Aroostook County potato growers have been urged by University of Maine Cooperative Extension crop scientists to intensify monitoring for late blight, as recent weather conditions have become ideal for the disease. High temperatures and humidity followed by rainfall create a conducive environment for Phytophthora infestans spores to infect potato plants.

Although no active infections have yet been reported in Maine, spores were detected across Aroostook County last week, prompting an urgent advisory.

“While this is not out of the ordinary, [the spores’] early presence is a concern given the long season ahead,” extension scientists stated. “All growers who have not begun a fungicide spray regimen should do so and stay on a five-day spray schedule for the time being.”

The advisory, part of the weekly Potato Pest Alert, is prepared by a team including Sean McAuley, James Dill, Alicyn Smart and Griffin Dill.

Late blight is a fungal‑like disease that causes water-soaked lesions on leaves and tubers and can devastate crops if left untreated. Spores are airborne and cannot survive in soil, making timely fungicide applications critical.

Caleb Goossen of the Maine Organic Farmers and Gardeners Association, writing in the June 27 Pest Alert, added that extreme heat can also lead to sunburn on plants:

“To protect against sunburn, plants should have an adequate supply of water, and full plant canopies should be encouraged,” he said. “As of now, we don’t have reason to think there are active infections on plants in the state, but this early spore detection is perhaps a beneficial shock to the system, reminding folks to keep on the lookout for disease symptoms.”

Insect pests also vary regionally: Colorado potato beetles are active in northern and central Aroostook County, aphids are appearing in southern Aroostook and central Maine, while potato leafhopper levels remain low.