Potato Review

38 POTATO REVIEW MAY/JUNE 2020 MH: FOLIAR APPLICATION but my advice is to only use MH on a day when rain is not expected. You should be able to nd one in the two to three-week window and why add the extra cost?” said Fokke. is is backed by Simon, who said: “Growers have been thinking about how MH applications t around blight spraying and irrigation, but I think its increased importance without CIPC will require us to t the irrigation and blight spray around the MH in order to get the most out of it.” Secondary growth A nal consideration for application timing is secondary growth which occurs when crops are stressed. As temperatures cool and water arrives either through irrigation or rainfall, the crop starts putting energy into producing haulm rather than tubers which can dent yield and reduce dry matter content. Such conditions can also cause secondary growth below ground, manifested in chain tuberisation. Fokke says there is little growers can do if secondary growth occurs around June, but if it occurs in July an application of MH can help to stop it, but timing is again critical. Sprout suppressant regime Sprout suppressant cost (£/t) Packing (refrigerated @3.5C) CIPC (1 dose) 1.20 Maleic hydrazide 2.00 Spearmint oil (1 dose) 4.50 Ethylene 3.50 Processing (ambient @9C) CIPC (3 doses) 3.60 Maleic hydrazide + spearmint oil (3 doses) 15.50 Maleic hydrazide + ethylene 5.50 Maleic hydrazide + DMN (2 doses) 11.00 “Where applied just one day after a stress period, good results are not always achieved. It’s best to spray two or three days after and it can do a fantastic job of stopping secondary regrowth. In these situations, where rapid regrowth is occurring, a phytotoxic effect is sometimes seen after MH application. “However, this is not negative phytotoxicity, it is a positive, because it means the product is doing its job. Under normal conditions, you will not see any e ect in the crop” Additional benefit Fokke adds that Certis’ work in the Netherlands has shown MH treatments to signi cantly reduce weight loss in store. It could be argued this was irrelevant when growers could still use CIPC. However, in its absence where stores are old and not in the best condition to utilise volatile alternatives, MH can provide a means of slowing any weight loss that may occur. “When you apply MH, you should get less respiration in store and less water loss and that means more tonnes sold.” “When you apply MH, you should get less respiration in store and less water loss and that means more tonnes sold.” Fokke Smit Sprout control costs (Source: AHDB Potatoes. Based on 8-month storage period) Getting the most out of maleic hydrazide – key points • Maleic hydrazide can play a key role in sprout control programmes and reduce overall storage costs, according to AHDB research • Other bene ts include reduced secondary growth and volunteer potato control • Application timing and quality key in maximising performance Dos: • Apply to second early and maincrop potato varieties • Treat healthy and actively growing crops • Apply three to ve weeks before desiccation • Spray on a cool day (<25C) when RH is >50% and no rain forecast for 24 hours • Use a higher water volume – 300-500-litres/ ha recommended • Reduce forward speed of sprayer to 8-12kph Don’ts: • Apply too early (more than ve weeks before desiccation risks yield penalty) • Apply too late (within 3 weeks of haulm destruction) • Apply after the onset of senescence • Treat crops showing signs of stress (water/ disease/nutrient) • Spray in hot or dry conditions • Use with blight sprays or adjuvants “Maleic hydrazide is a reasonable sprout suppressant in its own right and it can certainly give sprout control for a matter of months.” Adrian Briddon

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