'Desiccation will pose biggest question'

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With planting for the 2020 potato season on the horizon, growers must begin planning this year’s crop now, before it is even sown, says Agrovista agronomist Jack Hoyles.

East Anglia based Jack annually advises on 800ha of potatoes covering South Lincolnshire, Cambridgeshire and Norfolk most of which is destined for the processing and pre-packed markets. He predicts that desiccation will pose the greatest single question for growers during 2020 with all viable options for destroying potato haulm presenting potential challenges for many growers.
“2020 could be the toughest year yet. Ensuring customers still achieve industry targets such as market size, market dry matter and fry colour with an ever decreasing number of chemicals will require significant agronomic changes to the way we currently manage the crop taking advanced planning to the next level,” Jack said.

During the 2019 season many growers understandably still used diquat as part of their desiccation strategy but new trials confirmed that both a “flail and spray” and chemical-only approach to burning down the crop over a longer period are both viable with advanced planning on canopy management. 
“Desiccation (with and without flailing) is viable as long as you can control canopy growth and I achieved excellent results last year using the 2 main stem desiccants; Gozai (pyraflufen-ethyl) and carfentrazone-ethyl as part of a 3-4 spray program designed to achieve full desiccation. As Gozai has a 14 day harvest interval it will be my first spray within the program sequence,” Jack said.

Growers will also need to consider varieties carefully, particularly if considering reducing nitrogen rates to manipulate canopy growth in order to senesce the crop earlier and it is here that Jack sees some potential hurdles. 

“Employing a fertiliser strategy on long season varieties such as Markies (a variety that many of my chipper’s grow) could be problematic. Markies have 12-20 tubers per plant so if you cut back too heavily on fertiliser to control growth and then there’s a dry spell in spring you run the risk of not achieving market size by focusing too much on canopy size. Variety selection is critical, but getting some luck with some warm dry summer weather to help senesce the crop naturally before harvest cannot be underestimated either,” he said.

For early season weed control Mr Hoyles believes filling the gap left by diquat should be far more straightforward given the chemical options available to growers.

“This year I will be basing my early season weed control around Soleto (metobromuron), my “go to” residual herbicide. Its 100% safe on all varieties and on all soil types so it takes all the guesswork out of the equation. With diquat no longer an option I will be partnering Soleto with Gozai as my key contact herbicide applying it at 0.4l/ha on its own 4 to 5 days before the crop emerges, or as part of a tank mix. Good application timing and keeping water volumes up to ensure good coverage are the keys. To achieve best results you must apply Gozai in a mix at 200l/ha of water. If Gozai is used alone and weeds are larger than 4 true leaves then methylated seed oil must be added. 

"Black bindweed has become a big problem weed for many of my growers in recent years but I’m confident that Gozai’s proven effectiveness on dealing with a broad spectrum of stubborn weeds (including black bindweed) should help avoid the need for a follow-up spray.”