Hot summer increases risk of potato dormancy break

Dormancy break in potatoes is predicted to occur two to four weeks earlier than usual this year, prompting growers to be extra careful monitoring crops during storage.

Independent potato agronomist Simon Faulkner says the accumulation of day degrees has been higher following the hot, dry summer, so a “sooner rather than later” dormancy break is on the cards.

“It’s difficult to give a concrete answer. The situation will depend on variety, maleic hydrazide uptake, and whether potatoes are cold or warm stored.”

See also: How spearmint oil fits into potato sprout control programmes

Simon notes there are already reports of dormancy break – mostly in tubers that have become green, which tend to be ones closer to the surface during storage and have accumulated more day degrees.

“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 3C slows the process.”

Early-lifted potatoes going into storage could also be at higher risk, says Simon Alexander, an independent agronomist based in Norfolk.

“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 for those lifted into ambient stores, as in the earlier part of the season we weren’t getting cooler nights, which will exacerbate the risk.”

Maleic hydrazide uptake

The unknown factor is how well maleic hydrazide applications were taken up during the season, with good uptake helping to delay dormancy break. In contrast, poor uptake would 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 – it was dry last year and we saw some quite good uptake,” says Simon Alexander.

Simon Faulkner, too, has not seen any results of maleic hydrazide uptake, although he 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,” he says.

There appears to be less concern over crops that appear to be sprouting in the field, according to Simon Alexander.

“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.”

Monitor, monitor, monitor is the advice from both agronomists.

“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.”

Storage applications

Orange oil is one option for controlling sprouting © UPL

Considering the potential for dormancy to break earlier than usual, Geoff Hailstone, potato technical specialist for UPL, 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.

“Growers have multiple in-store sprout suppressant products to choose from, with each having notable benefits.

“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.”

He says the the market is tough at the moment, and every little gain helps improve profitability.

“You might end up needing one or two more applications than usual,” notes Simon Faulkner.

“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.

“It’s standard practice in any year, but follow best practice and you get good application efficacy.”