Multisite fungicides key to slowing cereal disease resistance

The use of multisite fungicides in cereal crops will be vital next spring to slow down disease resistance and help control key diseases such as septoria in wheat and ramularia in barley.

The addition of a multisite into a tank mix has been shown to extend the life of important fungicide groups, such as SDHIs, and so improve overall disease control.

Cereal growers are faced with a dwindling number of multisites, as two of the three in general use face a ban or an uncertain future, leaving folpet as the main option for the future.

See also: Cliff edge of fungicide resistance faced by wheat growers

Of the other two, chlorothalonil is set to be banned from mid-May 2020, while mancozeb is under threat from the regulators. Folpet is about 20% more expensive than the widely used chlorothalonil. All three have been used by growers since the 1960s.

Actives

  • Folpet (Arizona)
  • Chlorothalonil (Bravo plus others)
  • Mancozeb (various products)
  • SDHI fluxapyroxad plus azole epoxiconazole (Adexar)
  • Prothioconazole (Proline)

Resistance risk

These multisites are protective in action rather than curative, but have shown no signs of resistance against diseases such as septoria, while curative or systemic fungicides such as SDHIs, azoles and strobilurins operate on a single site in the disease fungus and do show signs of resistance.

The use of multisites has seen rapid growth in recent years, as they have a low risk of disease resistance and can also protect the single-site fungicides.

Isabel Corkley, research scientist at crop consultant Adas, say these multisites are very important to extend the life of at-risk fungicides such as SDHIs, when used as partner products.

“The use of a multisite, such as folpet, can double the effective life of fungicide programmes,” she told a  recent briefing held by folpet manufacturer Adama.

Her work looked at using the SDHI fluxapyroxad (as used in Adexar) with folpet, but she added that folpet would also increase the life of SDHI/azole mixtures which are commonly used on farm.

Her work with fluxapyroxad concluded that folpet will extend the SDHI’s effective life, the SDHI can be used at a reduced rate, and the higher the folpet dose, the greater the protection given to the SDHI.

She also looked at the azole prothioconazole and showed folpet can contribute to resistance management for this fungicide as well.

Wheat disease control 

David Roberts, technical specialist at Adama, says that the multisite folpet can be used typically at the T1 and T2 fungicide timings in winter wheat, and will give similar septoria control as chlorothalonil.

“Folpet is better than mancozeb at septoria control and comparable with chlorothalonil at a higher rate,” he said. His work was using chlorothalonil at 500g/ha, with folpet at 750g/ha.

He also pointed out that folpet, as in the group’s brand Arizona, gives the same level of control of ramularia in barley as chlorothalonil at the same rates – which will be particularly useful, as chlorothalonil is one the few fungicides to give control of the disease.

“Arizona is as good as chlorothalonil on ramularia and is best used as a two-spray T1 and T2 programme,” he said.

NOVEMBER
3

Ask the... Breeder

Register now

Online grain trading made easy with Farmers Weekly Graindex

It takes just a couple of minutes to create a listing on Farmers Weekly Graindex and you’ll get a range of prices to compare from active buyers who want your grain.
Visit Farmers Weekly Graindex