COMMON MAIZE (VUTTA) DISEASES & PESTS IN BANGLADESH Farmer's Guide: Symptoms, Prevention & Control ==================================================== 1. FALL ARMYWORM (FAW) - Spodoptera frugiperda ==================================================== Type: Insect pest (not a disease) SYMPTOMS - Semi-transparent "window pane" patches on leaves (early larval stage, seedling to early growth) - Holes in leaves and in the central whorl ("Infested Whorl") - Larval droppings (frass) accumulate in the whorl - Damaged, hollowed-out, or destroyed cobs with frass inside, from silking onward - Large larvae can defoliate a whole plant in a single night PREVENTION & CONTROL - Plant early with the first rains; avoid staggered planting dates - Use balanced fertilizer for healthy, vigorous plants - Keep field borders free of weedy grasses - Scout fields weekly from seedling emergence; check 10-20 plants at 5 spots per field - Action point: spray if more than 20% of plants damaged at knee-high stage, or more than 40% of whorls damaged at shoulder-high stage; do not spray at tasseling/silking - Hand-pick and destroy egg masses and larvae - Use pheromone traps (35-40/ha) for monitoring and mass trapping - Apply SNPV biopesticide (0.2 g/L water) every 10 days, 2-3 times - Release natural enemies such as Bracon hebetor wasps where available - Avoid broad-spectrum insecticides that kill natural enemies ==================================================== 2. TURCICUM LEAF BLIGHT / NORTHERN CORN LEAF BLIGHT ==================================================== Causal organism: Exserohilum turcicum (fungus) SYMPTOMS - Long, elliptical (cigar-shaped), greyish-green to tan lesions on leaves - Lesions run parallel to leaf veins and can merge, causing large areas of leaf to die (blight) - Severe infection can destroy most of the leaf area, reducing grain fill - Common in humid weather with moderate temperatures PREVENTION & CONTROL - Grow resistant/tolerant maize varieties - Rotate maize with non-host crops (e.g., legumes) - Remove and destroy infected crop debris after harvest - Avoid overly dense planting; ensure good air circulation - Apply a recommended fungicide (e.g., Mancozeb or Propiconazole-based) if disease appears early and weather stays humid ==================================================== 3. COMMON RUST OF MAIZE ==================================================== Causal organism: Puccinia sorghi (fungus) SYMPTOMS - Small, round to elongated, reddish-brown pustules scattered on both leaf surfaces - Pustules rupture and release powdery rust-colored spores - In severe cases, leaves turn yellow and dry prematurely - More common in cooler, humid weather PREVENTION & CONTROL - Use rust-tolerant varieties where available - Avoid very early or very late planting that exposes crop to prolonged cool, humid weather - Remove volunteer maize plants and crop debris after harvest - Apply fungicide if rust appears early and is spreading rapidly, especially on susceptible varieties ==================================================== 4. DOWNY MILDEW OF MAIZE ==================================================== Causal organism: Peronosclerospora species (fungus-like organism) SYMPTOMS - Young plants show pale green to yellow (chlorotic) streaking on leaves, running parallel to veins - Leaves may appear stunted, narrow, and twisted - White to greyish, downy fungal growth can appear on the underside of leaves in humid/wet conditions, especially in early morning - Severely infected plants are stunted and often fail to produce normal cobs PREVENTION & CONTROL - Use certified, disease-free seed; treat seed with a recommended fungicide (e.g., metalaxyl-based) before sowing - Avoid planting in low-lying, waterlogged fields - Remove and destroy infected plants early (roguing) to reduce spread - Practice crop rotation with non-cereal crops - Ensure good field drainage ==================================================== 5. BANDED LEAF AND SHEATH BLIGHT (BLSB) ==================================================== Causal organism: Rhizoctonia solani f. sp. sasakii (fungus) SYMPTOMS - Irregular, greyish-green, water-soaked bands/patches on leaf sheaths, starting near the base of the plant - Bands spread upward to leaves and can reach the cob under humid conditions - Infected sheaths and leaves rot and turn straw-colored - Cobs may also be infected, showing rotting and poor grain fill - Common in dense plantings with high humidity PREVENTION & CONTROL - Avoid excessive plant density; ensure proper spacing for airflow - Avoid waterlogging; ensure good field drainage - Remove and destroy infected crop residues after harvest - Rotate with non-host crops - Apply a recommended fungicide at the base of plants if disease appears early in humid seasons ==================================================== 6. STALK ROT (Fusarium / Bacterial Stalk Rot) ==================================================== Causal organism: Fusarium species (fungus) or bacteria, often following stress/damage SYMPTOMS - Lower stalk becomes soft, discolored (brown to black), and shows a rotten smell (in bacterial stalk rot) - Pith inside the stalk disintegrates, leaving the stalk hollow and weak - Plants wilt suddenly, and stalks can easily break or lodge (fall over) - Premature plant death, often near maturity PREVENTION & CONTROL - Avoid excess nitrogen and imbalanced fertilization - Ensure adequate potassium fertilization, which strengthens stalks - Avoid water stress and waterlogging; maintain balanced irrigation - Control stem-boring insects, since wounds allow the pathogen to enter - Harvest promptly once mature to avoid stalk rot–related lodging losses - Practice crop rotation and residue destruction after harvest ==================================================== GENERAL TIPS FOR ALL MAIZE DISEASES & PESTS ==================================================== - Start with healthy, certified seed; treat seed before sowing when recommended - Follow proper spacing and recommended seeding rate to reduce humidity buildup within the canopy - Balance fertilizer application; avoid excess nitrogen, ensure adequate potassium - Keep fields and field bunds free of weeds and volunteer plants - Rotate maize with non-cereal crops such as legumes where possible - Scout fields weekly, especially during humid or rainy weather and around key growth stages - Remove and destroy infected crop debris after harvest to reduce carryover of disease - When applying any pesticide or fungicide, wear gloves and a mask, and follow label instructions - Contact your nearest Department of Agricultural Extension (DAE) office or the Bangladesh Wheat and Maize Research Institute for the latest recommended varieties and chemicals