While many children are hunting for candy eggs, gardeners may want to hunt for another kind: insect eggs.
“If you can spot those eggs and get rid of them before they hatch in spring, you’ll have fewer unwelcome insects to deal with during the growing season,” said Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle.
Insects are at their most vulnerable at the egg stage. “They can’t fly or wriggle away,” she said.
In many cases, you can prune out the part of a shrub or tree where you find an egg mass. In others, you may need to scrape an egg mass off tree bark and drop the eggs into a bucket of soapy water to kill them. “Be sure to wear gloves,” Yiesla said. “Contact with some kinds of eggs can irritate your skin.”
Before you destroy any insect eggs, be sure you have identified them correctly and that they are eggs of an insect that is genuinely harmful. Most insects are beneficial in the garden. For expert help in identifying eggs, consult the Plant Clinic (www.mortonarb.org/plant-clinic).
Never dispose of egg masses or egg-infested prunings in your compost. “Put them in the trash or into a landscape waste bag for collection to get them out of your garden,” she said.
Here are some types of eggs to look out for.
Spongy moth: This devastating pest of large shade trees, formerly called gypsy moth, lays masses of eggs in sheltered spots, including cracks in tree trunks, the undersides of branches, in firewood piles, and on lawn furniture, signs, birdhouses, and other protected surfaces around the yard. A tan egg mass is usually more or less oval and about 2 inches across. It feels soft to the touch, like felt, and spongy. Every egg mass you can spot and remove reduces the population of the caterpillars, which can eat every leaf on a tree. Wearing gloves, scrape the egg mass off with a putty knife, drop it into a bucket of soapy water, and let it sit for a couple of days to make sure the eggs are dead before disposing of them.
Viburnum leaf beetle: The larvae of these beetles can turn the leaves of a viburnum shrub to lace by eating all the tissue between the veins. The eggs are laid in tiny football-shaped bumps on the undersides of small twigs out toward the tip. Prune them out and check all other twigs on the shrub for more egg masses. Arrowwood viburnum (Viburnum dentatum) is the most vulnerable species, although all kinds of viburnum can be affected.
Eastern tent caterpillar: When these insects hatch — about the time the redbuds begin to bloom — the caterpillars gather in a nest they weave of silk at the fork of a branch. Prune those nests out promptly before the caterpillars emerge. Eastern tent caterpillars prefer trees in the rose family, such as wild black cherry, apple and crabapple, plum and peach, but will also feed on birch, willow, maple, oak and poplar.
Bagworm: These caterpillars infest deciduous trees and evergreens such as arborvitae and juniper. Their eggs overwinter in a nest in the form of a brown bag that looks like a collection of sticks dangling from a branch. The bags are 1½ to 2½ inches long. Pluck off any bags you spot and drown them in soapy water to keep the eggs from hatching.
Spotted lanternfly: This invasive pest, a newcomer to Illinois, feeds on tree of heaven, grapevines, hop vines, tulip tree and plum, cherry, apple, oak, walnut, willow and maple trees. Be on the lookout for suspicious egg masses and if you find one you suspect may be spotted lanternfly, take a picture and email it to lanternfly@illinois.edu to help scientists who are studying the spread of this pest. A spotted lanternfly egg mass will usually be on a smooth outdoor surface. When new, it has a gray, waxy, mudlike coating, but by spring the coating may be partly worn away so you can see the eggs. Each mass usually contains 30 to 50 small eggs. After you document your find, dispose of these egg masses as you would those of spongy moths by scraping them off into a bucket of soapy water to kill the eggs before disposing of them.
For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.
