New insect pests in vegetable crops: leek moth and swede midge

by Becky Sideman, UNH Extension Professor & Specialist, Vegetable & Berry Crops

We have a couple of new pests in New England. Neither have yet been documented in New Hampshire, but they are both present in Vermont and we expect that they will arrive here soon, if they are not already here. I wanted to remind you about these pests, and to ask that you keep a look out and let us know if you suspect that you have either of these. ***Jan 2017 update***As of early November, 2016, NH State Entomologist Piera Siegert let us know that both swede midge and leek moth have now been positively confirmed. Both were found in a garden in Colebrook. Please do keep us posted if you think you have these pests, as we are very interested in monitoring the whereabouts of this pest! – Becky

Leek Moth

Leek moth (Acrolepiopsis assectella) arrived in Vermont in 2012, and thus far it has been confirmed throughout the northern two-thirds of VT as far east as the NH border. Scott Lewins (St. Michael’s College) and Victor Izzo (UVM) continue to monitor for this pest in VT.

The caterpillar of this moth feeds on Alliums, including garlic, onions, and leeks. There are three generations of this pest, and it is active starting in very early spring (once the soil temperatures hit 50F) in cycles through mid-late August. As you pull your garlic, pay attention for signs of the damage. The damage can be confused with that caused by thrips, botrytis blight, and saltmarsh caterpillar – but it is distinct. There are some excellent photos of the damage in these three publications:

These publications also detail management tactics. In addition to chemical approaches, rowcovers and other methods of exclusion can be effective. Please let us know if you have damage that you believe is caused by leek moth; this will help us keep an eye on it and get the word out about management strategies.

Swede Midge

Swede midge was first identified in the U.S. in New York in 2004. It is now present in northwestern VT, western MA, and southern CT, and as with leek moth, we suspect that it is only a matter of time before it appears in NH.

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. 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:

Yolanda Chen’s lab at the University of Vermont is conducting research on organic management of swede midge. Elisabeth Hodgdon, a PhD student in the lab, suggests that crop rotation and insect exclusion netting may be somewhat effective ways to manage the pest. It is very important to know that you have this pest in order to design an effective management plan.

Please let us know if you have damage that you believe is caused by swede midge.

If you think you may have one of these pests, and would like us to investigate, please reach out to any member of the Vegetable & Fruit Team, or to Piera Siegert, the NH State Entomologist (contact info here).

This entry was posted in Integrated pest management, Pest Alerts, Vegetables and tagged , , , , . Bookmark the permalink.

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