June 13, 2019
A dramatic and possibly widespread outbreak of the oak shothole leafminer (Japanagromyza viridula synonym Agromyza viridula) and oak anthracnose (Apiognomonia errabunda) has occurred this season. To date, samples and observations of the outbreak have been made in western and eastern Massachusetts, coastal Rhode Island, southern New Hampshire, eastern New York and eastern Pennsylvania. The oak shothole leafminer is a small fly in the family Agromyzidae. Not much is known about this particular species, although very short-lived outbreaks of this insect on ornamental oaks have been recorded in New England in the past. The oak anthracnose pathogen appears to be readily colonizing foliage damaged by the leafminer. The anthracnose damage appears mostly minor to moderate in severity (leaf spots and blotches). However, for some trees the disease has been far more damaging (leaf wilting, death and premature shedding). Infected leaves may have tan to brown-colored spots and blotches or appear blackened and wilted.