Divisi
Potato tuber moth
Phthorimaea operculella · Insect
Photo: Ilia Ustyantsev · CC BY-SA 2.0
The potato tuber moth (Phthorimaea operculella) is a small, grey, night-flying moth whose caterpillar — not the moth itself — is the enemy of your potatoes. In the field it mines the leaves and kills shoot tips, but its worst damage is done to the tubers, the part you eat and sell: the caterpillar bores in and leaves silk-lined, droppings-packed tunnels that rot. It loves hot, dry weather that cracks the soil and bares the tubers, and it breeds on and on inside warm stores — so a small field problem can turn into a ruined store. It also attacks tomato and tobacco.
David Jones, University of Georgia, Bugwood.org · CC BY 3.0 us 
Caroline Harding, MAF · CC BY 3.0 au
Why it matters
This moth goes straight for the part you eat and sell — its caterpillar tunnels right into the tubers. A bad attack can wipe out up to 70% of your potatoes, first in the field and then all over again in the store. The worst part is that the caterpillars follow your harvest indoors and keep breeding in the warm store, so the loss grows week after week, generation after generation, long after the crop is lifted. Once it is loose in a store it is very hard to stop — which is why keeping it out and catching it early matters so much.
When to act
Adults caught in pheromone traps rising, or first mines seen in leaves; in store, any tuber tunnelling
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full potato tuber moth field guide
- Identify it
- Scout for it
- Control it
13 field-guide sections in the app
The full guide to potato tuber moth — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify potato tuber moth?
What you see first (in the leaves): pale, blotchy blister-like mines wandering through the leaves — patches where the caterpillar has eaten the soft green out from between the two leaf skins, so the leaf looks papery and see-through in blotches. Young shoot tips and stems get bored out, then wilt and die back (farmers call these dead shoots "dead hearts").
When should I take action against potato tuber moth?
Adults caught in pheromone traps rising, or first mines seen in leaves; in store, any tuber tunnelling
How do I control potato tuber moth?
Prevent it first — this is your strongest tool: plant clean, certified seed tubers so you don't carry the moth in from the start. Hill up deeply and re-hill whenever the soil cracks, so every tuber stays buried and out of the moth's reach. Where you can, irrigate to keep the soil from cracking open. Harvest promptly once the crop is mature and never leave lifted tubers lying out in the field — moths lay eggs on exposed tubers within hours. Where you can, rotate potatoes away from last season's plot.
Which crops does potato tuber moth affect?
Among the crops covered here: Irish potato, Tobacco, Tomato.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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