Potato Review

40 POTATO REVIEW SEPTEMBER/OCTOBER 2019 Keeping our options open M ore than 400 people turned up to a muddy, but thankfully sunny, Potatoes in Practice , where the focus – both in the seminars and the plots – was on loss of chemistry. Scottish Agronomy’s Greg Dawson kicked off the former sessions looking at alternatives to diquat with a particular focus on the seed sector. With tolerances so low, especially for pre- basic crops where there is zero tolerance for blackleg and virus, one of the major risks in delayed haulm destruction is the possibility for disease to gain a foothold. “Some of the canopies on these varieties can be very vigorous,” Greg said. “We could potentially reduce nitrogen to manage canopy duration, but you have to be very careful then in terms of disease risk. “We know from previous research on high grade seed that rapid haulm destruction reduces fungal disease in the crop.” Including flailing in the desiccation process rapidly removes foliage but it is Potatoes in Practice focuses on alternative options for diquat and CIPC. not practicable in wetter seasons. Ensuring control of any subsequent regrowth is also essential to manage virus risk. There are of course other chemical options, which are currently being trialled on AHDB Strategic Farms, as well as at the James Hutton Institute and Scottish Agronomy, however it’s likely that any methods we use in future will be slower to destroy the crop than diquat. “Bulking will carry on after desiccation, as it does now,” Greg said, “but as desiccation will be slower it is likely to carry on for longer so growers will potentially need to burn down earlier to ensure the crop doesn’t breachmarketable size.” Under root cutting, something also now under trial, could potentially speed up the rate of haulm desiccation and stop bulking, but as yet we don’t know if it is practical option for high grade seed. Russell Whiteford of BelchimCrop Protection also tackled the subject of desiccation at a workshop held later in the day, a new addition to the event, where he discussed likely options post-diquat. He focused on flail and non-flail options and the difficulties growers may face if flail/spray is not an option. Out in the field there was also a number of desiccation-related plots as well as two machinery demos which were showcasing kit currently available for mechanical destruction. Another recent loss, more of an issue for the ware sector, is CIPC, and AHDB’s Adrian Cunnington outlined options for reducing sprouting in store without CIPC. “Firstly we’ll need to change the way we manage our stores, with more refrigeration and less ambient air,” Adrian said. “On the chemical side maleic hydrazide will have a very important role to play, and we have been trialling its use both individually, and in combination with other chemicals such as ethylene or spearmint oil.” However, in general these chemicals are more expensive than CIPC by some margin, and as they are very volatile they can be easily lost if store conditions aren’t closely controlled. REVIEW: POTATOES IN PRACTICE