02/09/2026
🥬 DBM A.K.A DIAMONDBACK MOTH — A MAJOR ENEMY OF CABBAGE
Diamondback Moth (Plutella xylostella) Is one of the most important pests of cabbage and other brassicas.
The adult moth itself isn't what damages your cabbage.
👉 The larva (small green caterpillar) does the damage.
Young larvae feed on leaf tissue, often from the underside. As the infestation increases, you may see small holes, window-like patches and eventually heavily damaged or skeletonised leaves.
Severe attacks can affect cabbage head development and reduce both yield and market quality.
🔍 HOW TO IDENTIFY DBM
Look underneath cabbage leaves for:
• Small, slender green caterpillars
• Small holes or "windows" in the leaves
• Larvae that wiggle rapidly when disturbed
• Small grey-brown adult moths
• Small cocoons/pupae attached to leaves
DBM develops through:
EGG → LARVA → PUPA → ADULT MOTH → EGG 🔄 AND REPEAT
Under favourable conditions, the life cycle can be completed quickly, allowing multiple generations within one cropping season.
ACTIVE INGREDIENTS USED AGAINST DBM
Options available at Modern Bazaar include:
IRAC 28 — Diamides
Chlorantraniliprole
Cyantraniliprole
IRAC 6 — Avermectins
Emamectin benzoate
Abamectin
IRAC 22A — Oxadiazines
Indoxacarb
IRAC 11A — Microbial insecticides
Bacillus thuringiensis (Bt) (Ask for Halt)
Pyrethroids such as lambda-cyhalothrin and cypermethrin (IRAC 3A) may also be registered for caterpillar control, but DBM populations in many areas have developed significant resistance to older insecticide groups. Their effectiveness should therefore not simply be assumed.
⚠️ WHY DOES DBM BECOME SO DIFFICULT TO CONTROL?
DBM has a short generation time and a remarkable ability to develop resistance.
Imagine spraying:
Week 1 — Chlorantraniliprole
Week 2 — Chlorantraniliprole
Week 3 — Chlorantraniliprole
Week 4 — Chlorantraniliprole
You are repeatedly exposing successive DBM populations to the same Mode of Action.
Even changing brands doesn't necessarily solve the problem.
Brand A: Emamectin benzoate - GROUP 6
then
Brand B: Abamectin - GROUP 6
❌ You changed the active ingredient, but you didn't change the Mode of Action group.
A resistance-management programme should rotate effective insecticides from different IRAC groups, rather than repeatedly relying on one group.
🐛 TIMING MATTERS
Don't wait until cabbage leaves are full of large caterpillars and holes before taking action.
Scout regularly.
Check the undersides of leaves, particularly younger leaves and the growing point.
Young DBM larvae are generally easier to manage than established populations, and early detection gives you more management options.
And remember: spraying is only one part of DBM management.
Field sanitation, removal of brassica crop residues, controlling nearby brassica weeds, conserving natural enemies, appropriate use of Bt/biological options and avoiding unnecessary broad-spectrum insecticides can all help reduce DBM pressure.
💡 THE TAKEAWAY
Don't spray cabbage because you saw holes.
Find the pest.
Identify it.
Check the population.
Choose an appropriate active ingredient.
Check its IRAC group.
Apply it correctly.
Then rotate Modes of Action.
Good DBM management isn't about finding the strongest chemical it's about using the right tools at the right time.
⚠️ Always follow the registered product label, including crop registration, application rate, PPE, maximum applications and Pre-Harvest Interval (PHI).
