Stemphylium leaf blight
Small pale yellow water soaked spots on the leaves grow into long tan to brown blotches that dry the leaves from the tips.
Crops it strikes
What you see
When to act
In warm, humid weeks check the leaf tips and the side of the leaves facing the wind twice a week. Start protectant sprays at the first tan, water soaked streaks, and spray sooner in fields that had leaf blight the season before.
What to spray
Active ingredients only, never brands. The FRAC group tells how it works: switch to a different group next time, so the disease does not learn to survive it. Spray only when the damage is worth the cost, and only with products registered with the Fertilizer and Pesticide Authority for your crop. Follow the label. The Shopee and Lazada links only show who sells something with that active ingredient, not a recommendation of any seller or product.
Resistance: Stemphylium on onion has become resistant to the strobilurins (FRAC 11) and in places to iprodione (FRAC 2). Lean on triazole (FRAC 3) and SDHI (FRAC 7) mixes in turn with mancozeb or chlorothalonil.
How to prevent it
- Plant healthy sets and seedlings, and throw out any with yellow streaked leaf tips.
- Keep thrips and purple blotch down. The fungus moves fast into leaves already wounded or spotted.
- Water by furrow or drip and in the morning, so the leaves do not stay wet through the night.
- Rotate for at least three years with crops outside the onion family, and remove or bury old leaves after harvest.
- Do not overfeed with nitrogen. Soft, lush leaves blight first.
Where this comes from
Not sure it is this one?
Many diseases look alike. Send a photo to Anee, the smart farm technician in anee.io. She reads it with your crop, its age and the weather, and tells you what it most likely is and what to do first. In Tagalog or English.