By Robert Cox, Colorado State University Cooperative Extension, Horticulture
If you find that the leaves on your plum tree are curled up, some very tightly, it is most likely caused by the Plum Leafcurl Aphid.
When you unroll one of the affected leaves, you'll probably notice many small, greenish aphids called plum leafcurl aphids. They are prevalent this spring on all kinds of plums, whether fruiting or ornamental. The aphids build up numbers quickly, as all are females that give live birth to already- pregnant females. As they feed on leaf liquids with a straw-like mouth, their saliva causes leaf cells to grow abnormally, forming the tight leaf curls you see. These leaf curls protect the aphids in a sense, as insecticides are difficult to apply to aphids inside the curls.
As ladybug populations build up, watch for their larvae, which look like small black and red alligators. They eat many aphids in a day. The newer leaves that develop after aphid populations decline (thanks to the ladybugs) will look normal. For more information on aphid control, see Aphid Control on Trees.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010