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Oak Pests - A Guide to Major Insects, Diseases, Air Pollution and Chemical Injury


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OAK LEAF APHIDS
Myzocallis spp.

Importance. -- These aphids infest the undersides of leaves, leaf stalks, and tender twigs of trees in the red and white oak groups throughout the East. Heavy infestations distort the foliage and weaken the plants. Honeydew and sooty molds further mar the beauty of ornamentals.

Identifying the Insect (figure 36). -- The aphids are .04 to .06 inch (1 to 1.5 mm) long, soft-bodied, pearshaped, with a pair of cornicles at posterior of abdomen. They may be yellow, green, pink, or brown, with darker pigmented blotches on the abdomen, and dusky bands on wings. Winged and wingless forms occur.

Identifying the Injury. -- Clusters of aphids feed largely on the underside of the leaves. Feeding injury curls and folds the leaves. Every leaf on a tree may be curled and distorted during heavy attacks. Leaf surfaces become sticky with honeydew followed by growth of black, sooty fungus.

Biology. -- Overwintering occurs as eggs deposited in bark crevices of host plants. The eggs hatch in the spring and nymphs begin feeding on the leaves. There are several generations per year, but the highest populations have been observed during the spring.

Control. -- Natural enemies usually keep infestations in check. Insecticides are sometimes needed on ornamentals and other high-value trees.

 

Figure 36

Figure 36. -- Oak leaf aphids.
 
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