Chickpea Problems: Ascochyta Blight, Root Rot and Pod Borers

Ascochyta blight: the problem that decides the crop

If a chickpea crop fails to a disease, this is almost always the one. Ascochyta blight shows first as small tan or brown spots on leaves and stems, often with a darker margin and, on close inspection, tiny black dots arranged in rings within the spot. Those dots are the fruiting bodies, and the rings are diagnostic. Spots merge, stems girdle and snap at the lesion, and in a wet spell a whole row can collapse in ten days.

It spreads by rain splash and by wet foliage brushing against wet foliage, which is why it runs down a row in streaks rather than appearing evenly. It also travels on infected seed, which is how it arrives in a garden that has never grown chickpeas, and it survives on crop debris in the soil for two or three years.

Everything that works against it is preventive and most of it happens before the disease appears: wide spacing so the canopy dries fast, no overhead watering, never walking or working in a wet row, clean seed rather than seed saved from a crop that showed spots, and a rotation that keeps chickpeas off the same ground for three or four years. Once lesions are girdling stems in humid weather, there is no cure available to a home gardener and the realistic choice is to salvage what has already podded.

Root rots and wilts: a drainage problem wearing a disease's name

Fusarium wilt and the various root rots kill chickpeas one plant at a time. A plant yellows from the bottom, wilts on a hot afternoon and does not recover overnight, and when you pull it the taproot is brown or blackened inside instead of creamy white. Neighboring plants stay healthy for a while, then one of them goes the same way.

The organisms responsible live in the soil and are effectively permanent once present, but they only do real damage in ground that stays wet. Chickpeas are a dry-land crop with no tolerance for waterlogging, and a bed that puddles after rain will lose plants to root rot every year regardless of what else you do. Raised beds, deep cultivation before sowing and honest restraint with the hose deal with more of this than any treatment will.

Pull affected plants as soon as you are sure and put them in the bin rather than the compost pile. Then extend the rotation: chickpeas should not follow chickpeas, and ideally should not follow any legume, for three or four years on ground where wilt has appeared.

Pests: fewer than you would expect, and one that matters

The acid exudate on chickpea foliage deters most general feeders. Slugs largely ignore the plants after the seedling stage, rabbits and deer usually leave them alone, and the crop needs none of the netting that brassicas or beans demand. What you get instead is a small number of specialists.

Pod borers are the serious one. The caterpillars of several noctuid moths chew a neat round hole in the pod wall, put their heads inside and eat the developing seed, and because each pod only holds one or two seeds, a borer in a pod means that pod is a total loss. Look for the round entry holes and for dark pellets of frass caught in the foliage below. Hand-picking works at garden scale if you start when the first pods inflate; a bacterial caterpillar treatment applied to the foliage works if you get it on before the larvae are inside the pods, which is the whole difficulty.

Aphids colonise the growing tips, particularly on soft, over-fed plants, and matter more as virus vectors than for the sap they take. Leaf miners scribble pale trails through the leaflets and are almost never worth acting on. Birds and mice take sown seed and are worth a cloche over the drill until emergence; birds also strip drying pods late in the season, which is a reason not to leave a ripe crop standing longer than necessary.

Knowing when to cut your losses

There is a point in a wet season where continuing to nurse a chickpea row costs you more than it returns. If blight lesions are girdling stems across most of the row while pods are still flat, the crop will not fill, and the sensible move is to strip whatever green pods are usable, pull everything, bin the debris and put the bed to something else.

The judgement is different if the pods have already inflated. At that stage the seed inside is often sound even when the foliage is failing, and pulling the plants and drying them under cover salvages most of the harvest. Wet foliage on a dying plant will not improve, but seed that has reached full size will finish.

Do not save seed from any crop that showed ascochyta. Seed-borne infection is the commonest way the disease arrives in a clean garden, and the small saving is not worth reinfecting your own ground.

Bin diseased chickpea debris rather than composting it. Ascochyta survives on residue in the soil for two to three years, and a home compost pile rarely gets hot enough throughout to kill it.

Rotation, hygiene and what to record

Three practices carry almost all of the prevention: a three to four year gap before chickpeas return to the same ground, clean seed from a healthy crop or a fresh packet, and a discipline of never touching the plants when they are wet. Add generous spacing at sowing and you have removed most of the risk before the season starts.

Record the date you first saw any lesion and where in the row it appeared, because blight almost always starts at the same spot each year, usually the shadiest or least ventilated corner of the bed. Record whether the plants had been rained on or watered overhead in the week before it appeared. Over two or three seasons those notes will tell you plainly whether your problem is the bed, the spacing or the watering, and each of those has a different fix.