Black insect eggs on leaves may be from aphids, squash bugs, lace bugs or a variety of shield bug. Insects lay eggs as small as .04 inch, which are not easily seen by the naked eye. Some insects lay eggs in clusters or rows, and some are striped or held in plastic-like cups. Less than 1 percent of common garden insects are harmful, according to Cornell University service.
Some species of stink bugs lay black eggs with a fringe around the top, while others lay reddish-colored eggs in groups of 20 to 30. Stink bugs, also known as shield bugs, are beneficial insects that feed on moths, beetles, sawflies and weevil species that damage agricultural and ornamental plants. They have four wings and a large, triangular, green or brown plate on their back. Brightly colored marks on the shields distinguish some species.
Lace bugs lay small groups of black eggs in the spring. Adult lace bugs are 1/8 to ¼ inch long with light-colored bodies and ornate, lacy wings. The newly hatched nymphs feed for three weeks before maturing into winged adults. Lace bug host plants include hawthorn, chokeberry, walnut trees and chokeberry shrubs. They feed on leaves but do not cause extensive damage. Natural enemies include lady beetles and green lacewings.
Squash bugs are often misidentified as stink bugs because both emit an odor as a defense mechanism. The adult squash bug is 5/8 inch long with orange-and-brown stripes on the edge of its gray or black body. It feeds on pumpkin or squash foliage with its piercing mouthparts. Damaged leaves wilt, dry out and fall off. Its dark reddish-brown eggs often appear black and are laid in a v-shape formation on the underside of leaves. The eggs darken, as they get closer to hatching.
Aphids are soft-bodied insects with sucking and chewing mouthparts. Large infestations cause extensive damage to new, spring plant growth. Beneficial insects, such as ladybugs, hoverflies, lacewings and parasitic wasps, control aphid populations. Harmful aphid infestation produces black deposits of sticky liquid that resembles insect eggs. The sugary honeydew drops attract sooty mold that accumulates and turns leaves black. Ants feed on the egg-like drops of sooty mold.
- Cornell University; Companion Planting; Robert Beyfuss, et al.; Winter 1994
- University of Arizona: Stink Bug/Shield Bug
- University of Minnesota Extension; Lace Bugs on Deciduous Trees & Shrubs; John F. Kyhl, et al.; October 2002
- Backyard Nature: Insect Eggs
- University of Minnesota; Squash Bug; A. Genetzy, et al.
- University of Kentucky; Entomology; Aphids; Lee Townsend
- North Dakota State University; Integrated Pest Management; What is IPM?