Ask Your PCA: How do you manage beet armyworm in head lettuce?

Issue Date: October 8, 2008

By Dale DeShane, Bakersfield CAPCA member

Beet armyworm is a hot-season pest. We have two crops of lettuce in the Bakersfield area. Because it is a hot-season pest, we don't usually have beet armyworm in the spring, when we have cool weather. We plant that crop in November and December and harvest in March and April before it gets hot.

But with the fall crop it's a severe problem. It can kill the plants and reduce the stand. They get it in the Huron area, too.

Even if you are able to establish a good stand, beet armyworm can still be a serious problem.As the lettuce grows and starts to curl they can lay their eggs inside the wrapper leaves. If that happens you have lettuce that looks fine but when you peel the wrapper leaf it's crawling with worms.

From the rosette stage on you can't have worms inside wrapper leaves. Before the rosette stage the decision on whether to spray is based on the number of worms found, the stage of growth and your experience.

The beneficial insects are knocked down by frequent applications of some of the older products. In the hot weather we treat more often. If it gets ahead of you it can be a problem in a hurry.

Because it's a hot-season pest, some years you treat more than others. There are some years the pressure is such we treat every three to five days.

Fortunately with lettuce we have three or four materials and we alternate just to try to keep from having resistance.

We rotate depending on the stage of the crop and the number of other pests we have. Sometimes we also get cabbage looper and corn earworm.

Knockdown is always important because if you have beet armyworm in the lettuce they're not going to buy it. Most of the materials we've been using last between five and seven days.

A quick re-entry is real important too, because we have crews thinning, weeding and harvesting the lettuce. Some of the newer materials give us a four- to 12-hour re-entry period.

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item. Top