Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001226
11/12/99
QUERCUS INSECT PROBLEMS
Galls (Vis. 2) cause homeowners much concern. There are
many types and the galls can be on the leaves or twigs.
Most galls are harmless so chemical controls are not
suggested.
Scales of several types are controlled with dormant sprays
applied in spring.
Aphids cause distorted growth and deposits of honeydew on
lower leaves. On large trees, predatory insects will
often bring the aphid infestation under control.
Boring insects are most likely to attack weakened or
stressed trees. Newly planted young trees may also be
attacked. Keep trees as healthy as possible with regular
fertilization and water during dry weather.
Caterpillars feed on oak. Large trees tolerate some
feeding injury without harm. Trees repeatedly attacked,
or having some other problem, may need spraying. Tent
caterpillars form nests in trees then eat the foliage.
The nests can be pruned out when small.
Twig pruner causes twigs to drop off in late summer.
The larvae ride the twig to the ground. Rake up and
destroyed fallen twigs.
Spider mite infested leaves first look dusty then
yellowed (Vis. 1).
Lace bugs suck juices from leaves causing them to look
dusty or whitish gray.
Leaf miners cause brown areas in leaves. To identify
leaf miner injury tear the leaf in two across the injury.
If the injury is due to leaf miner, upper and lower leaf
surfaces are separate and black insect excrement will be
seen.
Related information.
Pesticide Recommendations
Oak Galls
Lace Bugs
Spider Mites
Aphids on Ornamentals
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to commercial products or trade names does not imply
endorsement by MSU Extension or bias against those not
mentioned. This information becomes public property upon
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This file was generated from data base ZZ on 01/19/00.
Data base ZZ was last revised on 11/12/99.
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