Jeff Hahn, Asst. Extension Entomologist
There are several caterpillars that have been detected feeding on the leaves of blueberries recently. One species is the copper underwing, Amphipyra pyramidoides. This insect, also known as the pyramidal fruitworm, is bluish green with a thin yellow stripe running the length of its body along its sides and small whitish patches. It also possesses a conspicuous hump on the end of the abdomen and grows to about 1 ½ inches when fully grown. This caterpillar feeds on a wide variety of plants in addition to blueberry, such as trees (e.g. apple, basswood, maple, oak), shrubs (e.g. lilac, viburnum, and rose), and fruit including grape, raspberry, and currant.
You can also find forest tent caterpillars, Malacosoma disstria, in your blueberries. Also referred to as armyworms, these caterpillars are easily identified by their blue and black bodies, the distinctive white footprint shaped spots on their back as well as hairs that stick out along the sides of their body. These caterpillars are about two inches long when fully grown. Despite their name, they do not make conspicuous webs in trees. They commonly feed on many deciduous trees, including aspen, birch, maple, crab apple, apple, ash, oak, and elm.
Another caterpillar feeding on blueberry leaves is the linden looper, Erannis tiliaria. This caterpillar, a type of inchworm, is brown down the top of the body, has a bright yellow stripe along its sides, 10 thin black stripes, and a grayish white underside. A linden looper is over an inch when fully grown. Besides blueberries, it is commonly found on hardwood trees and shrubs, including linden, rose, elm, maple, oak, ash, serviceberry, and cherry.
These caterpillars generally do not occur on large numbers on blueberry but they are capable of minor up to severe defoliation. If management is necessary, handpick and destroy small numbers of caterpillars. If an insecticide is desired, low impact products include Bacillus thuringiensis, insecticidal soap, and spinosad are effective. Other insecticides include permethrin. Be sure that blueberries are listed on the label of any product you wish use on them.