Divisi
Legume pod borer
Maruca vitrata · Insect
Photo: Charles J. Sharp · CC BY-SA 4.0
The legume pod borer (Maruca vitrata) is a small, night-flying moth whose caterpillars attack grain legumes — cowpea, pigeonpea, common bean and soybean — at the flowers and pods, the very parts you harvest. The young caterpillar spins silk to web flower buds and young pods into a bundle, hides inside, eats the developing seeds, then bores from one pod to the next. It strikes during flowering and pod-fill and thrives in warm, humid weather when the crop flowers over a long, staggered period. It is one of the most damaging pests of cowpea across sub-Saharan Africa.
Ravi Vaidyanathan · CC BY 3.0 
Ashokjbp · CC BY 4.0
Why it matters
This pest goes straight for the parts you actually harvest — the flowers and the seeds inside the pods — so a heavy attack can cost you up to 70% of your grain, more than two-thirds of the crop gone. The trouble is that the caterpillar hides inside a bundle of webbed-together flowers, or deep inside a pod, where no spray can reach it. Once it has bored in, it is almost impossible to kill — so the whole fight is won or lost in the short window while the crop is flowering, before the young caterpillars get inside.
When to act
larvae or webbing on flowers, or damage on about 1 in 10 flowering racemes at the onset of flowering
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 legume pod borer field guide
- Identify it
- Scout for it
- Control it
17 field-guide sections in the app
The full guide to legume pod borer — 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 legume pod borer?
The first thing you'll see is flower buds and young pods stuck together in a bundle by fine silk webbing, often with brown, sawdust-like droppings (called frass) caught in the web. Pull a webbed bundle apart and you'll find it eaten hollow inside. A little later, look for small round holes bored into the pods, with half-eaten seeds and frass packed in behind them.
When should I take action against legume pod borer?
larvae or webbing on flowers, or damage on about 1 in 10 flowering racemes at the onset of flowering
How do I control legume pod borer?
Prevent — plant early and all at once. Sow early and at the same time as your neighbours, and pick short-duration (quick-maturing) varieties, so the whole crop flowers together in one short window and finishes before borer numbers build up. A long, drawn-out flowering period is exactly what feeds this pest.
Which crops does legume pod borer affect?
Among the crops covered here: Cowpea, Green gram, Pigeon pea, Soybean.
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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