Now's the time for fungicides


15 September 2022
Don’t waste money storing rotten potatoes, growers warned.

WITH high disease risk and astronomical energy prices, seed potato growers should apply a fungicide to tubers now to avoid storing waste that will be thrown away next spring.

That is the advice of independent potato consultant Paul Overton, who added that tubers would likely spend extra time in store owing to uncertainty surrounding next year’s cropping plans. This will push growers to make last-minute decisions on seed and force a larger proportion of grading and delivery of domestic orders into March, rather than February. 

This extra month’s storage will only increase the already high risk of tubers breaking down to disease following a harvest where conditions have been very conducive for pathogens like Fusarium, he said.

The Fusarium species that infect tubers and cause dry rot are most prevalent when tuber damage at harvest is high, allowing the fungus to get under the skin and develop in store.

Paul said that despite conditions starting to cool and rain arriving to wet soils, the disease risk of dry rot is still very present, along with pink rot (Phytophthora erythroseptica) and watery wound rot (Pythium spp). 

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“Tuber temperatures are still 20C, or higher in some areas, which makes crops incredibly difficult to manage. It will be a slow process getting wounds to heal and crops down to cold store holding temperatures. The relatively warm nights aren’t helping either,” he said.

At today’s energy prices, this will also be a costly process, and likewise keeping crops in store until spring.

Paul said a good strategy in a high-risk year like this is to apply a “base coat” of a fungicide tuber treatment like Gavel (imazalil) as soon as possible after harvest. This will help protect open wounds and prevent disease ingress, leading to fewer losses at grading. 

“Storing tubers just to throw them out is very expensive – perhaps more than people realise – and the treatments will comfortably pay for themselves. Many varieties we grow are susceptible now and in very high-risk stocks, it might also be wise to consider mixing or sequencing Gavel with Storite Excel (thiabendazole) for additional protection,” he said.

He added that good coverage through sound application is key and recommended using a hooded sprayer with twin rotating nozzle over a roller table.

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