DNR Question of the week
Q: I hear a lot about invasive insects like emerald ash borer and gypsy moths, but what are some of the good bugs that help keep our forests healthy?
A: There are many more beneficial insects than insect pests; we just don’t hear about them as often. One beneficial insect, the friendly fly, is named for its habit of repeatedly landing on people without biting. The larvae of this fly feed on forest tent caterpillars inside their cocoons. During the third or fourth year of a caterpillar outbreak in Minnesota, the friendly fly can kill nearly 90 percent of the cocoons.
Parasitic wasps also keep insect populations in check. Most parasitic wasps are extremely small, which is why we don’t usually see them at work. There are thousands of different species, none of which sting people, but nearly every insect species is attacked by parasitic wasps during at least one life stage. Beneficial wasps feed on pests such as spruce budworm, gypsy moth, fall webworm and emerald ash borer.
Many types of beetles, the largest and most diverse group of insects, are predacious and feed on aphids, scale insects, caterpillars, other beetles and more. The larvae of one beetle family called checkered beetles feed on harmful wood-boring insects such as bark beetles, potentially preventing an outbreak.
Val Cervenka, DNR forest health program coordinator