Garden Column for Concord Independent/Tribune
Darrell Blackwelder
June 2, 2003

    Homeowners are complaining about a strange, white insect infesting their silver maples. These are wooly alder aphids found amassed on the underneath sides of the leaves.   These insects require silver maple or alder to complete their life cycle. These aphids cause little permanent damage to their host plants although their appearance often causes alarm. The insect is really a nuisance sucking plant juices and secreting much honeydew which causes dark sooty molds. This mold disfigures the surfaces beneath infested trees and can be a royal pain if sidewalks or cars are nearby. Aphids secret a sticky honeydew that attracts bees, wasps and flies to the sweet liquid. Infested leaves shrivel and eventually drop prematurely.
    Eggs of the woolly alder aphid over-winter in cracks and crevices on the bark of silver maple trees. Nymphs are now emerging to begin their feeding on the underside of new leaves. All the young are females which give birth to live young and produce large colonies. Their continuous feeding causes the leaves to curl and pucker.
Control of this pest is rarely an option because infested silver maple trees are so large that control measures are expensive or impractical. If this is a recurring problem, one should consider removal and planting shade trees other than silver maple.
    Those that want control on large trees will require the services of a commercial operator. Because of the heavy wax filaments covering the aphids' bodies and the "pockets" produced by the feeding of aphids on the leaves of maple, good coverage and penetration with heavy duty equipment is needed for adequate control. For best results, spray maple trees when the production of honeydew is first noted and repeat as needed. Homeowners can use malathion or insecticidal soap to control the pest on smaller trees.
   

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com , e-mail Darrell_Blackwelder@ncsu.edu or phone at 704-633-0571.