Dirty panicle of rice: grain discolouration symptoms and control

Photo at the top: Dark, discoloured grains on a rice ear. The fungus here is Sarocladium oryzae, one of the fungi behind dirty panicle, Photo: Donald Groth, Louisiana State University AgCenter, Bugwood.org, CC BY 3.0 US (cropped)

Quick answer

Dirty panicle of rice, also called grain discolouration, is a fungal disease of the paddy ear. Many fungi stain the husk and grain brown, black or pink, so grain fills poorly and loses price. It is worst when heading meets humid, cloudy weather. Manage it with clean seed, a label-approved fungicide around flowering and quick drying after harvest.

How to identify dirty panicle of rice

In Hindi it can be described as gandi bali (गंदी बाली, dirty ear), and in Telugu as ginja rangu maare tegulu (గింజ రంగు మారే తెగులు, the disease that changes grain colour). It is not caused by one fungus. TNAU (Tamil Nadu Agricultural University) lists more than ten fungi that are found on discoloured grains. They include Drechslera oryzae, the brown spot fungus, Sarocladium oryzae, the sheath rot fungus, and species of Curvularia, Alternaria and Fusarium. That is why the colour and the look of the spots change from field to field.

Grain discolouration symptoms

• Spots on the husk: dark brown or black spots and patches appear on the grains of the ear (panicle). They can cover part of the husk or the whole of it.
• Many colours: TNAU notes the colour can be red, yellow, orange, pink or black, depending on which fungus is involved and how bad the infection is. ICAR scientists describe ashy grey, black, pink and light brown types.
• Outside or inside: the stain may sit only on the husk, or the fungus may enter the rice kernel inside. When you dehusk a sample, a stained kernel shows the infection went deep.
• Chaffy and light grains: grains infected early often stay empty or half filled. In a bad attack the whole ear can rot.
• Whole ear looks dirty: unlike false smut, which hits one grain here and there, many grains on the same ear turn dull and dark. From the bund, affected ears look grey-brown instead of golden.

Look-alikes and how to tell them apart

• False smut: single grains turn into round, velvety balls, orange at first and greenish black later. The ball grows outside the husk and is bigger than a grain. Dirty panicle only stains the grain; it does not form balls. Read about false smut of rice and how to prevent it.
• Brown spot on the grain: brown spot makes oval brown spots on the leaves as well as on the husk. If the leaves carry many such spots, see our guide to brown spot of rice in paddy. The brown spot fungus is also one part of the dirty panicle complex.
• Sheath rot: the leaf sheath that wraps the young ear rots and turns brown. The ear comes out only partly or not at all, and its grains are stained. Look at the flag leaf sheath (the sheath of the top leaf) for the rot.
• Neck blast: the neck just below the ear turns grey-black and rots, so the whole ear turns white or falls over. The grains stay empty but are not spotted. See rice blast in paddy: leaf blast and neck blast.
• Grain-sucking bugs: the rice ear head bug (gundhi bug) sucks the milky grain. It leaves small brown feeding marks and partly empty grains. Shake the ears in the morning or evening and look for the long, thin, brown-green bugs with a strong smell.

Life cycle and when it attacks

TNAU explains that the fungi survive in infected grain, in rice straw and stubble, and in the leftovers of other crops. Their spores (tiny seeds of the fungus) travel by air and land on the ear when it comes out. So infected seed and crop waste left in or near the field are the main starting points.

The weather decides how bad it gets. TNAU names high humidity and cloudy weather at the heading stage, when the ears are coming out, as the main favourable conditions. Rain during flowering and grain filling keeps the ears wet and helps the fungi grow.

Infection can happen before harvest or after it. ICAR scientists at the National Rice Research Institute, Cuttack, note that fungi from the field carry on into storage. There they keep growing and can produce harmful toxins (poisons made by fungi). Wet paddy left in heaps after cutting, or grain stored damp, adds to the damage.

In Telangana and Andhra Pradesh the risk is highest in kharif paddy, when heading falls in the rainy, cloudy weeks. It can also appear in rabi if heading or harvest meets unseasonal rain. A thick, lush crop that stays wet for long is more at risk in any season.

Crops it attacks

Paddy (rice): dirty panicle is a disease of the rice ear. It starts at heading and flowering, and the damage builds up through grain filling and into storage. The loss is in both amount and quality. TNAU notes losses in both grain weight and grain quality. Stained grain fetches a lower price, and seed from such a crop germinates poorly. This guide covers paddy only.

When to act

We could not find an economic threshold (the disease level at which a spray starts to pay) for dirty panicle of rice from a recognised public source, so we do not give one. Plan around the crop stage and the weather instead:

• A stained grain cannot be cleaned by spraying. Fungicides only protect the ears and grains that are still healthy.
• TNAU gives 50% flowering (half the ears in flower) as the time for a protective spray. If heading meets humid, cloudy or rainy weather, and your field had dirty panicle before, treat it as a high-risk season.
• From booting (when the ear swells inside the leaf sheath) to grain filling, walk across the field twice a week. Look at the ears, the flag leaf sheath and the leaves for brown spots.

Grain discolouration control without chemicals

• Clean seed: use certified seed, or seed from a healthy crop. Do not keep seed from a field with stained grain. Discoloured seed carries the fungi into the next crop.
• Seed treatment: TNAU lists seed treatment with Bacillus subtilis (a helpful bacterium) at 10 g per kg of seed. Ask your KVK (Krishi Vigyan Kendra) for a good source.
• Neem oil spray: TNAU lists a 3% neem oil spray at 50% flowering, followed by a second spray 10 days later.
• Balanced nitrogen: too much urea makes a thick, soft crop that stays wet. Split nitrogen into several doses and follow a soil test. Our guide to nitrogen deficiency in plants explains how to read leaf colour before you top-dress.
• Spacing: use the recommended spacing for your variety, so air can move between the plants and the ears dry faster after rain or dew.
• Control other diseases and pests early: brown spot, sheath rot, sheath blight and grain-sucking bugs all leave the ears weaker and more open to the fungi.
• Field hygiene: remove and destroy infected ears and crop waste after harvest. Keep bunds and channels free of weeds and grasses.
• Harvest on time and dry quickly: cut the crop when it is ripe, not late. Thresh soon and spread the grain to dry in the sun. Do not leave wet sheaves or wet grain in heaps.
• Store dry: store only well-dried grain, in clean bags, off the floor and in a dry place. Damp storage lets the fungi keep growing.

Chemical control: fungicides for dirty panicle in paddy

Only the products below have paddy and grain discolouration (dirty panicle) on their official label or leaflet. Doses are per acre, worked out from the label's per-hectare dose. Where the label gives only a strength per litre, we say "dose as per label" and quote that strength. Spray one product at a time. Do not mix products in one tank. Cover the ears and the upper leaves well.

Paddy

Product	Contains	Label dose per acre	Water per acre	Wait before harvest
Merger Fungicide	Tricyclazole 18% + Mancozeb 62% WP	405–506 g	200 L	25 days
Motive Fungicide	Mancozeb 68% + Hexaconazole 4% WG	506 g	200 L	30 days
Avtar Fungicide	Hexaconazole 4% + Zineb 68% WP	405–506 g	200 L	34 days
GLOIT Fungicide	Propiconazole 13.9% + Difenoconazole 13.9% EC	Dose as per label: 0.07–0.1%, or 0.7–1.0 ml per litre of water	202 L (label: 500 L per hectare)	46 days

Notes from the labels:

• All four products hold two active ingredients in one pack. These are ready-mixed products approved on the label. They are not tank mixes.
• Merger: spray when the disease appears, in the morning or evening, with a high-volume knapsack sprayer. One to three sprays, depending on how bad the disease is. The label names brown spot, blast and grain discolouration on paddy.
• Motive: spray when the disease appears, at the vegetative and the productive stage, in the morning or evening, with a high-volume knapsack sprayer. One to three sprays, depending on how bad the disease is.
• Avtar: the label lists grain discolouration on paddy at 1000–1250 g per hectare in 500 L of water.
• GLOIT: the label lists dirty panicle (grain discolouration) on paddy at 0.7–1.0 ml per litre of water, with 500 L of water per hectare.

Check the waiting period first. The spray for dirty panicle goes on around flowering, and harvest is often only a few weeks away. Count the days from your spray to the expected harvest, and pick a product whose waiting period fits. Merger has the shortest wait (25 days) and GLOIT the longest (46 days). If the days left are fewer than the label's waiting period, do not use that product at that stage.

Rotate to avoid resistance

If you spray the same type of fungicide again and again, the fungus can stop responding to it. Fungicides are grouped by how they work, using the FRAC code (FRAC is the international Fungicide Resistance Action Committee). Change the group from one spray to the next.

FRAC group	Active ingredient	Products in this article
3 (triazoles)	Hexaconazole, propiconazole, difenoconazole	GLOIT (both parts), and one part of Motive and Avtar
16.1	Tricyclazole	One part of Merger
M03 (multi-site contact)	Mancozeb, zineb	One part of Merger, Motive and Avtar

Motive, Avtar and GLOIT all carry a group 3 triazole, so do not use them in back-to-back sprays. A simple plan: if the first spray was Motive or Avtar (groups 3 and M03), make the next one Merger (groups 16.1 and M03). Contact fungicides in group M03 carry a low risk of resistance, but they only protect the surface they cover. Keep to the number of sprays each label allows.

Safety and waiting period

• The waiting period before harvest (PHI, pre-harvest interval) for each product is in the table above. Count the days from the last spray.
• Wear gloves, a mask, full-sleeve clothes and boots while mixing and spraying. Do not eat, drink or smoke while spraying. Wash well afterwards.
• Spray in the morning or evening, not in strong wind or just before rain.
• Fish and water life: the Merger and Motive labels warn that they are toxic to water life. Do not use them near ponds, canals or fish culture.
• Re-entry: the Merger label asks you to keep out of the sprayed field for 48 hours, and the Motive label for 24 hours.
• Read the label and leaflet before use.

Frequently asked questions

What causes dirty panicle disease in rice?

A group of fungi, not a single one. TNAU lists Drechslera oryzae, Curvularia lunata, Sarocladium oryzae, Alternaria, Fusarium and several others. Their spores spread by air from infected grain and crop waste. Humid, cloudy weather at heading helps them most.

Can I clean discoloured grain by spraying?

No. A spray cannot remove the stain from grain that is already infected. It only protects the ears that are still healthy. That is why the protective spray goes on around flowering, and why drying and storing the harvest well matters as much.

Which fungicide is used for grain discolouration in rice?

Use one whose label lists paddy and grain discolouration. In our store these are Merger, Motive, Avtar and GLOIT. The doses are in the table above. Pick one whose waiting period fits the days left to harvest, and change the FRAC group between sprays.

Is dirty panicle the same as false smut?

No. False smut is caused by one fungus and turns single grains into velvety orange or greenish-black balls. Dirty panicle is caused by many fungi and stains the husk and grain brown, black or pink without making balls. Both are worse in wet weather at flowering.

Can I use seed from a crop with dirty panicle?

It is better not to. The fungi sit on and inside the grain, and stained seed germinates poorly. Use certified seed, or seed from a healthy field, and ask your KVK about seed treatment.

Related reading

• False smut of rice: symptoms, causes and control in paddy
• Brown spot of rice: symptoms, causes and control in paddy
• Rice blast in paddy: symptoms and control of leaf and neck blast
• Sheath blight of rice: symptoms, causes and control in paddy
• All paddy products
• All fungicides

Sources

• Tamil Nadu Agricultural University, TNAU Agritech Portal: grain discolouration of rice.
• Raghu S and others, ICAR-National Rice Research Institute, Cuttack, Emerging minor diseases of rice in Odisha: identification and management, Indian Farming 71(4), April 2021.
• Fungicide Resistance Action Committee, FRAC Code List 2026.
• Official labels and leaflets of the products named in this guide.