Spruce and Giant Conifer Aphids
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Spruce and Giant Conifer Aphids The purpose of this brochure is to describe by Mark Schultz and Ed Holsten, Entomologists, Spruce and Giant the life history of the spruce and giant conifer USDA Forest Service, Alaska Region, State and aphids and to present the homeowner with Private Forestry. Special thanks to Liz Quadra, some guidelines for minimizing damage from Cooperative Extension, State of Alaska, for her Conifer Aphids these insects to ornamental spruce. helpful review. Spruce Aphid Additional information on this insect can be obtained from your local USDA Cooperative Sitka spruce is periodically subjected to attack Extension Service office, Alaska Division of by the spruce aphid, which can produce severe needle drop and death of the tree. Spruce aphid Forestry office, or from: Figure 2. Yellow patches on needles are the first sign outbreaks are usually preceded by mild winters, Forest Health Protection of aphid feeding. Discoloration is more intense in spring and normally last for a short time, perhaps two and early summer. State and Private Forestry or three years. USDA Forest Service 2770 Sherwood Lane, Suite 2A infest new spruce. By midsummer the popu- Juneau, Alaska 99801-8545 Life History lations may reach a low point. This decline Phone: (907) 586-8811 Spruce aphids are small green insects about 1 in aphid numbers during the late summer is to 2 mm long (Cover photo) and overwinter as due to numerous factors including migration by Forest Health Protection wingless females. These females produce live winged individuals, increased parasitism, and State and Private Forestry young that grow to maturity within three weeks changes in the chemistry of the spruce needles. USDA Forest Service and then begin producing their own progeny. In the fall, the aphids may increase in number 3301 “C” Street, Suite 522 Since spruce aphids can reproduce throughout and infest the shoots that were produced earlier Anchorage, Alaska 99503 the year, large colonies may develop during in the year. This second peak in September and Phone: (907) 743-9455 mild winters. Aphid damage may become October is usually not as damaging as the spring or: apparent in March or April before the new population, but significant defoliation may still spruce growth begins. Populations continue to occur if the autumn is a mild one. http://www.fs.fed.us/r10/spf/fhp/fhpr10.htm increase until early summer, when many of the The U.S. Department of Agriculture (USDA) prohibits aphids develop wings (Figure 1) and fly off to Damage discrimination in all its programs and activities on the basis Aphids derive their nutrition from plants by of race, color, national origin, sex, religion, age, disability, Figure 1. Adult winged political beliefs, sexual orientation, or marital or family piercing the tissues and sucking the juices from spruce aphid that is feed- status. (Not all prohibited bases apply to all programs.) the needles. The spruce aphid prefers older nee- Persons with disabilities who require alternative means ing. for communication of program information (Braille, large dles and does not attack the new growth until late print, audiotape, etc.) should contact USDA’s TARGET summer when the newest foliage hardens and Center at (202) 720-2600 (voice and TDD). begins to resemble the older needles. Spruce To file a complaint of discrimination, write USDA, aphids begin their infestations in shaded portions Director, Office of Civil Rights, Room 326-W, Whitten United States Prepared by Leaflet of the lower crown, rarely affecting the leader Building, 1400 Independence Avenue, SW, Washington, Department of Forest Service R10-TP-96 and upper crown except in epidemics. The first DC 20250-9410, or call (202) 720-5964 (voice and TDD). Agriculture Alaska Region August 2001 USDA is an equal opportunity provider and employer. signs of feeding are yellow patches on the needles in the late winter or early spring (February–March). neither be placed on top of nor removed from Alternatives: When aphids are sighted, several The needle discoloration intensifies in the spring the area beneath the crown of the tree. In order alternatives are available for their control: and early summer (Figure 2) and is sometimes to avoid moisture stress, adequate water should A high-pressure water spray will dislodge many accompanied by a black fungal growth that be provided to the trees throughout the growing of the aphids and knock them to the ground, but looks like soot. The affected needles will later season. Spring fertilization also helps to promote this will need to be repeated frequently during turn brown and drop prematurely (Figure 3), tree vigor and to minimize the effect that defolia- the season. leaving only the tips of the new growth unaf- tors such as aphids might have on a tree. The fected. This feeding reduces the vigor of the tree, Alaska Cooperative Extension Service should be A spray of 2 percent solution of mild dishwash- ing detergent or insecticidal soap in water is causes growth loss, and if severe, may kill the consulted for specific information on the type fairly effective when aphid populations are low. tree. Aphid feeding is usually limited to spruce and amount of fertilizer to be applied. growing along beach fringes or near the water Many commercial insecticides are available and Figure 4. Defoliated Stika spruce on Mayflower Island, Normally, harsh winter weather is the most (Figure 4), although on occasion trees inland very effective against needle aphids. Douglas, Alaska. Attacked in 2000 and photographed important natural control for spruce aphids. In will be attacked and defoliated. in 2001. years when the winter is mild, homeowners For tree taller than 25 feet some chemical should expect aphid damage to occur, and must options are available and effective. A systemic Giant Conifer Aphid Damage recognize the importance of early detection of insecticide (one which will travel through the the insects. Aphids build up before the damage plant tissues) is best, and should be considered Adult giant conifer aphids are pear-shaped, 2 to Giant conifer aphids derive their nutrition also if the tree is being significantly attacked (i.e., live is noted, and in order to be effective, controls 5 mm long and brown colored. Adults (Figure 5) from sucking juices, but they feed on green aphids present and a considerable amount of the should be carried out before extensive defo- have long legs and winged adults will be present branches, not needles. Spruce aphids are much crown defoliated from prior year(s)). liation has occurred. This requires careful peri- in early to mid summer. These aphids feed on more numerous on trees than the giant conifer odic examination of the needles, beginning in When using any insecticide all label Instructions branches and stems, and are seldom seen on aphid. Trees that are only infested with giant February after a mild winter. Aphids will first should be followed very carefully. foliage. They are usually seen about the same conifer aphid are hard to pick out from unin- appear on shaded portions of the lower crown, time as spruce aphid. The female deposits eggs fested trees. Spruce aphids and giant conifer in mid-summer on foliage and branches. Eggs and can easily be controlled if apprehended at aphids tend to infest the same trees. Giant coni- CAUTION: Pesticides can be injurious to humans, this early stage. deposited late in the year overwinter and hatch fer aphid contributes to the decline of spruce domestic animals, desirable plants and fish, or other the next year. Trees that have large conifer aphid infested trees, but alone usually do not wildlife—if they are not handled or applied properly. aphids often have spruce aphids. Use all pesticides selectively and carefully. Since cause major damage. approved uses of a pesticide may change frequently, Figure 5. Giant coni- it is important to check the label for current approved Guidelines For Reducing Damage fer aphid adult. and legal use. Follow recommended practices for the Figure 3. Unaffected disposal of surplus pesticides and pesticide containers. Sitka spruce growing in plantations and other Mention of a pesticide in this publication does not new growth. constitute a recommendation for use by the USDA, artificial settings such as urban areas are the most nor does it imply registration of a product under susceptible to aphid damage. It is important to Federal Insecticide, Fungicide, and Rodenticide Act, as insure that trees in those situations have the best amended. Mention of a proprietary product does not possible growing conditions. Care should be constitute an endorsement by the USDA. taken to avoid injuring the roots, either mechan- ically or through soil compaction. Soil should .