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

Issue Date: October 22, 2008

 

Ron Riddle, Santa Maria PCA, CAPCA member

Armyworms, like the other worm pests, do the most damage in the fall spinach crops.

It is important to begin looking for armyworms on spinach as soon as you start getting a couple of true leaves. You can see the worms on the crop. You can also usually see the web that they leave.

If you see even a few of the worms you need to consider an application. It doesn't take very many worms to cause a problem. These pests will just eat up the crop. They'll eat holes in the leaves and just destroy the spinach.

According to the University of California Pest Management Guidelines, armyworms and other caterpillar pests feed on the crown of the spinach and can even cause enough damage to reduce stand establishment. The guidelines suggest that you begin monitoring nearby weeds even before the spinach seedlings emerge.

Quick knockdown is important in order to avoid economic damage to the spinach.

Because spinach is a high value crop with a low threshold for damage, beneficial insects are generally not as important in spinach as they are in some other crops. By the time the beneficial insects bring pests under control the damage may already be done.

Parasitic wasps can help to control armyworms. But the problem is that you can't wait for the wasps to build up to the point that they bring the worms under control. By that time there would be too much damage, and the crop would be unmarketable.

Spinach is only in the ground for 35 to 40 days. It is not like a tree crop or other, more-permanent crops where you have the time for beneficials to build their populations to the point that they give you some ongoing help controlling pests.

But resistance management is very important with worm control on spinach, just like it is with any pest. You have to rotate your materials. A quick re-entry period is also important and most of the newer worm control materials give us that. The newer materials generally have a 12-hour to 24-hour re-entry period, and even the older materials have pretty short re-entry periods.

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