Galls cause homeowners much concern. There are many types and 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 sprays of dormant oil applied in spring. Use Orthene applied 2 to 3 times at 7 to 10 intervals when the crawlers are first seen. Diazinon, Sevin or malathion are used whenever the crawlers are present.
Aphids cause distorted growth and deposits of honeydew on lower leaves. Spray small trees with Orthene, Diazinon, or malathion when aphids first appear. 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. No chemicals are available. 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. Chemical controls for tent caterpillar are Orthene, Diazinon, malathion, or methoxychlor.
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.
Lace bugs suck juices from leaves causing them to look dusty or whitish gray. Use sprays of Orthene, rotenone, or malathion when lace bugs are first noticed then again in 10 days. Spraying may be repeated in several weeks.
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. Use sprays of Orthene or Diazinon.
|Visual title - Visual size||Visual title - Visual size|
|Oak apple gall - 36K||Oak gall - 35K|
|Hedgehog gall on oak - 43K||Oak gall - 42K|
|Mites on oak - 41K||Variable oak leaf caterpillar damage - 45K|
|Variable oak leaf caterpillar - 29K|