The Homeowners Column

The Homeowners Column

Improperly Constructed Compost Piles Attract Pests

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

Composting is a good thing as Martha would say. It recycles nutrients back
into the soil. Adding compost is also one of the best ways to improve a clay soil. Compost piles do not have to be smelly or attract bugs as some unconverted might believe.

However improperly constructed piles, piles that are not turned regularly
or piles that have thinner areas along the edges can provide refuge and breeding areas for some insects, according to U of I entomologist Phil Nixon. These cooler areas of the pile can harbor stable flies, house flies, and green June beetles.

Stable flies appear similar to house flies. They are grayish, about 1/4-inch long, and have black stripes behind the head and black spots on the abdomen. They can be distinguished from house flies by a needle-like beak that protrudes out in front of the head. If you don't see the beak, you may quickly feel its presence. The stable-fly uses this beak to feed on the blood of people and other animals.

Adult flies lay their eggs in wet straw, strawy manure, piles of grass clippings, and other decaying organic materials. The eggs hatch into small yellowish-white maggots (larvae). The maggots feed on the decaying organic matter. The maggots turn into pupae, emerging as flies 18 to 53 days after the eggs were laid.

Adult flies feed on blood, being most active biters in the morning and evening. Stable flies cause their victims to dance the fly dance, which is characterized by jumping and smacking of one's legs and ankles.

House flies are grayish, about 1/4-inch long, with black stripes behind the head, and the sides of the abdomen being pale in color. House flies do not have black spots on the abdomen, and their mouthparts are broad at the tip and project downward from the head. The house fly feeds on liquid food, using its mouthparts like a sponge.

Adult flies lay their eggs in moist, decaying organic material. They prefer fresh manure and rotting garbage, but will also use piles of lawn clippings and other organic debris. The eggs hatch into yellowish-white maggots. The maggots feed on decaying organic matter. The maggots turn into pupae, emerging as flies 6 to 20 days after the eggs were laid.

Green June beetles are robust, one-inch long, metallic green beetles with
yellowish margins on the wing covers. They are most common in the southern half of Illinois. The adults are strong fliers and make a loud, buzzing sound as they fly. They fly during the sunny hours of the day, frequently flying into people and whatever else is in their path. They feed on various kinds of fruits and vegetables such as peaches, nectarines, plums, apples, berries, and corn.

The beetles lay their eggs in organic debris. The eggs hatch into a white grub. The grubs feed on decaying material such as piles of grass clippings, hay, straw, the edges of compost piles, and turf areas with large amounts of thatch. They spend the day in the bottom of a burrow that is about one-inch in diameter and six to twelve inches deep. At night, they come out of the burrow and crawl around on their back.

Fully-grown larvae are almost two inches long and one-half inch in diameter. As winter approaches, the grubs dig their burrows deeper. In spring they resume feeding, pupating in late spring to emerge as adults in early summer.

Be sure to stop by the Idea Garden on South Lincoln for the workshop "Get the Scoop on Soils" on Saturday May 29 at 10:00 am . Find out what kind of soil you have in your garden and what you can do to improve it.

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