30 June 2009

A Cutworm Fence: protecting row crops from cutworm damage

Putting physical barriers, such as tin-foil or paper collars, around transplants is a common method of controlling cutworm damage. As immature larvae, especially in large numbers, the cutworms prefer small emerging seedlings, the kinds of row crops usually directly seeded into the garden. As the cutworms grow larger, they correspondingly prefer larger stems, including transplants which can easily be protected with collars or other physical barriers such as toothpicks or small nails stuck into the soil next to the stem.

To protect our emerging seedlings, such as carrots, parsnips, beets, greens and herbs, we built a cutworm fence as a physical barrier. We dug a 4 inch trench around the area, and drove small posts into the ground every 10-15 feet. A number of different materials could be used for the fence: plastic, feed bags, fabric, anything that will not let the cutworm pass through. We happen to have a large roll of woven fabric, similar to row cover, but in the future we would prefer heavy plastic (like the kind mini-homes are wrapped in, and can be diverted from the waste stream) because it is slick and more durable in the soil. The fabric was stapled to the posts, holding it taut to keep from sagging. It stretches 4 inches below the soil, and 6 inches above.

The cutworms can climb a short way onto the plant, but after observing them in our tin collection can, they cannot climb a vertical surface above 2-3 inches. And although they do burrow in the soil to feed, we have not seen any below 2-3 inches deep, and they do not travel below the soil.

We have observed that the cutworms quickly move from crop to crop within the garden. After we tilled under a heavily damaged crop of beet seedlings infested with cutworms, we noticed, only days later, that no cutworms could be found in the soil where no food was present. Therefore, we can easily exclude them from ground where we intend to sow direct seeded row crops by fallowing the ground in the spring, and constructing a cutworm fence prior to planting.

Since this barrier was erected after planting, we carefully cultivated the area and removed any cutworms we found, including disturbing the soil around the base of each plant by hand. We had been doing this regularly to control the population of cutworms in the garden, but this time, we can be sure that more will not move in from other areas of the garden. Most of the rest of the garden crops are either too large to cut (such as the beans and peas), or protected by nails along the stems (such as the transplants).

Cutworms travel above ground, mostly during the night, and can cover some distance searching for food. Though it does make them vulnerable to predators such as our fat and happy American Toad. We are currently building a small toad pool in the garden to encourage them to breed here.
The morning after we put up the cutworm fence, we were happy to discover very little damage overnight. The herbs were untouched, and only a few carrot and parsnip leaves had been cut, exposing the location of the remaining cutworms. Thank goodness, it seems that my war with the cutworms is drawing to an end. Practicing organic and ecological gardening means out-smarting, and out-maneuvering pests and diseases. I tend to be of the disposition to lock horns and butt heads directly with my pest-sized opponent, but this time it was simply wearing me down. So I learned an important lesson in gardening: to be nimble and adaptable in technique and method, to use my intellect instead of sheer determination and will-power. Determination got me through the steep beginner's learning curve, but now that I've got a few seasons under my belt, it's time to sharpen my tools and think like a gardener!
Other-where's in the garden, the perennial herb garden is flourishing, providing my first cut of Oregano, Thyme, Catnip and Alfalfa to dry for winter use.
We are also welcoming the butterflies back to the North. Including this White Admiral,

and a Monarch look-a-like: the Eastern Viceroy.

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