Better Yields Through Science

Shade Tree Diseases & Pests

DiseaseSymptoms, Life-cycle and pest management
Maple GallScientific Name: Eriophyidae

Maple, Acer spp., leaves are often infested with a wide variety of brilliantly colored, odd-shaped galls and blotches. Some of these abnormal plant cell growths called galls are caused by very small eriophyid mites in the family Eriophyidae. Members of this family of mites are commonly referred to as eriophyid mites. Several species of eriophyid mites cause leaf galls on maple. They are the maple bladdergall mite, Vasates quadripedes Shimer, maple spindle gall mite, V. aceriscrumena (Riley), and some erineum gall mites, Eriophyes spp.

The best time to treat an infested tree is delayed dormant before buds swell. Adults move from their overwintering sites to new growth at this time of the year. This treatment may help reduce the eriophyid mite population on an infested tree.
Nectria Canker Pathogen: Nectria cinnabarina

The fungus invades wood damaged by freezing, hail, animals and insects. Most hardwoods with such injuries are susceptible to attack. Slightly sunken areas (cankers) develop around wound or damaged tissue. Both the asexually formed spores (conidia formed all year) and the sexual spores (ascospores) formed in the late summer are capable of causing disease.