Potato Review

www.potatoreview.com POTATO REVIEW JULY/AUGUST 2021 19 SPROUT SUPPRESSION Sprayer e ciency Nick says sprayer e ciency has also been key to helping growers apply MH during the sweet spot and improvements have been seen with newer liquid formulations like Crown MH. e long-established wettable granule formulation of maleic hydrazide, Fazor, requires the operator to rip open and tip multiple 5kg packs each treating up to 1ha. As these granules need more aggressive agitation to ensure they are fully dissolved, it is also prone to foaming, which can slow the lling process further. Nick says using a liquid formulation almost completely eliminates this issue, with 20-litre packs or 600-litre IBCs of Crown MH allowing the operator to just ll and go. A new label requirement this year sees the IBCs combined with a FasTran 850 closed transfer system, which simpli es and speeds up the lling process further still. “It means the operator can draw the chemical straight out the IBC and into the sprayer at the same time as the water, so once everything is in the tank, it’s simply a case of detaching the pipes and o you go,” said Nick. “It’s estimated that one to two extra loads a day can be achieved using the system, which is vital when you have a narrow window of application.” ‘More e ort put into planning’ Norfolk grower John Benton focused more attention to application of maleic hydrazide this year, with its role in his sprout suppression programme more prominent than ever. Growing about 180ha of processing potatoes exclusively for McCain, about 50% of his crop – made up of Russet Burbank and Maris Piper – goes into long-term storage. In the past, the business has used CIPC to good e ect, fogging its ambient box stores three or four times to control sprouting before those crops are moved between January and May. is reliance on CIPC ended in 2020, with John switching to ethylene gas delivered by the Restrain system as the main in-store sprout control method. e farm has used maleic hydrazide in crops destined for long-term storage for several years, but timing tended to be dictated by tuber size and ensuring as many were in the marketable fraction as possible before spraying. “Last year, we took notice of all the guidance coming out of the AHDB and recognised the need to maximise e cacy. We put a lot more e ort into planning application than we had before,” said John. Maleic hydrazide application checklist • Treat healthy and actively growing crops • Apply 3-5 weeks before haulm destruction • Spray on a cool day (<25C) when RH is >50% and no rain forecast for 24 hours • Avoid using mixing partners where possible • Use a higher water volume – 300-500-litres/ha recommended • Reduce forward speed of sprayer to 8-12kph “Not only was there more focus on the use of maleic hydrazide to help manage sprouting early in the storage period, but also the acceptance that application must be spot on.” Nick Badger, Crop Protection Commercial Manager, Frontier ➜ is meant predicting harvest date for each crop, counting back to expected skin set, then haulm destruction date. is calculation provided the farm with a window three to ve weeks prior to ailing. Early starts John said all his MH was applied in the last week of July and rst week of August, with the sprayer operator starting very early in the morning to avoid the heat of the day. A much higher water rate was used than previously and no irrigation water was applied 48 hours before or after application. All these factors optimised leaf coverage and the spray solution dried slowly on the leaf, maximising uptake by the plant. “We stick to a minimum of seven-day intervals with our blight programme and worked with our agronomist Matt Taylor to apply the MH as a standalone product in between sprays to avoid any interference with uptake,” said John. e farm also took advantage of liquid maleic hydrazide formulation Crown MH last year, having a 600-litre IBC at the spray store where the bulk of the lling took place. For outlying crops, 20-litre packs were used. “It has been much easier to handle than lots of boxes and we’ll certainly be using the IBC system again this year,” John said. In the past, John said it has been hard to tell how much sprout control the maleic hydrazide was providing, as CIPC programmes would start relatively soon after store loading. It was similar during the 2020-21 storage period when the Restrain ethylene system was switched on early. However, in a shared store where some of the farm’s Maris Piper was held alongside 500t of crisping potatoes, ethylene wasn’t an option owing to concerns over its impact on fry colour. No sprouting As the crispers were not loaded out until Christmas, the store remained untreated, and no signs of any signi cant sprouting was observed, and John believes they would have held for a few more weeks with MH alone. Ethylene was used soon after to see out the remainder of the season and the combination of Crown MH and ethylene as an in-store treatment has provided equal control to anything achieved with CIPC. John’s feeling is that the combination has been slightly cheaper than previous CIPC programmes in some stores and signi cantly cheaper than if the farm had relied on mint oil. “We are con dent about the job maleic hydrazide has done for us, particularly after seeing what it achieved with the Piper in the co-operative store. “ ere is no reason why it won’t remain the backbone of our sprout suppression programmes for the foreseeable future.” Farm facts • 1620ha of owned and contracted land • Soils range from sandy loam to sandy clay loam • About 180ha of processing potatoes grown for McCain • Varieties include Shepody, Innovator, Russet Burbank, Maris Piper and Royal • 50% of the crop goes into long-term box storage (Russet Burbank and Maris Piper)