Friday, 24 August 2018 12:55

NZ cereal growers can learn from overseas experience – report

Written by  Nigel Malthus
Adama’s visiting English expert on cereal fungicides Andy Bailey. SUPPLIED Adama’s visiting English expert on cereal fungicides Andy Bailey. SUPPLIED

It is time for New Zealand cereal growers to adopt multi-site fungicides (MSF) to combat growing resistance to the more traditional chemistries, says Adama UK fungicide expert Andy Bailey.

While MSFs such as folpet have been used for many years to combat downy mildew in grapevines, they have not generally been used in cereals.

But Bailey says NZ growers have the opportunity to adopt MSFs now, to head off increasing resistance to the more commonly used azoles and SDHI fungicides.

Adama NZ recently brought Bailey here for a week of meetings with agronomists and others.

Septoria was the major disease of wheat in UK and Ireland and it was becoming an issue here, he says. The effectiveness of azole fungicides gradually eroded from about 90% pre-2005 to 30-40% currently.

Now, growers in the UK and Ireland are also starting to see a sensitivity shift in the newer SDHI fungicides.

“We’ve got an emerging situation. We don’t know how long it will be before they start to lose performance in the field. 

“We’ve seen the sensitivity shift and we are seeing some issues in the field,” Bailey explains.

“So alarm bells are flashing and I’ve come here to kind-of say, ‘this is the situation we’re in and this is what we’re trying to do to slow things down’.”

Bailey says it’s an early warning for NZ growers.

“You’ve got a great opportunity now to do things along the lines of what we’re doing in the UK and Ireland and that means embracing things like multi-site chemistry and programmes to protect these other single-site chemistries like azoles and SDHIs.”

He says azoles and SDHIs provide curative and protectant actions but act at only one site in the fungus, which means the fungus can readily mutate to develop resistance.

As the name suggests, MSFs work at several sites in the fungus, which makes it much harder for the fungus to develop resistance. 

Bailey says that makes a MSF extremely valuable in fungicide management because it will keep its performance for many years while protecting the other fungicides from over-exposure.

However, MSFs have only a protectant function, which means they need to be used pre-infection.

“I would say the most effective place to use it here in wheat for Septoria control would be at T1,” Bailey adds.

Farmers must also think about using mixtures in resistance management so Bailey recommends partnering a MSF with perhaps an azole at T1, while saving an SDHI for the T2 application.

Adama is promoting its Phoenix product – a folpet-based MSF – and Bolide, a single-site azole mixture. Phoenix is now in its third year while Bolide is entering its second season.

Bailey says Bolide is an extremely effective mixture of two azoles, which selects for different strains of Septoria.

Meanwhile, Bailey says Ramularia is a major issue for barley. Approval of Phoenix and Bolide label claims for Ramularia in barley are expected soon.


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