Cutworms And Radishes

Cutworm Description

• Cutworms get their name from their destructive habit of cutting through the stems of new plants at ground level. The first evidence of their presence is a newly sprouted plant severed at its base and lying on the ground. Sometimes the plant disappears altogether. Cutworms are most often seen curled up just below the surface of the soil and close to plants. Working the soil in the spring usually turns up at least a few of these culprits as they lie in wait for new plants to eat. Each species displays different physical characteristics, such as the black cutworm (Agrotis ipsilon), named for its grayish-brown to nearly black color, and the variegated cutworm (Peridroma saucia) with yellow spots on grayish-black body. Cutworms found in the spring may have spent the winter in the soil or may be a new generation recently hatched from eggs laid on plants.

Damage

• Radishes are most affected by subterranean or tunnel cutworms, such as the black cutworm, which often cuts the plant off at ground level and drags it into its tunnel to consume it. The pale western cutworm (Agrotis orthogonia) also feeds below the soil, attacking roots and underground stems. These species may devour the developing roots of a radish plants, causing its death. Other types of cutworms, known as surface feeders, include the army cutworm (Euxoa auxiliaris) that invades gardens in large numbers, and the variegated cutworm, a climbing species that does its damage on the upper parts of a plant or vine.

Prevention and Control

• Preventive measures to discourage cutworms include placing collars around the base of plants. This can be in the form of strips of newspaper wrapped around the stems, paper cups with the ends cut out, empty toilet paper tubes or anything that can be inserted in the ground both below and above soil level. While this method may prove difficult for crops like radishes that are usually grown in large numbers and closely together, other measures, such as keeping the area weed free may be more practical. You can also try spreading diatomaceous earth, which is available at garden centers, around the base of plants to discourage adult moths from laying eggs. Crushed eggshells or coffee grounds may also be used for this purpose. Turning the soil in the fall destroys overwintering larvae as well as plants they can feed on.

Growing Radishes

• The recommended planting specifications for radishes are usually 1/2 inch deep and 1 inch apart. If cutworms are a problem, you may try planting them more closely together, or about 1/4 to 1/2 inch apart, which may improve your odds of not losing the entire crop. If you notice little to no damage, you can start thinning the seedlings to stand about 1 inch apart. Radishes can be planted in U.S. Department of Agriculture plant hardiness zones 2 to 10 either shortly before the past spring frost date or shortly after. Before planting, enrich the soil with aged manure or compost in an area that receives at least 6 hours of sunlight per day or you could end up with more leaves than radishes. As a cool-weather vegetable, radishes can be replanted in late summer for a fall or winter harvest.