An early break in potato dormancy is likely to follow this year’s hot summer, say root crop agronomists.
Much will depend on update of sprout suppressant maleic hydrazide during the dry weather. Good uptake will help to delay any break of dormancy – but poor uptake will exacerbate the challenge.
“I haven’t yet seen any data on maleic hydrazide uptake, but I don’t see why it should have been horrendous,” says Norfolk-based independent agronomist Simon Alexander. “It was dry last year and we saw some quite good uptake. But with how hot it has been, in theory, we should see dormancy break earlier than normal, so careful monitoring of stores is going to be essential.”
A similar view is taken by independent potato agronomist Simon Faulkner, of SDF Agriculture. The accumulation of day degrees has been much higher than during a more normal year, he says.
Day degrees
“I suspect dormancy break will be sooner rather than later, which we are already seeing a little bit. That’s mostly tubers which have become green, so are ones closer to the surface and have accumulated more day degrees.”
Mr Faulkner stresses that testing is a valuable management tool, especially in this type of season. “If the tuber hasn’t taken up sufficient maleic hydrazide, it will be a candidate for earlier dormancy break, so there is some benefit of doing one or two samples.”
Both agronomists expect dormancy to break two to four weeks earlier usual. “It’s difficult to give a concrete answer,” says Mr Faulkner. “It will depend on varieties, on MH uptake, on whether they are cold stored or processing, warmer stored potatoes.
Processing potatoes
“Clearly, processing potatoes are at higher risk because you’re storing them at higher temperatures, whereas you will have more time with cold stores. Pulling temperatures down to 3°C clearly slows the process.”
Early lifted potatoes going into storage could also be at higher risk, suggests Mr Alexander. “Most growers start worrying about stores once they finish lifting, but it’s crucial those earlier lifted crops get due attention.”
This is particularly important where potatoes lifted into ambient stores. That’s because night-time temperatures remained high during the early part of the season which will have exacerbated the risk.
Mr Alexander is less concerned about crops that appear to be sprouting in the field – although both agronomists emphasise the need to monitor crops and remain vigilant for any signs of activity.
Watchful eye
“On some varieties, such as Agria, you can dig up plants and they’re hairy and have chits. I don’t believe that is conventional dormancy break, and I’ve never seen it have an impact on sprouting in store – so don’t panic if you do see it.”
Mr Faulkner adds: “Be vigilant – look around the stores, especially in areas where there could be slight variations in temperature where dormancy could break sooner and treat accordingly.
“You might end up needing one or two more applications than usual. When it comes to application, make sure stores are in a fit state in terms of dryness – no wet patches or condensation on the roof, for example.”
Attention to detail should standard practice in any year – but it is particularly important this year. Following best practice will increase the likelihood of good application efficacy, despite the potential of an early break in dormancy.
In-store programme
UPL potato technical specialist Geoff Hailstone advises growers to consider starting their in-store programmes with a product that uses a physical mode of action. “This approach maximises the crop’s natural dormancy,” he says.
“Unlike products which need to be applied ahead of sprouting, a product like Argos (orange oil) can be delayed until sprouts begin to appear, pushing back in-store treatments until it’s clear that crop dormancy is broken.
There are multiple in-store sprout suppressants, with each having notable benefits, says Mr Hailstone. Growers and store managers should select the product most appropriate to their own situation, he adds.
“I’d encourage them to build a programme around these based on the merits of the available products to reduce storage costs and maximise potato quality. The market is tough at the moment, and every little gain helps improve profitability.”