The Maine Forest Service is asking residents to be on the lookout this year for two insect infestations, both of which have been spotted in Gorham: the native spruce budworm (SBW) and the invasive emerald ash borer (EAB).

Spruce budworm is one of the most damaging forest insects in Maine and North America. While they are native in our forests, severe outbreaks occur every 30 to 60 years and can cause devastating damage to balsam fir and spruce trees while the insect is in its caterpillar stage.

The last big occurrence of SBW in the 1970s damaged or killed close to 7 million acres of trees. Recent severe defoliation is occurring in southern Quebec and is expected to move south towards Maine over the next three years. Large-scale damage of this proportion not only kills trees but also impacts air quality and can become a fire hazard as well.

In southern Maine, the State is asking owners of woodlots, Christmas tree farms and homeowners with landscaping specimens to be on the lookout for signs of infestation. If possible, take a close-up photo of the pest and the damage that is occurring and contact the Maine Forest Service at forestinfo@maine.gov. Look for the tab for reporting insect infestation or call (207) 287-2791.

Here’s how to identify SBW on fir or spruce trees. Spruce budworm caterpillars feed on the outer portions of the tree on new growth, the tips that develop in the current year. Homeowners can place a white sheet of paper beneath a branch and shake the branch sharply to see if any larvae will fall onto the surface. Be on the lookout for gray weblike fibers on the tips of branches.

Small SBW outbreaks can be treated with insecticides. Look for products registered for caterpillar control with the active ingredient Btk (Bacillus thuringiensis kurstaki). Want to steer clear of pesticide use? If the infestation is light and the trees are small, you can hand prune the tips of branches once a week or so. But you have to be vigilant over the course of the summer and next year as well. Put the clippings in an airtight bag, not into compost.

Natural predators, birds such as the black-capped chickadee, red-breasted nuthatch, and pine siskin and some wasps will feed on them and help keep the caterpillars in check if their population numbers are low. Mature larvae will drop to the ground and pupate in the soil around host plants with typically two or more generations per year.

The second pest to watch for, the emerald ash borer, has been found in all of Cumberland County. First spotted in 2018, this brilliant green insect threatens all of Maine’s ash species except for mountain ash. In order to slow the spread of this invasive species, firewood from outside the state should be banned. To identify, look for highly active woodpecker activity on infested trees, which will have a flecked outer marking on the bark called “blonding,” S-shaped serpentine patterns under the bark, or D-shaped exit holes.

Also, do not be fooled. The EAB has a doppelganger, a twin called the tiger beetle. Both are a brilliant iridescent green. The tiger beetle is a beneficial native, so do not kill it or report it. The tiger has big eyes, longer antennae and legs and a cinched-in waist. It will be found on the ground, not on trees like the EAB. Several photo apps such as Seek by iNaturalist can help you identify both of these problematic Maine pests, as well as many other insects just for fun.