Corynespora leaf fall
Brown spots with a yellow halo and darkened veins that look like fish bones, and the leaves yellow and fall out of season.
Crops it strikes
What you see
When to act
During refoliation after wintering, and all year in nurseries, check the young leaves of 10 trees per hectare every week. Spray the new flush when fishbone spots start to show in wet weather. Old, hardened leaves need no spray.
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: Corynespora cassiicola resists benzimidazoles (group 1) in many crops in Asia. Rely on mancozeb and group 3, and alternate the two.
On labels for it, but not advised
- Carbendazim: Corynespora resists group 1 fungicides in many crops. Use mancozeb or a group 3 instead.
How to prevent it
- Plant clones known to resist Corynespora, and replace or bud over highly susceptible ones.
- Feed the trees well after leaf fall, so new leaves come quickly and evenly.
- Collect and burn fallen leaves in nurseries and young plantings.
- Keep nursery seedlings spaced and their leaves dry, since spores spread in wet weather.
- Ease tapping on badly defoliated trees until the canopy recovers.
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.