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Potato growers are at risk of virus and disease if they do not follow an integrated approach to new desiccation regime.
This is according to experts in the Agriculture and Horticulture Development Board (AHDB), who are working on their third year of desiccation trials across a number of sites.
Results and observations at their trial sites have shown that the slower ‘kill’ achieved by the chemical and mechanical alternatives to diquat means that green stems and leaves can still be present up to three weeks after desiccation.
They have found that even very small amounts of green material remain a viable target for virus-carrying aphids and diseases.
Virus threat
In a recent AHDB webinar, seed growers were asked when they would apply their last insecticide to the crop. Fifty-nine percent of respondents said it would be over two weeks before a T1 desiccation spray.
“Not all growers will be thinking about virus threat when desiccating, but you can find aphids on green regrowth up to three weeks after your T1 spray,” said senior agronomist for Scottish Agronomy Eric Anderson.
“Systemic insecticides generally remain effective for 14 to 21 days, with pyrethroids only lasting seven days, so if your last insecticide was applied two weeks before desiccation, you’ve got a problem,” he continued.
While this is a particular concern for seed growers, ware growers must also be aware of this risk.
“Even for ware and processing growers, the presence of green leaves and stems means the threat of foliar and tuber blight, which needs to be managed,” Eric explained.
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