Protect against tuber blight to the end

UK - August 05, 2004

Desiccating potatoes, whilst maintaining tuber blight protection right to the end of harvest, has become more difficult with the complication of adjuvants and blight products, and the trend to split the dose of desiccation treatments. The grower requires thorough destruction of the haulm with continuous protection against tuber blight right through to lifting, warns Dow AgroSciences.

“We no longer have tin fungicides as the last one or two blight sprays in the blight program and so are using products such as Electis* that prevent zoospore production in a different way. The mature and dying potato foliage acts as a major source of zoospores, which can drop off the leaves onto the soil through which the tubers will be lifted. Ideally, an effective blight programme will prevent zoospore production in the first place, but this protection needs to extend right through the desiccation process,” advises Paul Savage of Dow AgroSciences.

The trend towards split applications of desiccants, where the first desiccant spray kills the potato foliage, exposing the lower leaves and stems, and the second spray desiccates more thoroughly, has complicated this process. This practise can lead to the crop being exposed to blight infection for a longer period of time and could increase the risk of tuber blight.

“The choice of blight fungicides late in the program can make a big difference in the overall fight against tuber blight. This is because not all products have good activity on zoospores and not all fungicides are compatible with desiccants.” adds Paul.

“The zoxium in Electis adversely affects zoospore release, resulting in the production of non-motile spores, incapable of infecting tubers. When used repeatedly in a suitable program, Electis protects against tuber blight and can be tank mixed with diquat, glufosinate and carfentrazone-based desiccants, protecting tubers right through to lifting” concludes Paul Savage.