Food-Gardening Lessons From A Wartime Victory Garden

Visit the Gro Shop! merch hat Shop Merch

How Can I Protect My Potatoes From Cut Worms?

“What is the best way to organically protect potatoes from the fat, grey larvae that wiped out my potatoes last year? I forget the bug’s name, but I looked it up last year. My organic gardening book said to use bran bits and molasses.” Question from Kit of Fairless Hills, Pennsylvania

Answer: I think your pest is the cutworm. Cutworms (Agrotis spp.) are the destructive caterpillars of nocturnal moths, and there are many kinds that attack practically every vegetable crop, including potatoes. Cutworms are fat, gray and curl into a C-shape when disturbed. They tend to feed along the ground at night and are called “cut” worms because of their ability to cut off seedlings and small stems. They will also eat into tubers, roots, and fruits. Several cultural steps and products can help control them.

Cultural Steps to Stop Cutworms

Weeds are a cutworm’s first food, so keep your beds weed-free. Tilling has also be shown to smother and kill cutworms early in the season, so consider tilling your beds under before planting your potatoes. Placing plastic collars around the base of plants has also been shown to ward off cutworms. And, sprinkling a layer of food-grade diatomaceous earth around the bases of plants has also been shown to help. Diatomaceous earth has sharp points that we can’t feel, but these cut into the flesh of soft-bodied caterpillars.

Hand-picking also helps. Cutworms tend to hang out below plants in shady spots during the day. Look for them, and smash or drown them in a glass of water for easy removal.

Pesticides to Stop Cutworms

The use of molasses and bran traps appears to be one old-time method gardeners have used to kill cutworms. The theory is that cutworms are lured to the mix and trapped and/or damaged by the thick molasses. I cannot testify to this method, but I can advocate the use of BT (Bacillus thuringiensis), which is an all-natural insecticide approved for organic gardening. The beauty of BT is that it only damages harmful insects that chew on your plants. Bees and other beneficials are not impacted by BT.

Take some or all of these steps, and your cutworm troubles should be over.

Happy gardening,

Jessie Keith

Black Gold Horticulturist

About JESSIE KEITH

Plants are the lens Jessie views the world through because they’re all-sustaining. (“They feed, clothe, house and heal us. They produce the air we breathe and even make us smell pretty.”) She’s a garden writer and photographer with degrees in both horticulture and plant biology from Purdue and Michigan State Universities. Her degrees were bolstered by internships at Longwood Gardens and the American Horticultural Society. She has since worked for many horticultural institutions and companies and now manages communications for Sun Gro Horticulture, the parent company of Black Gold. Her joy is sharing all things green and lovely with her two daughters.

Leave a Reply

Content Disclaimer:

This site may contain content (including images and articles) as well as advice, opinions and statements presented by third parties. Sun Gro does not review these materials for accuracy or reliability and does not endorse the advice, opinions, or statements that may be contained in them. Sun Gro also does not review the materials to determine if they infringe the copyright or other rights of others. These materials are available only for informational purposes and are presented “as is” without warranty of any kind, express or implied, including without limitation warranties of merchantability, fitness for a particular purpose, and non-infringement. Reliance upon any such opinion, advice, statement or other information is at your own risk. In no event shall Sun Gro Horticulture Distribution, Inc. or any of its affiliates be liable to you for any inaccuracy, error, omission, fact, infringement and the like, resulting from your use of these materials, regardless of cause, or for any damages resulting there from.