Arhar (Tur)

Nitrogen (nodulation failure)

Visible symptom

Uniform pale yellowing and stunted, spindly growth despite a fertilized field — in a legume this almost always traces to poor or absent rhizobium nodulation rather than a genuine soil nitrogen shortfall.

Phosphorus

Visible symptom

Dark green to dull, sometimes purplish older leaves, delayed flowering and a poorly developed root system — arhar is notably responsive to phosphorus.

Sulphur

Visible symptom

Pale yellowing of the younger leaves first, since sulphur does not move within the plant — easily mistaken for a nitrogen shortfall, and common on light soils under a pulse.

Iron

Visible symptom

Interveinal yellowing on the youngest leaves while the veins stay green, most common on high-pH calcareous or temporarily waterlogged soil.

Zinc

Visible symptom

Small, narrow, bunched younger leaves with interveinal yellowing and shortened growth between nodes, often in patches on light or over-limed soil.

Fusarium Wilt

Symptoms

Gradual yellowing, wilting and death of the whole plant, often on one side first; a purple-brown streak runs up the inside of a split stem, and plants die in patches that widen year on year on the same land.

Cause

Soil-borne fungus Fusarium udum, which persists in the soil for years and enters through the roots — the single most damaging arhar disease, and one that no in-season spray can cure once a plant is infected.

Treatment

No effective in-season cure; remove and destroy wilted plants to slow the build-up of soil inoculum, but the real control is made before sowing, not after.

Prevention

Grow a wilt-resistant variety (Asha, Maruti, BSMR 736) matched to your land's history — this is the decisive control; add a Trichoderma seed treatment and a long rotation away from arhar on infected fields.

Sterility Mosaic Disease (SMD)

Symptoms

Bushy, pale, excessively branched plants with small mosaic-mottled leaves that flower little and set almost no pods — the "green plague" of arhar, since an infected plant stays alive and green but produces virtually nothing.

Cause

A virus (pigeonpea sterility mosaic virus) transmitted by the eriophyid mite Aceria cajani, not by seed or soil — which is why controlling the mite vector and, above all, growing a resistant variety matter more than anything sprayed on the leaf.

Treatment

No cure for an infected plant; rogue out and destroy affected plants early to cut the mite-borne source of spread.

Prevention

Grow an SMD-resistant variety (Asha, BSMR 736) where the disease occurs, remove volunteer and ratoon arhar plants that carry the virus and mite over between seasons, and avoid sowing next to an old, infected arhar stand.

Phytophthora Blight

Symptoms

Dark brown, water-soaked lesions on the stem and branches that girdle and collapse the plant; worst in low-lying, waterlogged patches after heavy rain, killing plants in wet spots.

Cause

Soil- and water-borne fungus Phytophthora drechsleri f. sp. cajani, favoured by heavy rain and standing water on poorly drained soil — a disease of drainage failure as much as of the pathogen itself.

Treatment

No strong in-season chemical cure once the stem is girdled; drain standing water off the field quickly to stop further spread through wet patches.

Prevention

Ridge or broad-bed planting and good drainage are the primary defence; avoid low, waterlogging-prone land for arhar, and use tolerant varieties where blight is a recurring problem.

Alternaria Blight

Symptoms

Concentric-ringed brown spots on leaves, and lesions on stems and pods, spreading in cool, cloudy, humid weather late in the season and causing leaf drop that cuts pod-filling.

Cause

Fungus Alternaria alternata / A. tenuissima, favoured by a humid, overcast spell during flowering and podding — most damaging on a late-maturing crop caught by early winter dews.

Treatment

A mancozeb or a suitable combination fungicide spray at first appearance, repeated if humid weather persists through podding.

Prevention

Avoid excessively dense stands that trap humidity, keep the wide row spacing the crop is designed for, and scout during any cool, cloudy spell at flowering.

Gram Pod Borer (Helicoverpa armigera)

Identification

Green to brown caterpillars, up to 3–4 cm, that bore a neat round hole into a pod and eat the developing seeds inside, often with the head thrust in and the body hanging out; the most damaging single pest of arhar.

Damage

Each larva destroys the seeds of pod after pod as it moves along a plant; an unchecked outbreak at flowering and podding is the largest single avoidable yield loss on this crop.

Organic control

Pheromone traps to monitor and time control, bird perches to encourage predatory birds, an NPV (nuclear polyhedrosis virus) or Bt spray against young larvae, and hand-collection of larvae on small plots.

Chemical control

A labelled insecticide such as chlorantraniliprole, flubendiamide or emamectin benzoate, timed to the young-larva stage at early podding — spraying only after larvae are large and deep inside pods is far less effective.

Spotted Pod Borer (Maruca vitrata)

Identification

A caterpillar that webs together flowers, buds and young pods with silk and feeds hidden inside the webbed mass, so the damage is easy to miss until buds and small pods are already lost.

Damage

Feeds on flowers and developing pods from within a protective web, causing flower drop and empty or bored young pods; the webbing also shelters it from contact sprays.

Organic control

Remove and destroy webbed flower clusters where practical, conserve natural parasitoids by avoiding unnecessary early broad-spectrum sprays, and use a neem-based spray against young larvae before webbing is heavy.

Chemical control

A spray targeted at flowering, before the larvae are sealed inside their webs — the same podding-stage insecticides used for Helicoverpa work if timing catches the exposed young larvae.

Pod Fly (Melanagromyza obtusa)

Identification

A tiny fly whose maggot develops entirely inside the pod, leaving no external hole — the damage shows only when a pod is opened to reveal a shrivelled, partly eaten seed and the maggot or its pupa.

Damage

Because it works invisibly inside intact-looking pods, pod fly damage is routinely underestimated until threshing reveals shrivelled, discoloured seed; it is worst on long-duration late-maturing crops.

Organic control

Few effective non-chemical options once inside the pod; growing an earlier-maturing variety escapes some of the late-season pod-fly build-up that long-duration crops attract.

Chemical control

A systemic insecticide at the early pod-formation stage, before maggots are established inside pods, since sprays cannot reach the maggot once it is sealed within an intact pod.