Diamondback moth (DBM) in cabbage and cauliflower: identify, when to spray, control

Photo at the top: A DBM caterpillar on a cabbage leaf. Note the thin, clear "windows" it leaves behind, Photo: Merle Shepard, Gerald R. Carner and P.A.C. Ooi, Bugwood.org, CC BY 3.0 US (cropped)

Quick answer

The diamondback moth (Plutella xylostella, often called DBM) is a small moth whose green caterpillars eat cabbage and cauliflower leaves from below. They leave clear "windows" and holes, and in a bad attack they spoil heads and curds. Set pheromone traps, grow mustard trap rows, and spray a labelled insecticide at the threshold, changing the group each time.

How to identify diamondback moth

In Hindi this pest is called heerak prishth patanga (हीरक पृष्ठ पतंगा). In Telugu it goes by its English name, written డైమండ్ బ్యాక్ మాత్. Its scientific name is Plutella xylostella. The damage is done by the caterpillar (larva), not by the moth. Turn the leaves over and look on the underside, mostly on the young inner leaves.

• Egg: very small, oval and pale yellow, laid singly or in small groups on the leaf, often near the veins.
• Caterpillar (larva): pale green and slim, and narrow at both ends. A fully grown one is only about 1 cm long. When you touch it, it wriggles backwards very fast and often drops from the leaf on a silk thread. This quick wriggle is the easiest way to know DBM.
• Pupa (resting stage): sits inside a loose, white, net-like silk cocoon stuck to the leaf. You can see the green or brown pupa through the threads.
• Moth: small and slender, grey-brown, about 1 cm long, with long feelers held forward. When the wings are folded, a pale wavy band along the back forms diamond shapes. That is how it got its name. The moths hide by day.

Damage signs

• Young caterpillars first tunnel inside the leaf for a short time. Then they come out and feed on the underside.
• They eat the soft leaf tissue but leave the thin upper skin. This shows as small, clear patches, like windows. The patches later dry and tear, so the leaf gets many small holes.
• In a heavy attack the leaves look like a net, with only the veins left.
• In young plants the caterpillars may feed at the growing point, so the plant forms a poor head or no head.
• In cabbage heads and cauliflower curds they leave holes and droppings, so the produce gets a lower price in the market.

Look-alikes and how to tell them apart

• Tobacco caterpillar (Spodoptera litura): larger and darker, with dark spots on the body. Young ones feed in groups and scrape the leaf, and older ones eat whole leaves at night. See our guide to Spodoptera (tobacco caterpillar) control.
• Semilooper: green, but it walks by arching the middle of its body into a loop. DBM does not loop. See how to identify and control semiloopers.
• Cutworm: a thick, dark caterpillar that hides in the soil by day and cuts young seedlings at the base at night. DBM stays on the leaves. See our cutworm guide.
• Aphids: small, soft sap-suckers that sit in colonies on the leaves. They do not make holes. See our aphid control guide.

Life cycle and when it attacks

The female moth lays her eggs on the leaves at night. The eggs hatch in a few days. The caterpillar feeds and grows for one to two weeks, then spins its silk cocoon on the leaf and turns into a pupa. A new moth comes out some days later. In warm weather the whole cycle takes only a few weeks, so there are many generations in one crop season and numbers can rise fast.

DBM likes dry weather. Heavy rain washes many young caterpillars off the leaves and lowers the numbers for a while. Where cabbage, cauliflower and other crops of the same family are grown one after another, the pest moves from crop to crop and from old fields to new ones. So it can be found in most seasons.

It feeds only on crops and weeds of the cabbage family (crucifers). In India it is a major pest wherever cabbage and cauliflower are grown, in the plains and in the hills.

Crops it attacks

Cabbage: attacked from the nursery to harvest. The most harmful stage is from planting to the start of head formation, when damage to the growing point and inner leaves can stop a good head from forming. Later, caterpillars bore into the head.

Cauliflower: attacked in the same way. The leaves get windows and holes, and caterpillars feeding on or near the curd leave holes and droppings that spoil it for sale.

DBM also feeds on other cabbage-family crops, such as mustard, knol-khol, radish and broccoli.

When to spray (economic threshold)

The economic threshold is the pest level at which spraying starts to pay for itself. For DBM on cabbage, TNAU (Tamil Nadu Agricultural University) gives it as 2 caterpillars per plant at the head-forming stage (TNAU calls it the primordial stage). Once or twice a week, check several plants across the field and count the caterpillars on the underside of the leaves and in the inner leaves.

We could not confirm a separate threshold for cauliflower from a recognised public source, so we do not give one here.

Diamondback moth control without chemicals

• Mustard trap crop: TNAU advises growing mustard with cabbage at a ratio of 20:1 (one row of mustard for every 20 rows of cabbage). The moths prefer to lay eggs on the mustard. TNAU advises spraying the mustard rows from time to time so the caterpillars do not spread into the cabbage.
• Pheromone traps: these traps carry a scent that draws male moths. TNAU advises 12 traps per hectare, which is about 5 per acre. They catch moths and show you when numbers are rising.
• Neem spray: TNAU advises a neem seed kernel extract (NSKE) spray after the head-forming stage.
• Bt sprays: TNAU also lists sprays of Bacillus thuringiensis (Bt) at the head-forming stage. Bt is a natural soil bacterium that makes caterpillars sick when they eat treated leaves. It acts only on caterpillars.
• Parasitic wasps: TNAU advises releasing a small wasp, Diadegma semiclausum, about 60 days after planting. The wasp lays its eggs inside DBM caterpillars. Ask your KVK (Krishi Vigyan Kendra) whether it is available in your area.
• Clean seedlings: check the nursery before transplanting and do not plant seedlings with caterpillars on them. Raise seedlings under fine insect net where you can.
• Field hygiene: after harvest, plough in or remove old cabbage and cauliflower plants and cabbage-family weeds. They carry the pest to the next crop.
• Protect natural enemies: small wasps, spiders and predatory bugs kill many DBM caterpillars. Avoid sprays that are not needed, so these friends survive.

Chemical control: insecticide for DBM in cabbage and cauliflower

Only the products below have DBM on that crop on their official label. Doses are per acre, as printed on the label or converted from the label's per-hectare dose. Use one product at a time. Do not mix products in one tank. Cover the underside of the leaves and the inner leaves well, because that is where the caterpillars feed.

DBM in cabbage

Product	Contains	Label dose per acre	Water per acre	Wait before harvest
Coragen Insecticide	Chlorantraniliprole 18.5% SC	20 ml	200 L	3 days
Aston Insecticide	Chlorantraniliprole 18.5% SC	20 ml	200 L	3 days
Mokin Insecticide	Chlorantraniliprole 18.5% SC	20 ml	200 L	3 days
OMG Insecticide	Chlorantraniliprole 18.5% SC	20 ml	200 L	3 days
Shenzi SC Insecticide	Chlorantraniliprole 18.5% SC	20 ml	200 L	3 days
Benevia Insecticide	Cyantraniliprole 10.26% OD	243 ml	200 L	5 days
Gracia Insecticide	Fluxametamide 10% EC	162 ml	200 L	5 days
Simodis Insecticide	Isocycloseram 9.2% DC	81–121 ml	200 L	10 days
Alecto Insecticide	Broflanilide 20% SC	51 g (printed in grams on the label)	200 L	1 day
Elpida Insecticide	Emamectin benzoate 5% SG	61–81 g	200 L	3 days
Gunther Insecticide	Novaluron 5.25% + Emamectin benzoate 0.9% SC	354 ml	200 L	3 days
Rimon Insecticide	Novaluron 10% EC	304 g (printed in grams on the label)	200–400 L	5 days
Intrepid - Insecticide	Chlorfenapyr 10% SC	304–405 ml	200 L	7 days
Quartz Insecticide	Fipronil 80% WG	38 g	200 L	15 days
Mahaveer Insecticide	Fipronil 5% SC	324–405 ml	200 L	7 days
Hamla 550 Insecticide	Chlorpyrifos 50% + Cypermethrin 5% EC	304 ml	200 L	5 days

Notes from the labels:

• Coragen and OMG: spray at ETL (economic threshold level), preferably in the leafy growth stage. The Coragen label allows no more than two sprays.
• Aston, Mokin and Shenzi: spray at ETL with a knapsack sprayer.
• Benevia: spray early, when young caterpillars have just hatched. Two sprays 7–10 days apart, early in the crop. Use the spray solution within 4 hours of mixing.
• Gracia: spray at ETL. Two or three sprays, 7–14 days apart, depending on the attack.
• Simodis: the label says "leaf feeder, DBM". First spray at ETL, one more after 10–15 days if needed, and no more than two sprays in a season.
• Alecto and Rimon: the labels print the dose in grams although both are liquids, so ask the store if you are unsure how to measure them. Rimon: spray when the pest attacks.
• Elpida: spray when you first see caterpillars, and repeat if needed. Use enough water to cover all the leaves.
• Gunther: spray at ETL in the leafy growth stage, with a hollow cone nozzle. Up to three sprays, 10 days apart.
• Intrepid: spray with a knapsack or power sprayer.
• Quartz: give more sprays only if the attack is severe.
• Mahaveer: first spray 30–35 days after transplanting or when the pest appears. Two or three sprays, 7–10 days apart.
• Hamla 550: spray at any crop stage when the pest is at a level that causes economic loss.
• Gunther (two active ingredients) and Hamla 550 (two active ingredients) are ready-mixed products approved on the label. They are not tank mixes.

DBM in cauliflower

Product	Contains	Label dose per acre	Water per acre	Wait before harvest
Evicent Insecticide	Emamectin benzoate 5% + Lufenuron 40% WG	24 g	200 L	3 days

Evicent: first spray at ETL, then one or two more sprays 10–15 days apart. It is a ready-mixed product with two active ingredients, approved on the label. In our label records, Evicent is the only product in our store with DBM on cauliflower. Use only a product whose label names your crop.

Rotate to avoid resistance

DBM is known around the world for becoming resistant to insecticides quickly. If you use the same group again and again, it stops working. Insecticides are grouped by how they act, using the IRAC group number (IRAC is the international Insecticide Resistance Action Committee). Change the group from one spray to the next.

IRAC group	Active ingredient	Products in this article
28	Chlorantraniliprole, cyantraniliprole	Coragen, Aston, Mokin, OMG, Shenzi, Benevia
30	Fluxametamide, isocycloseram, broflanilide	Gracia, Simodis, Alecto
6	Emamectin benzoate	Elpida; one part of Gunther and Evicent
15	Novaluron, lufenuron	Rimon; one part of Gunther and Evicent
13	Chlorfenapyr	Intrepid
2B	Fipronil	Quartz, Mahaveer
1B and 3A	Chlorpyrifos (1B), cypermethrin (3A)	Hamla 550

Coragen, Aston, Mokin, OMG and Shenzi carry the same active ingredient at the same strength. Treat them as one choice, not five. For example, if your first spray was Coragen (group 28), do not follow it with Benevia, Aston or OMG. Pick the next spray from group 30, 6, 13 or 2B instead. After Elpida, do not use Gunther next, as both carry emamectin benzoate. Keep to the number of sprays each label allows.

Safety and waiting period

• The waiting period before harvest (PHI, pre-harvest interval) for each product is in the tables above. Count the days from the last spray to the day you cut the heads or curds. It ranges from 1 day (Alecto) to 15 days (Quartz).
• Wear gloves, a mask, full-sleeve clothes and boots while mixing and spraying. Do not eat, drink or smoke while you work. Wash well afterwards.
• Spray in the morning or evening, not in strong wind or hot afternoon sun.
• Bees: fipronil, emamectin benzoate, chlorpyrifos and cypermethrin are toxic to bees. If you spray the mustard trap rows, do it when bees are not working on the flowers, and tell beekeepers nearby.
• Fish: keep sprays and washings away from ponds, canals and wells.
• Read the label and leaflet before use.

Frequently asked questions

Which insecticide is good for DBM in cabbage?

Use one whose label lists cabbage and DBM. On our store these are the 16 products in the cabbage table above, from several IRAC groups. No single product works for long against DBM, so change the group from one spray to the next.

Which insecticide can I use for DBM in cauliflower?

On our store, Evicent Insecticide lists DBM on cauliflower on its label, at 24 g per acre in 200 L water, with a 3-day wait before harvest. For other products, ask your local agriculture officer or KVK for one labelled for cauliflower.

Why does DBM come back soon after spraying?

Eggs and pupae are often not killed by a spray, so new caterpillars appear a few days later. Caterpillars on the underside of leaves and inside the heads can escape a spray that only wets the top of the leaves. And if the same group is used again and again, DBM becomes resistant to it.

How do I know it is the diamondback moth and not another caterpillar?

Touch the caterpillar. A DBM caterpillar is small, pale green and narrow at both ends, and it wriggles backwards fast and drops on a silk thread. Look also for clear window-like patches on the leaves and loose white silk cocoons on the underside.

Do pheromone traps control DBM on their own?

No. They catch male moths and warn you when numbers rise, but they do not stop a heavy attack. Use them with the mustard trap rows, field cleaning and the threshold given above.

Related reading

• Spodoptera (tobacco caterpillar): identify and control it
• Semilooper: how to identify and control it
• Aphid control guide for vegetables and field crops
• Cutworm: protect young seedlings
• All insecticides

Sources

• Tamil Nadu Agricultural University, TNAU Agritech Portal: Cabbage: crop production and plant protection
• Insecticide Resistance Action Committee (IRAC): Mode of action classification
• Product labels and leaflets of the insecticides listed above.