Researchers at the agribusiness company Sygenta have identified the amistar fungicide to help onion growers with the control of neck rot disease.
Amistar, a broad-spectrum containing azoxystrobin which inhibits the energy supply in fungi, has already had significant effects on salad onions in the control of leaf blight and collar rot, and now its potential to help with neck rot is being investigated. A research programme is being undertaken this season to verify its effectiveness and refine the optimum application timing of the systematic activity of the fungicide. “Apart from amistar, the only fungicides that have any activity against botrytis are protectant non-systematic material such as bravo, but they appear to have a limited efficacy against B alli which cause neck rot,” said field technical manager potato and vegetables, Jon Ogborn.
In order to reduce in-store losses from neck rot - unidentifiable at harvest - Sygenta recommend the best practical solution for bulb growers will likely be to apply amistar and bravo sprays in the early stages of the fungicide programme and to follow it up at the end of the programme.
“Initial treatment will provide persistent protection against downy mildew and prevent early neck rot infection…while the further application at the end of the programme will extend green leaf retention, maximising yield and improving skin quality,” said Ogborn.
“Given the difficulty of controlling neck rot disease, amistar rates should be maintained at one litre per hectare.” Trials using the amistar fungicide to control downy mildew have recorded up to 20tonne/ha improvements in bulb onion yields, while leaf blight infection was reduced to less than eight per cent of the leaf area in French trials, compared to 40 percent in unprotected bulb crops.
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