NEW RESEARCH has identified potential desiccation blind spots for potato growers.

Experts working on the third year of desiccation trails taking place at AHDB Farm Excellence sites have warned that potato growers are at risk of virus and disease threat if they do not follow an integrated approach to new desiccation regimes.

Results and observations at AHDB 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 sprays.

Even very small amounts of ‘green material’ remain a viable target for virus-carrying aphids and diseases, such as blight and gangrene.

In a recent AHDB webinar, seed growers were asked when they would apply their last insecticide to the crop – with 59% responding it would be over two weeks before a T1 desiccation spray.

Senior Agronomist for Scottish Agronomy, Eric Anderson, who is leading the trials at Milton of Mathers Farm near Montrose, said: “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. Systemic insecticides generally remain effective for 14 – 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 warned.

“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.”

The main challenge for ware growers is achieving adequate skinset, and research to date has shown this is possible without diquat, though there are some factors to take into account. Growers are recommended to stop irrigation seven days before desiccation and to aim for an early-mid morning application of desiccants, ideally on a sunny day.

AHDB field-based research and demonstrations on desiccation without diquat started in 2018 and has taken place on eight trial sites across Britain, giving growers a chance to see alternative methods on real crops and discuss results with researchers, agronomists and their peers.

There will be another digital meeting in September, where growers can review all results and observations at: