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Leaf stalk borer and petiole borer cause the same type of injury. Both insects bore into the leaf stalk just below the leaf blade. The leaf stalk shrivels, turns black, and the leaf blade falls off. The leaf drop may appear heavy but serious injury to a healthy tree is rare. Control measures are usually not needed.

Gall mites stimulate the formation of growths or galls on the leaves. The galls are small but can be so numerous that individual leaves curl up. The most common gall is bladder gall mite found on silver maple. The galls are round and at first green but later turn red, then black, then dry up. Galls of other shapes are seen less frequently on other types of maples. Galls are not serious, so chemical controls are not suggested.

Crimson erineum mite is usually found on silver maple and causes the formation of red fuzzy patches on the lower leaf surfaces. The problem is not serious so control measures are not suggested.

Aphids infest maples, usually norway maple, and may be numerous at times. High populations can cause leaf drop. Another sign of heavy aphid infestation is honey dew on lower leaves and objects beneath the tree. Aphids are controlled by spraying or they may be left alone. If not sprayed, predatory insects will bring the aphid population under control. Chemical controls include sprays of Diazinon and malathion.

Boxelder bug infests boxelders, primarily the female trees. The insect does no serious harm to the tree but is a nuisance when it overwinters in homes. The insects are red and black and can be vacuumed up when seen in the house. Control measures include removal of female boxelder trees. If boxelders are growing in adjacent yards removing your tree may not be effective.

Scales are an occasional problem on maples. Perhaps the most common is cottony maple scale. The insect forms a cottony mass on the lower sides of branches. Scales are controlled with dormant oil sprays applied in spring before growth begins. Scales may also be controlled with well timed sprays to kill the crawlers. Control crawlers with Orthene (note precautions on label about use on certain maples) or Sevin.

If borers become a problem it is an indication the tree is not growing well. Controlling borers involves keeping trees healthy. Chemical controls of existing infestations are more difficult. Proper control involves identification of the borer infesting the tree then applying insecticides at the proper time. Relatviely few chemicals are labeled for borer control in maple.

Visuals associated with this text.

Visual title - Visual size Visual title - Visual size
Cottony maple scale - 46K Boxelder bug - 20K
Cottony maple scale on maple - 53K Crimson erineum mites - 45K
Maple leafcutter damage - 22K Maple leafcutter damage close up - 18K
Occellate leaf gall - 10K Spindle gall mite on maple - 26K
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