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Home » Local Food & Farm Buzz, NHFN Updates

Leek Moth and Swede Midge Found in Home Gardens

By Piera Siegert, State Entomologist, Division of Plant Industry (December 1, 2016)

Two new vegetable crop pests have been confirmed in New Hampshire, thanks to a sharp-eyed home garden- er in Colebrook. Leek moth, Acrolepiopsis assectella, is a serious pest of Allium plants—onions, garlic, leeks, chives and shallots. Leek moth larvae develop and feed on the leaves of alliums, potentially resulting in stunted plant growth, introduction of rot, and reduction of the storage life of the bulbs. Visible signs of leek moth include characteristic “windowpane” or leaf miner-like damage to the leaves of host plants, and tell-tale frass (insect feces), debris, or larvae within the leaf. Leek moth is native to Europe, and was first found in Ontario in 1993. Leek moth was first detected in the continental United States in 2009 in Plattsburgh, New York. Since then, it has been found in counties in both eastern New York and northwestern Vermont. The first New Hampshire detection of leek moth in a home garden in Colebrook was recently confirmed.

The state’s first Swede midge, Contarinia nasturtii, was also detected in the same backyard garden in Colebrook. Swede midge is a Eurasian pest of crucifers like broccoli, cabbage, cauliflower and kale. Midges are very small flies and can be difficult to identify. The larvae feed on plant tissues and damage the plants by secret- ing a fluid that breaks down the plant’s cellular composition, allowing the larvae to readily feed on the liquefied plant material. This damages host plants in several ways—including puckered and crinkled leaves, swollen tis- sue of leaf petioles and bases, scarring at the growing point, distorted growing points, and establishment of rots at damage points. These symptoms can result from a variety of other causes, so where they occur, larvae should be collected to confirm the cause as Swede midge. Swede midge was first detected in Ontario in 2000, and has since been found throughout many counties in New York, and in isolated counties in Connecticut, Massachusetts, New Jersey, Ohio and Vermont.

In late July Dr. Alan Eaton, University of New Hampshire Extension Professor-Entomology, published an arti- cle in NH Vegetable & Fruit News entitled: “New insect pests in vegetable crops: leek moth and swede midge.” In the article, Dr. Eaton provided information about the damage caused by both pests, indicated that although nei- ther had yet been identified from New Hampshire, detections should be considered imminent, and asked anyone with symptomatic damage to report it to his team or to the Division of Plant Industry with the Department of Agriculture, Markets & Food. Within days of publication, this article resulted in a report of both leek moth and Swede midge to the Division. Division staff worked with the backyard gardener to set up pheromone traps and collect larval samples, which were then brought to the lab and reared to the adult stage for identification. Following the initial identification by New Hampshire entomologists, samples were sent to a national identifier for confirmation.

Alliums and crucifers are widely grown in New Hampshire on traditional and organic commercial farms, and in community and backyard gardens. This detection of leek moth and Swede midge by an astute backyard garden- er serves as both an example of effective communication and cooperation, as well as a notice to other growers  to examine their crops for signs of damage from either pest. If you believe you have seen leek moth damage in your alliums, or Swede midge in your crucifers, please contact: Alan Eaton at 603-862-1734 or email: alan.eaton@unh.edu. For more information about leek moth, Cornell University has developed this useful fact sheet: http://web.entomology.cornell.edu/shelton/leek-moth/index.html. Another helpful fact sheet by Cornell University for Swede midge can be found at: http://web.entomology.cornell.edu/shelton/swede-midge/index.html.

printed in NH Department of Agriculture, Markets & Food Weekly Market Bulletin, Nov. 30 2016

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