Diamondback Moth

A tiny pale green caterpillar, about a third of an inch, tapered at both ends, that feeds only on cabbage-family plants. It eats the underside of the leaf and leaves the thin top layer intact, so the leaf looks like it is full of little windows.

Pest15 plants we cover get diamondback mothmostly annuals

Pest checklist

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

Small clear windowpane patches in the leaf that let light through
A caterpillar the size of a grain of rice that wriggles hard and drops on a silk thread when disturbed
Loose silk webbing on the leaf underside
A small brown moth that shows three cream diamonds down its back when the wings are folded

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.

1Cover the crop
Insect netting or row cover over brassicas from transplanting on is the most reliable control, since the moths cannot get through to lay.
insect netting garden row coverTry this first
2Pull brassica weeds
Clear wild mustard, shepherd's purse and old brassica stumps from the garden edges; they carry the moths between crops.
3Spray Bt on small caterpillars
Bt aimed at the leaf undersides works well on this one and spares beneficial insects. Cover the underside of the leaf, not the top.
bt thuringiensis caterpillar spray
4Rotate any spray you use
This moth develops resistance quickly. If you go past Bt to spinosad, do not use the same product over and over.
spinosad garden insect spray

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Which plants get diamondback moth

Every plant we cover that gets diamondback moth, 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.

annuals15

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 15 of the 15 affected plants.

Brassicaceae15 plants

When to treat

Scout leaf undersides from mid-May on and treat while the caterpillars are small; this one shrugs off many insecticides, so covering the crop and using Bt matters more than spraying harder.

Timing only — the label is the law

This page tells you when to watch for diamondback moth 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.