Here are tips on how to identify and get rid of cabbage root maggots.
What Are Cabbage Root Maggots?
Cabbage root maggots affect cabbage, cauliflower, broccoli, and brussels sprouts. (This group of vegetables is also known as ‘cole crops.’) Different types of root maggots also occur that affect carrots, onions, and other veggie crops. Because cole crops are cool-season vegetables, cabbage root maggots are much more prominent in Northern zones of the US. They are difficult to control, because they hatch and feed underneath the soil, so you may only know they are there when you notice stunted growth or wilting foliage.
How to Identify Cabbage Root Maggots
Cabbage root maggots are white, legless, and about 1/3 inch long. As with most maggots, they clump in groups and will feed voraciously on root systems of cole crops.
The cabbage fly is tiny, grey and fragile, and will emerge in early spring. It resembles a small housefly. After feeding for about 10 days, eggs are laid at the base of cole crop seedlings.
Eggs are about 1/8 inch and oblong, and laid in rows, usually in moist or shaded areas (eggs are susceptible to heat damage, another reason they are mostly found in northern zones). They can often be seen near the main stem in the soil.
Larvae hatch and tunnel through the soil to feed on the roots. After feeding, they become cabbage root fly pupae and prepare for the transformation to become cabbage root flies.
Photo Credit: Ian Bedford/GrowVeg.com. Cabbage root maggots in the pupal stage are a sign that you will soon have cabbage root flies in your garden.
Cabbage Root Maggot Damage
You will notice wilting leaves, and sometimes a hint of blue cast or yellow in the foliage. As the larvae tunnel through the roots, the plants will wilt and shrivel. If you pull up the damaged plants, you will see the tiny maggots on the roots. Inevitably, the plant will die. Cabbage root maggots cause the most damage in late summer.
Control and Prevention
How to Get Rid of Cabbage Root Maggots
If you see flies in the air, scout for eggs in the soil. Run your fingers through the top layers near the bases of your plants. Destroy any eggs found.
You can try installing ‘cabbage collars’ at the base of the stem. These can be made from cardboard and will simply be a skirt around the base of the plant. It protects the plants from egg laying.
Sticky traps in the garden are effective at trapping cabbage flies. They are available at most nurseries.
Check with your nursery about using nematodes as a biological control for root maggots. Another biological control are wasps, so leave them alone.
Carefully dig up your plants and swish their roots in cold water to remove the maggots, then replant them. Either allow the maggots to drown in the water or feed them to your chickens for a tasty snack.