Insects Are Off to an Early Start...

I find it amazing just how quickly the insects are coming to life throughout Missouri. Many of us hoped for colder winter temperatures that would knock insect numbers down, but that has not been the case. This was an ideal winter for most insects. When the temperatures dipped into the colder zones, snow provided a nice blanket under which the insects were well insulated.

The last couple of weeks have seen the rapid emergence of a native tree defoliator, the eastern tent caterpillar. Tent caterpillars build their tightly webbed tents in the crotch of various trees and shrubs, with their favorites being fruit trees such as wild cherry, plum, apple, and crabapple. They also feed on ornamental trees such as ash, birch, maple, oak, and poplar. These insects rest during the day within the tent and crawl out of the tent at night to chew on leaves and possibly on developing fruit. As each caterpillar leaves the nest, it will spin a strand of silk as it travels; it is assumed that this helps the caterpillar find its way back to the nest. Tent caterpillars over-winter in shiny brown egg masses glued to twigs, and eggs usually hatch at about the same time tree buds begin to break open. When abundant, tent caterpillars can destroy a substantial number of leaves and can weaken a tree. Tent caterpillars are usually kept under control by natural enemies which typically prevent tent caterpillar outbreaks from persisting long enough to cause serious damage. Tent caterpillar larvae and nests can easily be dislodged from trees and destroyed using a broom or heavy water spray. Once caterpillars are knocked off the tree or out of the nest, they usually cannot return to the tree and fall easy prey to ground feeding birds such as robins. If tent caterpillars are persistent from year to year, egg masses can be pruned out of the limbs in the fall. This activity reduces insect numbers the subsequent year.

The elevated temperatures this winter have also promoted an early emergence of aphids. This weekend, I water sprayed numerous plants throughout the yard to remove aphids. Aphids, sometimes called "plant lice," are among the most common insects that can attack home, garden, and landscape plants. They tend to cluster on the new growth of roses, perennials, and other plants. Aphids are soft-bodied insects and are usually 1/8 inch or less in size. They have long legs and antennae and are usually wingless. They come in a variety of colors including green, pink, yellow, tan, gray, white, or black. The aphids that I am currently seeing in high numbers in my yard are covered with a white powder-like coating, that, from a distance, appears to have a covering of mold or white spray paint. Aphids have an extremely high rate of reproduction which enables insect numbers to develop very rapidly. When aphid numbers are high, plants are stressed, and, therefore, less vigorous. Aphids damage the plant by piercing the leaves, stems, and flowers and sucking sap and other fluids. Consequently, plants are weakened, discolored, and stunted. Foliage may look puckered or distorted. Aphids tend to congregate on new plant growth in the early spring; curled, distorted leaves are usually good indicators that aphids are present. Lush plant growth is very attractive to aphids, and it has been noted that high nitrogen fertilizer rates can increase aphid reproduction.

Aphids have many natural enemies that successfully attack them and provide very effective control. They comprise a favorite part of the diet for ladybird beetles. Ladybird beetles eat entire aphids and can consume up to 100 aphids per day. Parasitic wasps are also very successful in destroying aphids. The wasp stings the aphid, and, in doing so, deposits her egg inside the aphid’s body. The wasp egg then hatches into a larva that grows and consumes the aphid’s internal body. The larva pupates inside the aphid and emerges as an adult wasp through a small exit hole it chews through the aphid’s outer skin. After the wasp emerges, the aphid’s corpse is referred to as a "mummy." Aphid mummies are good indicators that parasitic wasps are at work in the garden. Other predators include lacewings, syrphid flies, and assassin bugs. Encourage natural enemies of aphids by using synthetic insecticides as little as possible. Before treating any plants, thoroughly inspect the plant for the presence of natural enemies.

Aphids can be knocked off the plants with a strong jet spray of water. Insecticidal soaps or horticultural oils also work well to control aphids. It is best not to apply insecticidal soups or horticultural oils in direct sunlight as they can have phytotoxic effects on the plant. Heavy aphid infestations can be difficult to control if aphids hunker down in the folds of leaves, flower buds, or new growth. Pruning and disposing of aphid infested plant material can reduce aphid colonies. They can also be controlled by squashing with fingers.

For more information on web producing insects, refer to MU Extension Guide G7271 ( http://muextension.missouri.edu/xplor/agguides/pests/g07271.htm). For information on aphid control, see MU publication M145, Controlling Tree and Shrub Pests, or MU Guide G7274, Aphids, Scales and Mites on Garden and Landscape Plants.

Mary Kroening, Missouri Master Gardener Coordinator and UMC Horticulturalist (573) 882-9633