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

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Phylloxera spp.

Importance -- Phylloxerids are very small, aphid-like insects that attack the foliage and buds of red and white oak trees of all sizes. Heavy infestations stunt and weaken the trees. The distorted foliage mars the beauty of ornamentals.

Identifying the Insect (figure 35a). -- Phylloxerids are small .01 to .02 inch (0.3 to 0.6 mm) long, aphid-like, lack cornicles and usually spiny in appearance. Winged forms have reduced wing veination. They are usually found in clusters.

Identifying the Injury (figure 35b). -- Buds and young developing leaves (undersurface) on terminals and branch ends are attacked, causing the leaves to curl and twist. Growth may be reduced or stopped. Mature and nearly mature leaves are unaffected. Damage occurs during spring and early summer.

Biology. -- The biology of this pest is not well known, but overwintering occurs as eggs in bark crevices. Eggs hatch during the spring. There appear to be several generations per year.

Control. -- Natural controls usually keep damage to a minimum. Ornamentals may require chemical control.

Figure 35a

Figure 35b


Figure 35. -- (a) Close-up of oak phylloxerid feeding along leaf midrib; (b) left, leaves curled and deformed by phylloxerids; right, healthy leaves.
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