchorage, Alaska 99503 defoliator has been recorded south of the Alaska green along the back and whitish beneath and Phone: (907) 743-9455 Range and no doubt represents an accidental introduction. By 2001, larch were are about 1/2 inch long (Figure 1). The papery or: observed feeding on Siberian larch on the Kenai brownish cocoons are capsule shaped and mea- sure about 7/16 by 3/16 inch. Adult females are www.fs.fed.us/r10/spf/fhp/fhpr10.htm Peninsula. The purpose of this brochure is to describe the life history and life stages of the The U.S. Department of Agriculture (USDA) prohibits larch sawfly and to present the homeowner discrimination in all its programs and activities on the basis with some guidelines for minimizing damage to of race, color, national origin, sex, religion, age, disability, ornamental and native larch. political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means Life History for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET In Alaska, winter is spent in the prepupal stage Center at (202) 720-2600 (voice and TDD). (brownish cocoons) in the litter layer on the forest To file a complaint of discrimination, write USDA, floor. Pupation occurs in the spring and the Director, Office of Civil Rights, Room 326-W, Whitten adults emerge from May through July depend- Building, 1400 Independence Avenue, SW, Washington, United States Prepared by Leaflet ing upon temperature and location. Less than DC 20250-9410, or call (202) 720-5964 (voice and TDD). Department of Forest Service R10-TP-101 USDA is an equal opportunity provider and employer. Agriculture Alaska Region September 2001 Figure 1. Mature sawfly larva. about 3/8 inch long with black antennae and  Many commercial insecticides are available and Photography Credits: bodies. The abdomen has a broad orange band effective against sawflies and can be used for Figure 1: Forest Pests of North America, IPM Photo CD short-term control, but may require additional and tapers sharply towards the rear (Figure 2). Series, The University of Georgia Cooperative Extension applications during the season. Check with your Males have yellowish antennae, an orange Service, Tifton, GA. local Cooperative Extension Service office for abdominal band, but the abdomen is cylindrical Cover photo: Field Guide to Forest Damage in British insecticides that are currently registered for con- and rounded at the rear. Columbia, March 1999. Joint Publication No. 17, BC trol of larch sawflies. Ministry of Forests and Canadian Forest Service. Damage Caused  Systemic insecticides are longer lasting, but take Figure 2: that feed on Trees and Shrubs. 1988. longer to become effective and require extreme Johnson, W.T. and H.H. Lyon. Cornell University Press, Heavily defoliated trees commonly refoliate caution in their application. These systemics can Ithaca, NY. after a few weeks. Repeated defoliation, how- be applied either to the foliage or to the soil to ever, can result in trees with thinned foliage, be absorbed through the roots and transported branch mortality, and a significant growth loss. Figure 2. Female sawfly. later to the foliage. Again, check with your local Larch growing on poor sites that have been Cooperative Extension Service office for insecti- cides that are currently registered. defoliated for consecutive years may die. Extension Service should be consulted for spe- cific information on the type and amount of Contact the Alaska Cooperative Extension Guidelines for Reducing Damage fertilizer to be applied. Service for recommended insecticides. For natural growing tamarack, there are few Normally, harsh winter weather with below control options. Native tamarack and ornamen- normal snowfall and parasitism of the overwin- CAUTION: Pesticides can be injurious to humans, tal Siberian larch growing in plantations and tering stage are the most important natural con- domestic , desirable plants, and fish or other other artificial settings such as urban areas are trol for larch sawflies. Insectivorous birds also wildlife—if they are not handled or applied properly. very susceptible to larch sawfly damage. It is Use all pesticides selectively and carefully. Since consume sawfly larvae during the summer. approved uses of a pesticide may change frequently, important to insure that trees in those situations it is important to check the label for current approved have the best possible growing conditions. Care Alternatives: When sawflies are sighted, several and legal use. Follow recommended practices for the should be taken to avoid injuring the roots, alternatives are available for their control: disposal of surplus pesticides and pesticide containers. either mechanically or through soil compaction. Mention of a pesticide in this publication does not  When sawfly populations are low, some defolia- constitute a recommendation for use by the USDA, Soil should neither be placed on top of nor tion may occur but most trees will refoliate later nor does it imply registration of a product under removed from the area beneath the crown of the in the growing season. The raking and disposal Federal Insecticide, Fungicide, and Rodenticide Act, as tree. In order to avoid moisture stress, adequate of needles and litter beneath the infested tree in amended. Mention of a proprietary product does not water should be provided to the trees through- the fall will remove the overwintering stage and constitute an endorsement by the USDA. out the growing season. Spring fertilization minimize sawfly defoliation the following year. also helps to promote tree vigor and to mini-  A high-pressure water spray will dislodge many mize the effect that defoliators such as sawflies larvae from the needles, but will need to be might have on a tree. The USDA Cooperative repeated fairly frequently during the season. Handpicking of the larvae from small trees is also effective.