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Purple Blotch: signs and treatment in Jamaica
An Alternaria fungal disease affecting onions, prevalent in warm, moist weather. PlantArmor's crop guides list purple blotch as a common problem on onion.
Signs to look for
- Small, water-soaked lesions that turn brown/purple
- Concentric rings within the lesions
- Girdling and collapse of leaves
What to do
Crops it affects
Questions growers ask
How do I recognise purple blotch?
An Alternaria fungal disease affecting onions, prevalent in warm, moist weather. The signs to look for: Small, water-soaked lesions that turn brown/purple. Concentric rings within the lesions. Girdling and collapse of leaves.
What should I do about purple blotch?
Apply Mancozeb or Chlorothalonil preventatively. Reduce humidity by proper spacing. Always read the product label and observe the registered rate, re-entry period and pre-harvest interval before you apply any pesticide.
Which crops are affected by purple blotch in Jamaica?
PlantArmor's crop guides list purple blotch as a common problem on onion.
Check it in the field
PlantArmor's reference library works offline, so you can compare what you are seeing against it standing in the plot, then log the spray you use along with its re-entry and pre-harvest intervals. Free to use.
This description and treatment come from the same reference library the PlantArmor app uses in the field. Pesticide registrations and permitted uses change — always read the current product label and observe the stated rate, re-entry period and pre-harvest interval.