Potato Review

20 POTATO REVIEW MARCH/APRIL 2021 WEED CONTROL T HE relatively recent loss of diquat coupled with unseasonal weather patterns and a move away from over-winter ploughing across much of Scotland has led to new challenges in early season weed control. A key example is the abundance of volunteer cereals in some potato crops according to Frontier agronomists Peter Forster and Steven Penrice. Based in East Lothian and advising on potatoes across Fife, the Borders and East Lothian for 11 years, Peter believes that last year’s major focus on desiccation without diquat overshadowed the product’s formerly pivotal role in early season weed control strategies. “Recent changes in weather patterns during winter and early spring, combined with a reduction in ploughing, have certainly contributed to higher weed pressure including speci c new challenges such as volunteer cereals,” he said. “Diquat would have dealt with many of these issues but we are where we are and the simple truth is that protoporphyrinogen oxidase (PPO) inhibitors cannot deal with volunteer cereals so many herbicide programmes now require a graminicide.” New control issues arises for Scottish growers following cultivation changes, adverse weather and aftermath of diquat Weed challenges in Scotland Another added complication when forward planning for eventual desiccation is when potatoes have followed a crop of brussel sprouts or cabbages. “Both these crops leave residual nitrogen in the soil, making early spring planning on fertiliser inputs more complex, given the added soil checks required before other input decisions can be made,” said Peter. With Scotland’s shorter growing season, it’s arguable that more detailed planning has always been required so the added complexities around early weed control have always been there (even before diquat’s demise), he added. “Despite the loss of some key actives I still see Praxim (metobromuron) as the foundation of my programmes. It has no “Diquat would have dealt with many of these issues but we are where we are and the simple truth is that protoporphyrinogen oxidase (PPO) inhibitors cannot deal with volunteer cereals so many herbicide programmes now require a graminicide.” Peter Forster Steven Penrice