Niger seed weevil

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.

is a small, hard-shelled beetle only a few millimetres long — about the size of a single niger seed — dull brown or greyish, with a long, down-curved snout at the front of its head (its mouth is right at the tip of the snout). Tap a head and it often folds its legs, plays dead and drops off, so hold a pale cloth or your open hand underneath to catch it and get a good look.

and look for the young stage deep inside: small, legless, C-shaped, cream-white grubs with a brown head, feeding on the seed right where no spray can reach them.

Bees and flies crowd niger's flowers for nectar but do no harm — they are pollinators, not the pest; the weevil is a hard beetle with a snout that actually bores the seed. And don't mistake it for bird damage (finches love niger seed): birds strip and scatter whole heads, while the weevil leaves the head standing but the seed inside holed and hollow.

start as soon as the crop comes into flower (mid-season) and keep checking right through seed fill to maturity (late season) — the whole window while the heads and seed are forming. Look hardest during warm, dry spells of about 20–30°C, the weather this weevil loves.

twice a week, walk a big "W" across the field so you cover all four corners and the middle, not just the edge by the path. Make about 5 stops along the W.

scan the flower heads for adult weevils and feeding scars, then tap several heads over a pale cloth or your open hand — the weevils drop off and are easy to spot. Then take a sample of about 10 heads, rub them out onto the cloth, and check the loose seed for bore-holes, light hollow seed, and grubs.

if you see weevils on the heads as you walk — or find bored, hollow seed in even 1–2 of every 10 heads you thresh — act now. Because the damage rides straight into your store, this pest has almost no safe level once the heads are forming. Check again at harvest and while threshing: live weevils in the threshed seed mean you must protect the stored crop too.

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.

As soon as the heads are ripe, cut and harvest promptly — ripe heads left standing in the field are a free meal, and the longer they stand the more seed the weevils bore. Getting the crop in on time denies them, with no chemical at all.

because the weevil follows the seed indoors. Dry the threshed seed thoroughly, then store it clean and sealed in tight drums, bags or containers. Good drying and sealed storage stop the hidden weevils from eating on — this protects the oil in your seed and stops them seeding next season's attack.

Where the attack is heavy, a pyrethroid spray can knock down the adults at flowering, before they lay their eggs in the heads. A pyrethroid is a contact insecticide — it kills the weevils it lands on but does not travel inside the plant (unlike a systemic, which is carried in the plant's sap), so it cannot reach the grubs already hidden in the heads. Handle it safely: cover your skin, eyes, nose and mouth, spray in the cool of the day with the wind at your back, keep it well away from food, drinking water and children, and wash yourself and your clothes afterwards. Respect the pre-harvest interval — the set number of days you must wait between your last spray and harvest so no poison is left on the seed.

Niger flowers are a magnet for bees, and this spray goes on at flowering, exactly when bees are working the crop. Spray only in the late evening once the bees have stopped foraging, never in open sun, and warn any neighbours who keep hives. To keep the spray working, rotate to a different chemical group in later seasons instead of using a pyrethroid every time — that stops the weevils building up resistance (surviving the spray so it no longer kills them).

If the heads are already heavily bored, harvest and thresh early to rescue the sound, filled seed before you lose more. Then burn or bury the badly bored heads and all crop residue so the weevils cannot survive to re-infest your store or next season's crop. Saving the good seed and destroying the rest breaks the cycle.