Divisi
Niger seed weevil
· Insect
Photo: xpda · CC BY-SA 4.0
The niger seed weevil is a small, hard-shelled beetle with a long, down-curved snout that attacks niger — the yellow-flowered oilseed grown for the oil in its little black seeds. The adults feed on the flower heads at flowering and seed fill, and their pale, legless grubs grow up hidden inside the heads, hollowing out the seed before it can fill. Warm, dry weather during seed fill favours it, and because the bored seed carries the weevil straight into your store — where it keeps eating and survives to next season — it is far easier to prevent than to cure once it takes hold.
Robert Webster · CC BY-SA 4.0
Why it matters
Niger is grown for the oil in its little black seeds — and that seed is exactly what this weevil eats. A bad attack can cost you up to a third of your harvest (about 30%), and it also lowers the oil content, so even the seed you save is worth less. The worst part is that the grubs grow up hidden inside the flower heads, where you cannot see them and no spray can reach — and the weevils then ride the bored seed into your store, where they keep destroying seed and live on to attack next season. That is why catching it early, at flowering and seed fill, matters so much — once it is in the heads and the store, it is very hard to stop.
When to act
Weevils feeding on heads or bored, hollow seed found when a sample of capitula is threshed at maturity.
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 niger seed weevil field guide
- Identify it
- Scout for it
- Control it
14 field-guide sections in the app
The full guide to niger seed weevil — 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 niger seed weevil?
Watch the damage first. As the yellow flower heads turn to seed, attacked heads carry nibbled feeding scars and look light, papery and half-empty — they set far less seed than healthy heads. Rub one open and the seeds are hollow and holed with tiny bore-holes — light, empty chaff instead of plump black seed.
When should I take action against niger seed weevil?
Weevils feeding on heads or bored, hollow seed found when a sample of capitula is threshed at maturity.
How do I control niger seed weevil?
Prevent it first — this is your strongest tool. Plant early and all at once, ideally together with your neighbours, so the crop flowers and fills seed before weevil numbers build up in the warm, dry part of the season. After harvest, clean up and destroy old niger heads, stalks and volunteer plants — this leftover residue is where the weevils survive between seasons (the 'carry-over'), so clearing it starves next year's attack.
Which crops does niger seed weevil affect?
Among the crops covered here: Niger seed (noug).
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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