Extension Logo
Extension Logo
University of Minnesota Extension
extension.umn.edu

Cabbage and onion maggots

Quick facts

  • Two important root maggot species found in Minnesota are onion maggots (Delia antiqua) and cabbage maggots (D. radicum).
  • Root maggots can occur in any year but are more common during cool, wet springs.
  • Infested plants can appear discolored, wilted or stunted.
  • Damage can be severe enough to kill affected vegetables.
  • Physical barriers, like row covers, are the best way to manage them.

How to identify root maggots

Adults

  • 1/4 inch long
  • Dark gray with dark-colored stripes 
  • They resemble small house flies

Larvae

  • Legless maggots 
  • 1/4 inch long 
  • Yellowish-white 
  • Shaped like cylinders, tapering towards the head
Onion maggot adult
Multiple cabbage maggot larvae feeding on the roots of cauliflower.

Plants attacked by root maggots

Onion maggot damage

Onion maggots attack

  • Onion
  • Garlic
  • Carrot
  • Radish

Cabbage maggots attack

  • Cabbage
  • Broccoli
  • Cauliflower
  • Brussels sprouts
  • Radishes
  • Turnips

Biology

  • Root maggots spend the winter as pupae in the soil.
  • In spring, the maggots transform into adult flies.
  • Adult females lay about 50-200 small, white eggs at the base of plant stems and in nearby cracks in the soil.
  • The eggs hatch within a week into small, legless, whitish maggots.
  • Maggots move into the soil and feed on the roots, root hairs and germinating seeds of crucifers or onions.
  • After feeding for three to four weeks, maggots convert into pupae in plant roots or the surrounding soil.
  • There are several generations per year.

Damage caused by root maggots

Cabbage fed on by cabbage maggots becomes stunted and discolored and eventually wither and die.
  • Root maggots have several generations in a year, but most of their damage is limited to early spring plantings.
  • Seedlings and transplants suffer more damage from root maggots during a wet, cold spring.
  • The maggots feed on roots and bulbs, creating tunnels.
  • Plants first begin to wilt and can become stunted and yellowed.
  • Heavily damaged plants can ultimately die.

Managing root maggots in home gardens

 | 

Managing root maggot on farms

 | 

Authors: Marissa Schuh, IPM Extension educator, Jeffrey Hahn, and Suzanne Wold-Burkness, College of Food, Agriculture and Natural Resource Sciences

Reviewed by Bill Hutchinson

Reviewed in 2022

Page survey

© 2024 Regents of the University of Minnesota. All rights reserved. The University of Minnesota is an equal opportunity educator and employer.