Willow leafblotch miner Micurapteryx S. interior Willow salicifoliella Jim Kruse, Forest Entomologist, and Nicholas ( and sandbar willows ( ) have all Lisuzzo, Biological Science Technician,USDA Forest Service, Alaska Region, State and Private Leafblotch Miner (Chambers)) been identified as species actively attacked Forestry.Additional information on this insect can be obtained from by the leaf miner. Populations of the your local Alaska Cooperative Extension office, Alaska State Willow leafblotch miner is a moth leaf miner fluctuate in a rough cycle that Forestry office, or from: (Lepidoptera: Gracillariidae) native to develops into an outbreak approximately Forest Health Protection North America that has been observed every ten years. Population levels are State and Private Forestry within its natural range throughout controlled by localized weather patterns USDA Forest Service interior Alaska. The largest recorded l 11305 Glacier Highway and populations of natural predators. Juneau, Alaska 99801-8626 outbreaks have occurred predominately Individual eggs are laid on the underside of Phone: (907) 586-8883 in the upper Yukon RiverSalix Flats. The larvae the eaves in early summer, and the larvae, feed upon the inner tissue of the leaves when hatched, feed upon the upper surface Forest Health Protection of various willows ( spp.). Although State and Private Forestry and move inside the leaves. Mature larvae USDA Forest Service outbreaks of willow leaf miner have been exit the leaves through narrow slits made 3301 “C” Street, Suite 202 recorded multiple times over the last few in the lower surface, and spin silken Anchorage, Alaska 99503 decades, relatively little is known about coverings on the leaf surface or on the Phone: (907) 743-9449 what controls their population levels, or to ground prior to pupating. The adult moths Forest Health Protection what extent the insects cause permanent emerge in August and overwinter, laying State and Private Forestry damage.Description their eggs the following spring at bud USDA Forest Service break. 3700 Airport Way Fairbanks, Alaska 99709 Phone: (907) 374-3758 Willows that have dense hairs on the Mature larvae are 4-7mm long and pale underside of the leaves, such as felt http://www.fs.fed.us/r10/spf/fhp yellow in color. Adults are small gray moths with mottled areas of light and dark The U.S. Department of Agriculture (USDA) prohibits gray to brownish gray on the forewings. discrimination in all its programs and activities on the basis Their wingspan is 10-11mm and their of race, color, national origin, sex, religion, age, disability, antennae are approximately as long political beliefs, sexual orientation, or marital or family as their wings. The eggs of the willow status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means leafblotch miner are pale green, and for communication of program information (Braille, large 0.5mm in diameter. They are laid solitary print, audiotape, etc.) should contact USDA’s TARGET onLife the History underside of willow leaves. Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Figure 1. Building, 1400 Independence Avenue, SW, Washington, United States Prepared by Leaflet Willow leafblotch miner is known to affect DC 20250-9410, or call (202) 720-5964 (voice and TDD). Department of Forest Service R10-TP-150 Salix arbusculoides S. barclayi USDA is an equal opportunity provider and employer. Agriculture Alaska Region May, 2010 at least ten of the 37 species of willows An example of “leaf blotch” mines S. bebbiana S. glauca caused by the larvae of the willow leafblotch found in Alaska. In particular little-tree miner. Areas where larvae have been feeding ( ), Barclay ( ), typically turn red or brown. Bebb ( ), grey leaf ( ), S. alaxensis Alternative 3: leaf willow ( ), appear to be When planting consider protected by preventing egg attachment using those species of willows not targeted to the underside of the leaves. Species of by the leafblotch miner or consider willow with variable amounts of hair on replacing current susceptible willows with the bottom of their leaves appear to be non-susceptible species. protected in proportion to their amount of CAUTION: hairs.Damage Figure 2. Pesticides can be injurious to humans, domestic animals, desirable An adult specimen of the willow leaf- Figure 3. plants, and fish or other wildlife—if they The leaf miners create areas of necrotic blotch miner. The image depicted is roughly ten are not handled or applied properly. Use all times larger then the actual size of a typical moth of pesticides selectively and carefully. Since blotches (i.e. dead and discolored tissue) this species.. Several species of willow side-by-side on the upper surfaces of the willow leaves. along the Dalton Highway, AK. The damaged approved uses of a pesticide may change Damage can become severe enough to kill already exist which act to control population foliage is visible in susceptible species of willow. frequently, it is important to check the label the leaf or the entire branch, and feeding for current approved and legal use. Follow outbreaks (e.g. predators , parasitoids , and tree vigor. Any complete lawn or garden recommended practices for the disposal of can result in the complete defoliation of the weather cycles). fertilizer high in phosphorus is adequate. surplus pesticides and pesticideontainers. tree. Because willows are well-adapted to In urban areas where trees are grown in Fertilization should begin in the spring Mention of a pesticide in this publication disturbances they can often recover unless more isolated, artificial conditions the and continue through the summer. Stop does not constitute a recommendation defoliated for several consecutive years. Alternativehomeowner 1:may wish to select one of the fertilization before the tree goes into fall for use by the USDA, nor does it imply Mortality has been observed, but due following control alternatives: dormancy. This feeding program may not registration of a product under Federal to the limited economic value of willow Insecticide, Fungicide, and Rodenticide If leaf miner feeding is low be necessary every year. Fertilizer uptake, throughout North America, little research soil type, rainfall, weather, and grass Act, as amended. Mention of a proprietary has been conducted to quantify the impact to moderate and willows are vigorous and product does not constitute an endorsement showing little leaf discoloration, damage is Alternativecover all will 2: determine the frequency of by the USDA. of the willow leafblotch miner. In Alaska, reapplication. willows play an important ecologicalAlces role, minimal. The use of pesticides is usually not Photography Credits: providingalces a critical food source to several warranted, but the following steps should be If the willow shows signs of wildlife species, including moose ( taken: heavy damage (extensive leaf discoloration, Cover photo and Figure 1: Ken Zogas, USDA Forest Service ). The affect of willow leafblotch 1. Care should be taken to avoid leaf drop, etc.), Chemical control may be warranted. In the current year of defoliation, Figure 2: Courtesy of Microleps.org miner damage on the nutritional quality of damaging the trunk, injuring the roots, Figure 3: James Kruse, USDA Forest Service willows as wildlife forage is currently not altering the drainage patterns, or severely it is best to insure that the trees receive wellGuidelines understood. for Reducing Damage compacting the soil. Make sure that trees adequate moisture in order to re-flush receive adequate water throughout the leaves. There are foliar and systemic growing season. Excess soil should not be pesticides available for controlling leaf miner populations. When using pesticides Control methods on a landscape scale placed on top of or removed from the area it is important to read and follow all label are expensive, therefore, natural cycles over the root zone. Such actions can cause directions. Contact the University of are responsible for limiting population water stress and/or soil oxygen depletion to Alaska Cooperative Extension Service for growth. Since the willow leafblotch miner the tree. recommended insecticides and information is a native pest, there are mechanisms that 2. Spring fertilization helps promote on how to apply them.