Woolly alder aphids, Paraprociphilus tessellatus, are noticed primarily in the spring on the undersides of silver maple leaves. They are called WOOLLY alder aphids because of the white fluff the aphids secrete to cover their bodies. Woolly alder aphids are also called maple blight aphids. Winged woolly alder aphids are black to gray with a 3/8 inch wingspan. The abdomen is covered with white, fluffy secretion. Plump, gray, wingless aphids on maple leaves are about 1/16 inch long and are concealed beneath dense, white, waxy strands. On alder, wingless aphids have short, dense strands that are divided into small squares. Each egg is covered with a white woolly coat. Nymphs resemble wingless adults but are somewhat smaller. This aphid sucks sap from the leaves and excretes honeydew, a sweet, sticky liquid that covers lawn furniture, walks, and the ground cover under the trees. Dark sooty mold fungi grow in the honeydew and further disfigure objects in the landscape. Bees, wasps and flies are attracted to the honeydew so that the landscape becomes a sticky, dark, insect zoo.
Woolly alder aphids require both alder and silver maple to complete their life cycle (Woolly alder aphid on red maple has been reported rarely.). Eggs of the woolly alder aphid overwinter in cracks and crevices on the bark of silver maple trees. In spring, nymphs emerge and begin feeding at the midvein on the underside of new leaves. All the young are females which give birth to live young and produce large colonies. Their feeding on the foliage causes the leaves to curl and pucker. In late spring and early summer the last generation of woolly alder aphids develops wings and migrates to alder (hence the name woolly ALDER aphid). Summer is spent feeding on the stems of alder. The migrating generation of woolly aphids is conspicuous because their fluffy, white wax shows up brightly as the aphids seem to float aimlessly along. On alder, the whole group of aphids in all stages of development may become enveloped in a white, fluffy secretion that may completely obscure the whole colony. In autumn the aphids migrate back to maple to lay eggs in cracks and crevices on the bark for next year's generations. Each egg is covered with a white woolly coat. The last alder generation develops into males and female that fall fly to silver maple trees and mate. This fall generation of woolly aphids migrating from alder is not nearly as conspicuous as the summer generation, and most folks don't even notice the aphids on the bark. Each mated female lays only one egg, the overwintering stage. Some aphids also overwinter in colonies on alder where they reproduce by giving birth to live young females only.
Although their presence usually causes alarm and is a real nuisance, these aphids apparently cause little permanent damage to their host plants. Control of this pest on alder is rarely employed because alder is not used as a landscape plant, and predators, such as lacewings and lady beetles, may keep this pest below damaging levels. Infested silver maple trees may become so large that control measures are expensive. In areas where alders are growing wild and cannot be eliminated, consider planting trees other than silver maple.
Insect control on shade trees is frequently not practical because of high treatment cost and limited damage by the pests. Often large trees are infested and satisfactory treatment requires the services of a commercial operator. Because of the heavy wax filaments covering the bodies of the aphids and the "pockets" produced by the feeding of aphids on the leaves of maple, good coverage and penetration are needed for adequate control. For best results, spray maple trees when the production of honeydew is first noted and repeat as needed to about June 15. For good control, use two applications at weekly intervals. Following are some insecticides labeled for aphid control. See North Carolina Agricultural Chemicals Manual for additional choices.
|bifenthrin||(Talstar)||10% wettable powder|
|imidacloprid||(Merit) & other||follow label instructions|
|*insecticidal soap||various||follow label instructions|
|fluvalinate||(Mavrik)||23% aquaeous flowable|
|* Suitable for home use.|
- Woolly Alder Aphid. Anonymous. 2016 (update). Iowa State University Plant and Insect Diagnostic Clinic. Clinic Information.
- Woolly Alder Aphid, Paraprociphilus tessellatus (Fitch). Hanson, T. and E. B. Walker. No Date. Field guide to common insect pests of urban trees in the Northeast. Waterbury, VT: Department of Forests, Parks and Recreation.
- Woolly Alder Aphid (Family Aphididae). Redmond, K. 2014. University of Wisconsin UWMilwaukee Field Station.
- Extension Plant Pathology Publications and Factsheets
- Horticultural Science Publications
- North Carolina Agricultural Chemicals Manual
For assistance with a specific problem, contact your local Cooperative Extension center.
Publication date: May 20, 2001
Revised: Oct. 22, 2019
Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your local N.C. Cooperative Extension county center.
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