Fusarium head blight

one or two straw-coloured, bleached spikelets on a head while the rest of that head — and the whole plant — is still green. The bleaching starts at a flower and spreads up and down the head, so you often see a head that is half-green, half-dead.

look closely at the base of the bleached spikelets for a faint pink-to-orange salmon-coloured crust of spores, especially after damp weather. That pink-orange colour is the fingerprint of this disease — few other problems paint the head pink.

open a bleached head and you find shrivelled, light, chalky-white or pinkish 'tombstone' kernels — thin and dead instead of plump. On a maize cob the same fungus shows as a pink-red mould starting at the tip.

with sun-scorch or frost (which bleaches whole heads evenly, with no pink crust and no shrivelled grain), or with normal ripening (which turns the WHOLE plant golden at once, not one head early while the plant is still green). The mix of early-bleached heads on a green plant + pink spore crust is what makes this disease.

The danger is set at flowering (heading) — the point when the part-grown crop pushes out its heads and opens their flowers. Watch the weather from the moment heads emerge: warm (20–30 °C) with rain, heavy dew, or muggy humid air during flowering is the trigger. In a susceptible crop, that warm-wet flowering weather is your signal to act now — you do not wait to count sick heads, because by the time you see them it is too late to spray.

The danger is far higher if there is old maize or cereal trash lying on the soil in or near the field — that trash is where the spores come from. A field flowering in wet weather next to maize stubble is the highest risk of all.

to see how bad it got. Walk a big "W" across the field so you check all four corners and the middle, not just the edge by the path. Make about 10 stops, and at each stop look at 10 heads — pull them close and check for bleached spikelets and the pink-orange crust.

Note how many heads out of the 10 at each stop are blighted. This does not tell you to spray now (that window has passed) — it tells you how much toxin risk is in this field, whether to harvest it separately and store it very dry, and how much to change your plan (variety, rotation, residue) before next season, which is the real fix for this disease.

if warm, wet weather threatens right at flowering, apply a triazole fungicide (the recommended chemical group — for example prothioconazole or tebuconazole). A fungicide is a protectant/systemic — meaning it must be on the head to guard the open flowers before the fungus gets in; sprayed after the head is already blighted it does nothing. Time it to early flowering and aim the spray onto the head for good coverage.

cover your skin, eyes, nose and mouth; spray in the cool of the morning or evening with the wind at your back so the mist blows away from you; keep it off food, drinking water, children and bees; respect the pre-harvest interval (the number of days the label says you must wait between spraying and harvest, so no chemical is left on the grain); and wash yourself and your clothes afterwards. To stop the fungus getting used to the chemical (resistance), rotate to a different fungicide group in other seasons rather than using the same one every time.

once heads are bleached there is no cure this season, so shift to saving the grain. Harvest the worst fields separately, turn up the combine's wind or winnow hard to blow out the light, shrivelled 'tombstone' kernels (they hold the most poison), and dry the grain fast and store it very dry so the fungus and its toxin cannot grow further in the store. Badly blighted grain should be kept out of food and animal feed. Then fix the root cause before next season — clear the residue, rotate, and choose a resistant variety — because with this disease, next year's prevention is the only real cure.