Recent weather has been conducive to the build up of rust in sugar beet crops and a treatment could be required to protect excellent yield potential.

So far, it has been an ideal season for sugar beet; with most crops established well in the spring and producing healthy, early leaf cover.

Combined with adequate moisture and plenty of sunshine, prospects are good, but recent cool and wet conditions have favoured rust development which threatens the yield-building green leaf area.

See also: Survey shows green benefits of sugar beet

Independent agronomist and sugar beet specialist Pat Turnbull says that it has been about a month since many growers applied their first fungicide to protect against disease and those that have not yet applied a second to crops destined to be lifted in October onwards should do so as soon as possible.

“I have seen rust developing in crops and with a good price on both quota and excess beet, protecting yield will be important this year,” she explains.

Broad-spectrum approach

Although rust is the main threat at present, conditions could change and other diseases such as powdery mildew, ramularia and cercospera could also pose a threat.

With that in mind, Dr Turnbull favours a broad-spectrum product such as Spyrale or Escolta to protect the canopy against all potential problems.

“If growers are looking for a cost-effective treatment only targets rust, a straight cyproconazole product would fit that requirement.

“However, the broad-spectrum approach will give growers the peace of mind that their crops are protected against other disease threats too,” she says.

Actives

  • Escolta: cyproconazole + trifloxystrobin
  • Priori Xtra: azoxystrobin + cyproconazole
  • Spyrale: difenoconazole + fenpropidin

Syngenta technical manager, Simon Roberts, says that the company’s trials near Rougham in Suffolk have shown not only rust infection, but also ramularia, adding to the argument for a broad-spectrum approach.

He says that Spyrale would be a good option where crops are currently clean of disease, but Priori Xtra could also fit the bill if infection was present – with the product containing both a curative azole and a strobilurin.

“We would expect rust to be the predominant threat, but we have also seen powdery mildew outbreaks in the eastern counties, so clearly a broad-spectrum strategy will be key,” says Mr Roberts.

He adds that an increase in crops destined for later or “just-in-time” lifting before delivery to the factory needed their green leaf protected for longer, which enables cleaner lifting and provides frost protection to root crowns going into winter.

Cleaner harvest

Lincolnshire sugar beet grower and contractor, Richard Ivatt, has seen the benefit of improved green leaf area retention by applying a robust fungicide programme.

He says that while British Sugar is pushing for microtopping, which results in less damage to the root crown during the harvesting process, they also want less green material delivered to the factory.

“That is virtually impossible if you have dead, rubbery leaves on the plant that wrap around the scalper knife.

“With a healthy, upright green leaf we can achieve not only higher yields, but also a consistently cleaner top and improved root quality going into the factory,” he says.

Dr Turnbull says that a third spray around four weeks after the second has been applied may also be necessary and some of her clients will be trying the three-spray approach this season.

“However, growers need to be mindful of the harvest intervals of any products they apply though, so should check the label and not apply too close to the lifting date.”