How to Manage Pests
UC Pest Management Guidelines
Woolly Apple Aphid
Scientific name: Eriosoma lanigerum
(Reviewed 8/06, updated 1/11, pesticides updated 10/15)
In this Guideline:
DESCRIPTION OF THE PEST
Woolly apple aphids infest roots, trunks, limbs, shoots, and occasionally fruit of apple trees. The bodies of these bark-feeding aphids are completely covered by masses of white, wool-like, waxy materials. This aphid is found in colonies on the aerial portions of the tree and on roots during winter. The nymphs migrate up or down the trunk of infested trees during summer and fall.
The main injury to young and mature trees is stunting due to the formation of root galls. If populations are high, honeydew and sooty mold will also be problems, and aphids may enter the calyx end of fruit.
Woolly apple aphid is found throughout California's apple-growing regions, and it is a major pest in coastal counties. It occasionally infests pyracantha, hawthorn, and pear.
Winter Banana is one of the most susceptible varieties to aerial galls. Yellow Newtown fruit frequently has aphids in the calyx end. The Malling series of rootstock numbers 106 and 111 are resistant to this pest.
Aphelinus mali is a parasite that can completely control aerial colonies. In the absence of this parasite there can be large increases of aerial colonies and woolly aphids may be found in the calyx of the apple. Outbreaks of woolly apple aphid are most common following the use of pyrethroids, which destroys its natural enemies.
Organically Acceptable Methods
Resistant varieties and rootstocks as well as biological control are organically acceptable methods.
The delayed dormant application should control woolly apple aphids. A summer application (late July to August) will only be required if the parasites are disrupted. Foliage treatments may be necessary for young trees with severe infestations.
UC IPM Pest Management Guidelines: Apple
Insects and Mites
L. R. Wunderlich, UC Cooperative Extension, El Dorado County
Acknowledgment for contributions to Insects and Mites:H. L. Andris, UC Cooperative Extension, Fresno County
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
W. W. Coates, UC Cooperative Extension, San Benito County
C. Pickel, UC IPM Program, Sutter/Yuba counties