Regional Pest Watch: Northeast
Regional Expert: Dr. Ana Legrand, PhD, Entomologist, University of Connecticut
Snow-covered winters and warm, humid summers create ideal growing conditions for plants—and garden pests. Our regional expert shares how to identify three common pests and the damage they can cause in your garden.
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Four-lined plant bug (Poecilocapsus lineatus)
This 1/3-inch-long green-yellow plant bug has four black stripes and is most active in late spring to early summer. The nymphs are bright red to orange with black spots on the abdomen.
Favorite plant
The four-lined plant bug is a pest of more than 250 plant species but seems especially fond of plants in the mint family.
Damage to look for
Both adults and nymphs use piercing mouthparts to feed on foliage. This causes black or brown spots that are often confused with fungal disease. In small numbers, four-lined plant bug feeding only makes the plants look bad. But with a big population, entire leaves can curl up and fall off. New growth may be deformed.
Integrated Pest Management (IPM) tips
Insecticidal soap can get rid of nymphs. Handpick the larger adults. Dr. Legrand recommends holding a container of soapy water under infested foliage and tapping the plant so these fast-moving insects fall in and drown. Look closely at leaf stems for 2- to 3-inch-long scarring where females have made small slits to lay eggs. Remove these leaves and put them in the trash to prevent the next generation from developing.
Bagworm (Thyridopteryx ephemeraeformis)
You’re more likely to see the “bags,” or cases, than the gray caterpillars with dark splotches inside them. The bags start small and get larger as the caterpillar grows and adds more foliage pieces. Bagworms are active in spring through summer, producing one generation per year.
Favorite plants
Bagworms are attracted to a wide range of conifers, including arborvitae (Thuja occidentalis), juniper (Juniperus spp. and hybrids) and spruce (Picea abies). They’ll also feed on deciduous trees, such as sycamore (Platanus occidentalis), honey locust (Gleditsia triacanthos f. inermis) and linden (Tilia spp.).
Damage to look for
Bagworm larvae eat the needles and foliage of their host tree. Though the damage is light at first, as the larvae grow they cause serious defoliation, which can be especially hard on evergreens.
IPM tips
Keep an eye out for the distinctive bags the larvae create from silk and bits of foliage from the host plant. Pull or cut them off and send them away in the trash. For larger trees or infestations, spray Bt when young bagworms emerge in late spring to early summer.
Rising pest to look out for in the Northeast:
Allium leaf miner (Phytomyza gymnostoma)
The small gray 1/8-inch-long flies have a yellow head and produce two generations of cream 5/16-inch-long larvae each year. They’re most active in spring and fall.
Favorite plant
Ornamental allium (Allium spp. and hybrids), chives, garlic and leeks are beginning to be attacked by this new invasive pest in Northeast gardens.
Damage to look for
In spring and fall, females lay eggs on the tips of allium leaves. The spring larvae tunnel through the leaves and leaf sheaths, causing disfigured foliage and creating openings for fungi and bacteria. In fall the larvae overwinter.
IPM tips
Insect netting or row cover can help prevent adults from laying eggs in spring. Keep an eye out for rows of white spots (the injury caused by egg laying) descending from leaf tips near the ends of the leaves, and remove any that you find. Rotate crops and clean up the garden in fall so larvae don’t have a place to overwinter.
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