Brown Spot Control

Symptoms

Brown spot is caused by the fungus Bipolaris oryzae, also called Helminthosporium. It makes many small, round to oval brown spots on the leaves, often with a grey or whitish centre and a yellow halo, looking like sesame seeds scattered on the leaf. Spots also occur on the leaf sheath, grains and glumes, causing dark discoloured grains. It is strongly linked to poor, infertile or nutrient deficient soils and water stress.

Damage

Heavy leaf spotting reduces photosynthesis and grain filling, while infected grains are discoloured and lighter, lowering yield and quality. Brown spot was a major factor in past famine because it thrives on starved crops. Losses are usually moderate but can be high on nutrient poor soils, in drought stress and on susceptible varieties.

Organic & cultural control

Correct soil fertility, since brown spot is mainly a disease of starved plants. Add organic manure and balanced nutrients, and correct deficiencies of nitrogen, potassium and micronutrients. Avoid water stress and improve drainage. Use clean, healthy seed and treat seed with hot water or with Trichoderma or Pseudomonas fluorescens. Remove infected stubble and weed hosts.

Chemical control

Where infection is high, recommended fungicides include mancozeb, propiconazole, or a combination such as tebuconazole plus trifloxystrobin sprayed at the early spotting stage and repeated if needed. Correcting soil nutrition is essential along with any spray, because chemicals alone do not fix the underlying starvation. Always follow the product label dose, observe the pre-harvest interval, and consult your local KVK or agronomist before spraying.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Keep the soil fertile with organic manure and balanced nutrients, correct micronutrient deficiencies, avoid water and drought stress, use clean treated seed and tolerant varieties, and destroy infected residue. A well nourished, unstressed crop rarely suffers serious brown spot.