Purple patches with yellow margins are spreading on my onion leaves. How do I stop it?
How to control purple blotch in onion (pyaaz) crop?
RRamesh1yr ago · 449 views
3 Answers
🌾Farmer.in Krishi TeamExpert ✓1yr ago
Purple blotch (Alternaria porri) is best managed by combining spraying with field hygiene. Start protective sprays of mancozeb 75 WP at 2.5 g per litre or chlorothalonil, and switch to a systemic like difenoconazole if disease pressure is high. Add a sticker or a few drops of liquid soap because onion leaves are waxy and sprays run off. Spray at 10 to 12 day intervals, more often in humid weather. Rotate fungicide groups to avoid resistance. Reduce humidity by wider spacing and avoid evening irrigation. Remove and destroy badly infected leaves, follow crop rotation away from onion and garlic, and use clean seed. Balanced potash and avoiding excess nitrogen also make plants less susceptible. Always follow the label dose and the pre harvest interval printed on the pack.
GGorakh1yr ago
The sticker tip is real. On waxy onion leaves my spray used to bead up and roll off until I started adding a wetting agent, after which the same fungicide worked far better against the purple patches.
MMadhukar1yr ago
Watch out, purple blotch and the stemphylium leaf blight often come together in our Nashik humidity, and thrips damage opens the door for both. Keeping thrips down and not irrigating in the evening cut my disease a lot. If you are unsure which disease it is, take a leaf to your KVK before buying an expensive systemic.