Cabbage Root Fly Remedies

Life Cycle

• Female cabbage flies lay their eggs near the vegetable plants’ stems. The eggs hatch in April and May, and the maggots burrow into the soil to feed on the plants’ roots for the next three weeks. Maggots then enter the pupa stage and emerge a week later as adult cabbage root flies that typically lay eggs six to seven days after emergence. The cycle continues throughout the growing season with three to four generations until the weather heats up. The cycle may begin again in the fall, when temperatures drop and the final pupae overwinter in the soil.

Symptoms

• The first symptom you may notice is a wilted plant -- a symptom that mimics nutrient deficiencies. If not stopped, the infestation leads to the death of the young brassica. Older plants are better able to tolerate light infestations. When pulled from the soil, the plant either has no roots or those that remain may be black. You may also find some cabbage root fly maggots still attached to, or inside, the roots.

Solution

• Pest management specialists at University of Massachusetts Amherst suggest using a chlorpyrifos-based insecticide soil drench to fight the cabbage root fly’s maggots. Aim the drench toward the base of the plants, and use a sufficient amount of water to soak the product to the plant’s roots. Read the insecticide label carefully to determine how close to harvesttime it can be safely used. You may need to reapply the insecticide a week later, so check the area carefully for maggots.

Prevention

• Create a barrier to keep the cabbage root fly maggots off the brassicas. Cut a waxed, cardboard milk carton into 2-inch squares. Cut from one edge to the center and use this opening to slide the square around the brassica’s stem. Pat the cardboard onto the soil. This prevents the cabbage fly maggot from laying its eggs on the soil at the base of the plant. Till the soil in the fall to bring the pupae to the surface. This exposes them to birds and other predators, and while it may not cure an infestation, it helps to cut down on the number of maggots.