Throughout most of south-central and interior on the largest leaf veins of Silver Birch (Betula CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, Alaska, birch (Betula spp.) trees are commonly pendula Roth), thereby tapping the maximum and fish or other wildlife—if they are not handled encountered in the forest and are one of the flow of phloem sap in a leaf (Hajek and Dahlston or applied properly. Use all pesticides selectively most widely used ornamentals in residential 1986). In spring adults feed on new leaves and and carefully. Since approved uses of a pesticide Birch Aphid areas. Alaskan homeowners have encountered in the fall on senescent leaves. Aphid feeding may change frequently, it is important to check greenish aphids (Euceraphis betulae (Koch.)) in causes a loss in plant vigor and, at times, tree the label for current approved and legal use. the summer on birch (Figure 1). death. Associated with high aphid populations Follow recommended practices for the disposal is honeydew, a sticky substance excreted by of surplus pesticides and pesticide containers. the aphids. Honeydew is nothing more than Mention of a pesticide in this publication does excess plant juices, mostly water and sugars not constitute a recommendation for use by that the aphids secrete. This sticky material the USDA, nor does it imply registration of a is quite attractive to ants and other insects, product under Federal Insecticide, Fungicide, and it forms a medium for the growth of a and Rodenticide Act, as amended. Mention of a proprietary product does not constitute an fungus known as sooty mold. Honeydew is not endorsement by the USDA. permanent and is easily washed away. Healthy, vigorous birch trees can usually sustain Birch Aphids two to three years of moderate to heavy By Edward H. Holsten, Research Entomologist, aphid feeding with only minor effects. The revised by Mark Schultz, Entomologist, USDA most common effects of heavy aphid feeding Forest Service, Alaska Region, State and Private are leaf discoloration and premature leaf Forestry. fall; temporary growth reduction; occasional Additional information on this insect can be Figure 1. Birch aphids and their castoff exoskeletons on a birch leaf branch dieback; and, sometimes, tree death. If obtained from your local UAF Cooperative (photo by Michael Rasy). a birch tree is not vigorous, its chances of death Extension Service office, Alaska State Forestry increase with two or more consecutive years of Associated with the aphids is sticky honeydew office, or from: heavy infestation. USDA Forest Service that rains down on cars, walkways, flowers, etc., and sooty mold that grows on the State & Private Forestry Life History Forest Health Protection honeydew and causes it to turn black. Birch aphids are dull green and about 1/8-inch 3301 “C” Street, Suite 202 Overall, aphid damage to Alaska birch forests is long (Figure 2). Aphids can be recognized by Anchorage, Alaska 99503 negligible. Trees in a yard or landscape situation their soft, pear-shaped body, long legs, and Phone: (907) 743-9455 are often damaged or weakened because of a pair of cornices (tubular structures) at the the stresses associated with the location and 2770 Sherwood Lane, Suite 2A posterior end of the abdomen. Cornicles Juneau, Alaska 99801-8545 condition of landscape trees. serveas wax-secreting tubes, and in some Phone: (907) 586-8883 aphid species, the body is virtually covered with 3700 Airport Way white, waxy fibers. Antennae are prominent Fairbanks, Alaska 99709 Damage United States Forest Service and threadlike. Wings, when present, are Phone: (907) 451-2799 R10-TP-98 Department of Alaska Region Revised Aphids are sap-sucking insects. Their delicate, membranous and greenish white and Agriculture www.fs.fed.us/r10/spf/fhp April 2011 mouthparts are developed for piercing plant are generally held roof-like over the body. phloem cells and sucking juices from which USDA is an equal opportunity provider and employer. they derive their nutrition. Birch aphids feed temperatures in forest settings. Increased from the area over the root zone. Such actions temperatures can cause a water stress in trees can cause water stress and/or soil oxygen and provide optimum conditions for aphid depletion to the tree. reproduction. Other stresses associated with Spring fertilization helps promote tree vigor. urban situations include soil compaction, root The UAF Cooperative Extension Service and trunk damage, water and nutrient stress, recommends that approximately 1 pound of and excessive soil over the root system. fertilizer per inch of tree diameter be applied by making a concentric series of holes 8 to Guidelines for Reducing Aphid Damage 10 inches deep around the tree starting 2 Aphid suppression is usually not warranted feet from the trunk and extending a few feet on forested lands; they are a natural feature beyond the drip-line of the tree. Any complete Figure 2. Winged birch aphid (photo by Jarmo Holopainen). Figure 3. Leaves damaged by birch aphid. in Alaskan forests and cause little permanent lawn or garden fertilizer high in phosphorus The life cycle of most aphids is unusual and damage to the host tree. Aphids would be a is adequate. Fertilization should begin in the label directions and absorbed by the leaves. complex. Most aphids overwinter in the great deal more destructive to trees and other spring and continue through the summer. Soil systemics are applied according to egg stage. The eggs hatch in spring into vegetation were it not for their numerous Stop fertilization before the tree goes into label directions, absorbed by the roots, and females that can reproduce without mating parasites and predators, such as small wasps, fall dormancy. This feeding program may not transported to the leaf tissue. When using (parthenogenetically) and give birth to living syrphid flies, two-spot ladybird beetle Adalia( be necessary every year. Fertilizer uptake, soil insecticides it is important to read and follow young. bipunctata (L.)), and birds. Climatic conditions type, rainfall, weather, and grass cover all will all label directions. will also limit insect numbers to a degree. In determine the frequency of reapplication. Several overlapping generations may be Contact the UAF Cooperative Extension urban areas where trees are grown in more produced quickly during the spring and A high velocity spray of water is effective in Service for recommended insecticides. isolated, artificial conditions, aphids can be summer, with only females being produced. dislodging aphids. It won’t get them all, but it more damaging to the trees health than in The first generation or two usually consists will reduce their numbers. A mild (2 percent) forest settings, and the homeowner may of wingless individuals, but eventually winged solution of dishwashing detergent in water or need to select one of the following control aphids appear. In the latter part of the season, insecticidal soap is effective in reducing low alternatives. a generation of winged males and females to moderate aphid populations. This solution will kill aphids on contact but has no residual appears. The individuals of this generation Low to Moderate Damage: mate, and the females lay eggs that overwinter. effect. If aphid feeding is low to moderate and birch Aphids are coldblooded and are very responsive trees are vigorous and showing little leaf Heavy Damage: to changes in temperature. During warm, dry discoloration, damage is minimal. The use of If birch shows signs of heavy aphid feeding summers, enormous aphid populations appear pesticides is usually not warranted, but the (leaf discoloration, leaf drop, etc.), chemical References in a relatively short time. The fact that aphids following steps should be taken: control may be warranted (Figure 3). Contact Hajek. Ann E. and Donald L. Dahlsten. 1986. can reproduce without mating produces this insecticides will kill aphids quickly but have Coexistence of three species of leaf-feeding population explosion. Care should be taken to avoid damaging the trunk, injuring the roots, altering the drainage a residual effect for only a week or so. Thus, aphids (Homoptera) on Betula pendula. Oecologia (Berlin) (1986) 68:380-386. Birch trees located in urban settings are, for patterns, or severely compacting the soil. more than one application in a season may the most part, less vigorous than their forest Make sure that trees receive adequate water be needed. Systemic insecticides are longer counterparts because microclimatic conditions throughout the growing season. Excess soil lasting but take longer to become effective. are different. For example, temperatures near should not be placed on top of or removed Foliar systemics are applied according to Cover photo: Leaf and tree damage by birch aphid by Ed a dwelling or a road are usually higher than Holsten..