Ascochyta blight

is small, tan-to-brown spots (lesions) on the lower leaves, stems and, later, the pods. They show up first low in the canopy, where the leaves stay damp, and during a cool, wet, cloudy spell.

each spot grows into a round or oval lesion marked with rings of tiny black pinhead dots — the fungus's fruiting bodies — set in circles, like a small target or dartboard. Scratch them: these black dots are sunk into the tissue and do not wipe off. That ring of black dots is the clincher.

dark, sunken lesions wrap right around the stems and girdle them, so the plant snaps and topples over (this falling-over is called lodging). Infected pods carry dark blotches, and the seeds inside come out stained, shrivelled or half-empty.

chocolate spot on faba bean makes small reddish-brown 'chocolate' flecks with no black-dot rings; grey mould is a fuzzy grey fur with no rings; rust makes raised orange-brown bumps that rub off as powder on your finger. Only Ascochyta gives the flat, spotted lesion with rings of black dots that will not rub off.

start scouting once the crop is bushing out and the canopy begins to close (the development stage), and keep it up hard right through flowering and podding (mid-season) into late season. Look hardest in the day or two after every cool, cloudy rain — damp weather around 10-25°C is exactly when the fungus moves.

cross the field in a big 'W' so you cover all four corners and the middle, not just the edge by the path. Give extra attention to low, shaded, thick or slow-drying patches, and to any crop sitting near last year's legume stubble — those spots go first.

make about 10 stops, and at each stop bend down and inspect 10 plants (100 in all). Check the lower and middle leaves, the stems — especially at the branch joints and near the base — and the pods, because it always starts low, where the plant stays wet.

You are not waiting for a big count. The moment you find even ONE plant carrying those ring-of-black-dots lesions during cool, wet, cloudy weather, protect the crop now, before the next rain splashes it through the canopy. One infected plant in a wet spell is your signal to act — do not wait for five or ten.

This is your single strongest and cheapest defence: a resistant or tolerant variety holds the disease back more than any other single step and is the cornerstone of managing Ascochyta. Ask your seed supplier or extension officer which line is resistant for your legume and your area.

The fungus travels on the seed, so sow certified, disease-free, treated seed, and never save or plant seed from a crop that had blight — that is exactly how it gets into next year's field.

Because it also survives on old stubble: rotate 3-4 years away from host legumes (chickpea, pea, faba bean, lentil); plant new crops well away from last year's stubble (spores blow on the wind); plough under, remove or burn infected residue; and don't sow too thick — a dense, always-wet canopy is what it loves, while wider rows let the wind dry the leaves.

In a wet spell, the moment you find the ringed black-dot spots: pull out and carry away the first one or two infected plants where you can (don't drop them back in the field), and get protection onto the healthy growth before the next rain — while it is still just a few plants, not a canopy full.

Understand what it is first: chlorothalonil is a protectant (contact) fungicide — in plain words, it lays a protective coat on the surface that stops new infections; it does NOT travel inside the plant and cannot cure a leaf that is already blighted. So it only pays if you put it on healthy growth before, or at the very first sign of, disease. Use it as a seed treatment and as protectant sprays from early flowering, timed to wet weather; and because it is only a surface coat, re-spray after heavy rain and as new leaves appear (fresh growth is not yet covered). Always respect the pre-harvest interval (PHI) — the set number of days you must wait between your last spray and harvest — so no chemical is left on the pods.

Cover your skin, eyes, nose and mouth; spray in the cool of the day with the wind at your back; keep the spray off food, drinking water, children, livestock and bees; keep people and animals out of the crop until it dries; and wash yourself and your clothes afterwards. Don't lean on sprays alone — pair them with the resistant variety, clean seed and rotation — and if you can get more than one fungicide group, rotate to a different group so the fungus never gets used to a single one.

If cool, wet weather holds and lesions keep climbing despite protectant sprays, keep the crop covered on a tight schedule after each rain, and never walk or move animals through the crop while it is wet (you carry spores on your legs and their feet). But if stems are already girdling and plants are lodging across the field, this crop cannot be saved — cut your losses: harvest what sound pods you can, do NOT keep any seed from it, and after harvest bury or remove the stubble and rotate to a non-host for 3-4 years so next season starts clean.