Armyworms

Striped caterpillars that hatch in big batches and move through a planting as a group, which is where the name comes from. They can go from unnoticed to a stripped row in a couple of days, usually in late summer.

Pest14 plants we cover get armywormsmostly annuals

Pest checklist

Four things to look for. If most of them match what you are holding, you are in the right place.

Many caterpillars of the same size on one plant or a short stretch of row
Leaves skeletonized or eaten to the midrib, spreading outward from one spot
Lengthwise stripes, and on some kinds a small dark spot just above the second pair of legs
Fresh green droppings scattered on the leaves below the feeding

What gets rid of them

Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.

1Pick off the cluster
Young armyworms stay bunched together. Snap off the leaf holding the group and drop the whole thing in soapy water.
Try this first
2Check for egg masses
Look for fuzzy gray egg patches on leaf undersides and on fences or posts near the garden, and scrape them off before they hatch.
3Spray Bt or spinosad early
Both work on small caterpillars. Spray in the evening and cover leaf undersides, where they feed.
bt thuringiensis caterpillar spray
4Keep grassy edges mowed
The moths lay in tall grass and weeds next to the garden, so mowing the border cuts the number that move in.

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Which plants get armyworms

Every plant we cover that gets armyworms, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same pest can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.

annuals13

bulb1

OnionAllium cepa

Plant families hit hardest

Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Brassicaceae, with 4 of the 14 affected plants.

Brassicaceae4 plants
Solanaceae4 plants
Amaranthaceae2 plants
Poaceae2 plants

When to treat

Check plantings weekly from late July through September and act the day you find a cluster, because these are only controllable while they are small and they get much harder to kill once they are near full size.

Timing only — the label is the law

This page tells you when to watch for armyworms and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.

Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.