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In recent years we have been seeing a small amount of a leaf blotch caused by a fungus called Gnomoniopsis. The fungus can also infect fruit, typically from the calyx end.
The fungus is a soil-dweller that splashes onto strawberry leaves when it rains. Given that it rained heaps last season in the plant-growing region, growers should be on the look out for leaf blotch on leaves growing after transplant.
Once present in a planting, fungal spores move by rain splash to new leaves and flowers. Spores form in tiny close-packed pustules which you can see on leaf blotches after incubation, and also on infected fruit. The bumps are spore-forming structures called “pycnidia”, and they look like tiny goose bumps, much smaller than strawberry seeds.
A tricky thing about Gnomonia is that it can cause fruit without noticeable leaf lesions, or vice versa. An inconspicuous leaf blotch can be the initial source of infection. It’s unlikely to be a problem in tunnels given that there should be no water splash there.
The most effective fungicide controls that we have for this disease are systemic fungicides that can be used before flowering, options like Octave (prochloraz) or Systhane/Validus (myclobutanil), both group 3. Neither of these chemicals have registration—use is at growers’ own risk.
After flowering the need to consider withholding periods comes in, and our only options are rated as moderately effective—carbendazim (Goldazim, 1 day WHP), thiram (2 days WHP) or captan (1 day WHP).