Maize leaf blight (Turcicum/Maydis)
Long boat-shaped grey-green to tan lesions (turcicum) or smaller spots (maydis) that dry the leaves and cut grain fill.
- Pathogen
- Fungi (Exserohilum / Bipolaris)
- Spreads by
- Air- & rain-splashed spores; debris
- Favoured by
- Warm, humid, wet weather; leaf wetness
- Main risk
- Leaves dry; poor grain fill, yield loss
Overview
The leaf blights are among the most important foliar diseases of maize (and affect sorghum). Turcicum leaf blight (Exserohilum turcicum) makes long, elliptical, boat- or canoe-shaped lesions, grey-green at first then tan/straw-coloured, that run along the leaf and enlarge and merge. Maydis leaf blight (Bipolaris maydis) makes smaller, more numerous tan spots, sometimes with a defined margin. Both start on the lower leaves and move up.
The damage is loss of green leaf area: a heavy attack, especially before and during grain fill (around and after tasselling/silking), dries much of the foliage so the plant cannot fill the cob, cutting grain yield and fodder value. They are favoured by warm, humid, wet weather with leaf wetness and by continuous maize and infected debris. Management combines resistant hybrids/varieties, rotation and residue management, and a protective fungicide from the first lesions where the crop is at risk.
How to identify it
- Turcicum: long, elliptical, boat/canoe-shaped lesions, grey-green then tan, running along the leaf and merging.
- Maydis: smaller, more numerous tan spots, sometimes with a defined margin.
- Both starting on the lower leaves and moving up, drying large areas of foliage.
- Worst before and during grain fill (around tasselling/silking), when leaf loss cuts cob filling.
What causes it and when
- The fungi Exserohilum turcicum (turcicum) and Bipolaris maydis (maydis), spread by air- and rain-splashed spores.
- Favoured by warm, humid, wet weather with leaf wetness, and by dense stands.
- Carry over on infected maize debris and are worse with continuous maize cropping.
- Build from the lower leaves upward and matter most around and after tasselling/silking.
Cultural & organic control
- Grow resistant/tolerant hybrids or varieties — the most effective and economical control.
- Rotate away from maize and manage/incorporate infected residue that carries the fungi over.
- Avoid over-dense stands and excess nitrogen, and keep the crop vigorous and balanced.
- Use clean seed and a bio-agent (e.g. Trichoderma) where recommended.
Chemical control
- Spray a CIB&RC-registered fungicide (e.g. mancozeb, or a recommended systemic) from the first lesions, especially as the crop approaches tasselling.
- Repeat as recommended in a wet, high-pressure season, and cover the foliage well.
- Rotate fungicide groups and observe the pre-harvest interval.
- Confirm the current product, dose and timing for your area with your local KVK.
Prevent it coming back
- Base the crop on resistant hybrids, rotation and residue management.
- Scout the lower leaves from mid-season and protect the crop before tasselling in a wet year.
- Avoid continuous maize, over-dense stands and excess nitrogen.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My maize leaves have long boat-shaped grey-tan lesions drying the leaves. What is it?
Those long, elliptical, boat- or canoe-shaped grey-green to tan lesions running along the leaf are turcicum leaf blight; smaller, more numerous tan spots are maydis leaf blight. Both dry the foliage from the lower leaves up and, if heavy before or during grain fill, cut cob filling and yield. Grow a resistant hybrid, rotate and manage residue, and spray a registered fungicide from the first lesions when the crop is at risk.
Why is the timing around tasselling so important for maize leaf blight?
Because the plant fills its cob using its leaves, and the leaf area around and after tasselling/silking is what powers grain fill. If leaf blight dries much of that foliage just before and during grain fill, the plant cannot fill the cob properly and yield drops sharply. Keeping the upper leaves green through this period — with a resistant hybrid and, if needed, a protective fungicide from the first lesions — is the key to protecting yield.
How do I reduce maize leaf blight without relying only on sprays?
Start with a resistant/tolerant hybrid, which is the most economical control. Rotate away from maize and manage or incorporate infected residue so less inoculum carries over, avoid over-dense stands and excess nitrogen, and keep the crop vigorous. These steps lower the disease pressure so that the protective fungicide you apply from the first lesions in a wet season works much better and may be needed less often.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.