Divisi
Bruchids (bean and cowpea weevils)
Callosobruchus maculatus · Storage
Photo: limbatus · CC BY 2.0
Bruchids — the bean and cowpea weevils — are small brown beetles whose grubs live and feed hidden inside stored bean, cowpea, groundnut and pigeon-pea seeds. It starts quietly: females glue tiny eggs onto the pods as they dry in the field, or onto the grain in the store, and each grub bores into a single seed and eats it hollow from the inside before chewing its way out as a new beetle through a neat round 'window' hole. In a warm, humid store they breed again and again every few weeks, so a handful of beetles at harvest can turn a full store into powder within months.
limbatus · CC BY 2.0 
Originality1988 · CC BY-SA 3.0
Why it matters
Bruchids can wipe out your whole store — up to 100% of your beans — turning grain you meant to eat or sell into hollow shells full of powder, and spoiling seed so it won't even sprout. They do their damage hidden inside the seed, so by the time you spot the beetles and holes it is already done and multiplying. In a warm store their numbers double and double every few weeks, so a few beetles at harvest can eat out the whole stock in a single season. That is why keeping them out — clean, dry, airtight storage — matters far more than trying to kill them once they are in.
When to act
any adults, exit holes or eggs seen on stored grain
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 bruchids (bean and cowpea weevils) field guide
- Identify it
- Scout for it
- Control it
14 field-guide sections in the app
The full guide to bruchids (bean and cowpea weevils) — 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 bruchids (bean and cowpea weevils)?
The damage you'll see first: neat, round holes like tiny windows or portholes bored through the beans, and grain hollowed out and full of fine, whitish powder. Infested beans feel light and may rattle; scoop a handful and you'll see powder sifting to the bottom of the tin or sack. This grain fetches little at market, and if you plant it, it won't sprout.
When should I take action against bruchids (bean and cowpea weevils)?
any adults, exit holes or eggs seen on stored grain
How do I control bruchids (bean and cowpea weevils)?
Prevent it — start clean and dry. Harvest as soon as the pods are ripe; don't leave beans standing in the field to dry, where beetles fly in and lay their eggs. Dry the grain hard (a well-dried bean can't be dented with a fingernail or a tooth). Before storing, scrub out the store and containers and burn last season's leftover grain and pod trash where beetles hide. Never tip new grain onto old — store this season's crop on its own, and store only whole, unbroken beans.
Which crops does bruchids (bean and cowpea weevils) affect?
Among the crops covered here: Cowpea, Groundnut, Pigeon pea.
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.
Check what grows on your farm