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Index : Vegetable Gardening
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- 11. Worms Attack Fall Vegetable Gardens - Top
- Many home gardeners here in Southern Arizona. like planting and growing cool season vegetables in the fall. Broccoli, cauliflower, spinach, chard, kale many types of bib and leaf lettuce grow and produce well during the cool months. But gardeners need to be alert to some voracious worms that also thrive in our fall gardens.
The first garden pest of concern is the cutworm. This insect is a dull grayish brown worm, about 2 inches long when fully grown. Cutworms are larvae of dull-colored moths of various species. They feed, mostly on young vegetable plants, by crawling over the ground until they run into a young juicy stem. They then proceed to eat through the stem at ground level causing the young plant to fall over and die.
Cutworms feed at night and hide in the mulch or under stones or lumps of soil during the day. At night you may be able to find them using a flashlight. But even if you find some of the cutworms and destroy them, you may miss others. So the best control is to protect the young seedling plants themselves by providing a barrier to the cutworms.
Since they crawl along the ground to do their feeding, placing an obstruction between them and the stems of your seedling vegetables will ward off the cutworms. Make a barrier by using a paper or Styrofoam cup. Cut the bottom out of the cup and place it over the each young vegetable plant. Push the edge of the cup into the soil an inch or so. This will hold the cup firmly in place around the plant and prevent the cutworm from pushing it out of the way.
These cup rings should be placed around all vegetable plants at the time of planting or when seedlings emerge from the ground. After the young plants have grown for a couple of weeks, the cup rings can be removed. At this point, the stems will be too large and tough for the cutworms to eat.
The second insect that is a frequent visitor to fall gardens of the Southwest is the cabbage looper. This caterpillar grows to about 2 inches long, is light green with white stripes down the length of the body. It has three pairs of true legs behind the head, plus three pairs of false legs at the abdomen end. This arrangement of legs causes the caterpillar to crawl with a “looping motion, similar to that of an inchworm.
Adults of the cabbage worms are mottled grayish-brown moths. They lay their eggs on the leaves, either singly or in small clusters. The adult moths are nocturnal, so don’t expect to see them in the garden laying their eggs. Their greenish-white eggs hatch in a few days and the larvae begin feeding on the undersides of leaves, moving towards the center of the plant. On cabbage they eat into the center of the head.
Because these worms blend so well with the color of leaves they’re very difficult to spot. So it’s easy to miss some if hand-picking control measures are used. For this reason, and the fact that they can be numerous, the best method of control is to spray with Bacillus thuringiensis, commonly known as ‘BT’.
Because BT is a bacteria only active in caterpillars it has no harmful effects on beneficial insects, animals or the environment. When ingested by the caterpillar it acts by causing the cessation of feeding. Even though cabbage worms may live on a day or two after the application of BT, they will not continue to eat.
When applying BT, be sure to spray the undersides of leaves. That is primarily where the worms will be feeding.
As there can be several generations of cabbage loopers throughout the fall and winter months, additional applications of BT may be needed. Inspect your vegetable garden frequently for evidence of the presence of cabbage loopers, then spray as needed.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: October 3, 2004
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