Pest Alert: Swede Midge

This invasive pest of brassica crops has been detected at several northern New Hampshire farms.

A new report of Swede midge has been confirmed this summer in Coos County, by our state entomologist, Piera Siegert. This confirmation included adult fly activity in pheromone-baited traps, While this invasive species was previously detected in Colebrook and North Stratford, Swede midge adults have not be found in southern regions of the state. NH's Division of Plant Industry continues to monitor vegetable farms for adult fly activity in Hollis, New Boston, Peterborough, Milford, and Litchfield. Please let us know if you have damage that you believe is caused by Swede midge.

Swede midge (Contarinia nasturtiiis a serious invasive pest of Brassica crops, including broccoli, cabbage and kale. Swede midge was first identified in the U.S. in New York in 2004. It is now present in northwestern VT and NH, western MA, and southern CT, and we expect that it will continue to move throughout the region. This pest is particularly troublesome for smaller-scale producers, particularly those that lack enough space for crop rotation.

The swede midge (Contarinia nasturtii) is a tiny fly whose larva feeds upon the growing points of plants in the Brassica family. This includes many crops, as well as many weed species. Of the Brassica crops, collards and broccoli are more susceptible than others, such as cabbage or Brussels sprouts. The symptoms are leaf puckering and scarring, and blind heads in the growing points, as is shown in the feature photo for this post (photo credit Elisabeth Hodgdon). They can be confused with mechanical injury, herbicide injury, and heat/cold stress. Some excellent photos of injury, and more information about this pest, can be found at these two sites:

Work done by Elisabeth Hodgdon in Yolanda Chen’s lab at the University of Vermont, suggests that crop rotation and insect exclusion netting may be somewhat effective ways to manage the pest.  Find more information in their publication, entitled Organic Management of Swede Midge, is a collaborative effort by the University of Vermont, Cornell Cooperative Extension, and the University of Guelph. 


Rebecca Sideman
Sustainable Horticulture State Specialist
Full Extension State Spec/Prof
Phone: (603) 862-3203
Office: Cooperative Extension, Kendall Hall, Durham, NH 03824

Heather Bryant
Fruit & Vegetable Production Field Specialist
Full Extension Field Spec
Phone: (603) 787-6944
Office: Cooperative Extension, Taylor Hall, Durham, NH 03824