Sugar beet growers are to benefit from a new fungicide this autumn for controlling the late season disease cercospora leaf spot, which has worsened in recent years.

This news will be welcomed by growers, given that this is the last season for products containing cyproconazole, such as Escolta (cyproconazole + trifloxystrobin), a key fungicide for managing this disease.

Climate change has seen the fungal disease become economically damaging in British fields over recent years, and while yield losses are typically 25-30%, when combined with other diseases such as beet yellows, can be as high as 80%.

See also: 3 factors growers can influence to maximise sugar beet yields

To help farmers fight the disease without cyproconazole, Bayer has secured approval from the Chemicals Regulation Division of the Health & Safety Executive for the use of Caligula, which contains fluopyram and prothioconazole.

Approval allows for a single application after 1 September at a maximum rate of 1.2 litres/ha, although Bayer’s recommended rate is 1 litre/ha.

However, one condition of the authorisation is that sugar beet tops treated with Caligula must be disposed of and not fed to livestock.

This season

Antonia Walker, Bayer root crop campaign manager, said the authorisation for Caligula will help growers protect yield potential.

“For the 2022 season, the restriction of a single application after 1 September means that for most growers, Caligula will be the third and final spray of the season.

She says that several years of trials show unrivalled protection against cercospora leaf spot, and she believes it will become the default choice for the third spray of the season.

“We are continuing to gather the data needed to support authorisation for two applications per crop,” says Miss Walker.

Resistance

In addition, the discovery in 2016 of cercospora isolates demonstrating reduced sensitivity to strobilurin fungicides at sites in Beccles, Suffolk and Penzance, Cornwall, has underlined the need to respect resistance management guidelines. Miss Walker explains that approval of Caligula offers new actives for managing sugar beet disease, which will help growers reduce the resistance risk.

“Growers should apply no more than two strobilurin-containing fungicides during the season, but independent trials show that if rust and powdery mildew are to be kept at bay, applications should be no more than four weeks apart. The authorisation for Caligula means growers can protect crops against the principal disease threats while keeping the door closed to cercospora,” says Miss Walker.