Scholarship winner ready to get scientific
Jonathan Jamieson, a Lincoln University student, has been named as the latest recipient of Ravensdown’s Hugh Williams Memorial Scholarship.
The message is based on the latest research in Europe on managing disease resistance to fungicides.
Dr Andreas Mehl, a world expert in disease resistance in horticulture and arable crops, was in New Zealand recently to communicate the latest research to our researchers, growers and advisers. Mehl is a senior scientist at Bayer's Research Institute for Disease Control, Germany, specialising in investigating disease resistance to fungicides.
"We should not endanger a certain class of fungicides in regard to resistance," Mehl told Rural News.
"We should alternate different fungicide modes of action by mixing products. Sometimes growers stop using a certain group and overuse the other one.
"Over a long term this is not sustainable. To understand this is crucial for NZ and all parts of the world where crops are grown."
He says the message is to keep on using all the tools you have to control all these diseases.
"Do not be too quick to skip a mode of action just because a new mode of action is available and performing better at the moment," he says. "This is human behaviour of course: if something is new you tend to use the new stuff. But if you exclusively use the new stuff there is a risk of resistance developing much quicker."
Mixing an old multi-site product with a new product may slow further development of resistance to the old product and prevent resistance developing to the new product.
"Every decent mode of action can help the other survive longer or as long as possible."
Mehl says his visit to NZ was to bring the latest findings on resistance in key crops such as grapes, apples and cereals – but resistance advice applies to all crops. He was representing Bayer and the international Fungicide Resistance Action Committee (FRAC).
Economically important diseases in NZ that are rated as high risk for resistance development are grey mould and powdery mildew in grapevines, Ramularia leaf spot (barley) and black spot (apples).
Grey mould is among the worst diseases on the planet for grapes, apples and many other crops, says Mehl. The pathogen has been reported by many researchers in Europe and the US as showing multiple resistances to all available fungicidal classes.
"Growers may be confused about how to control the disease. But it has been figured in latest research and control programmes that full alternation of all the mode of action – even if they previously have been described as causing resistance – still provides sufficient control.
"In a laboratory you test only a single component in a single test system and researchers then publish something about resistance," he says.
"In the field it is different: the plant gives a defence towards a pathogen. Strains reported to be resistant in the lab are still controlled in the field if the products are used in the right way."
There are different disease control and resistance management strategies depending on the crop and the most relevant pathogen(s). Bayer studies at least 40-50 different systems in regard to pathogens and fungicide groups. Increasingly results show that tools involving mixing products are generally applicable.
"So mixtures and alternation are becoming more and more relevant. In the past it was mostly convenient for the grower just to buy a product with a single fungicidal component inside and it was convenient to buy one big package and use it all season."
He says university research based on laboratory science is valuable scientific information but is not automatically transferable to the practice.
"If somebody in the world writes a paper about detection of resistance it does not necessarily mean that a farmer should directly stop using it just because somebody reported about resistance.
"This needs to be clarified because some farmers just tend to stop using a product because they heard about appearance of resistance and then interpreted the findings to stop using the product."
Bayer does considerable field work and tests different spray schedules for all sorts of crops. "Firstly we do this to improve and optimise field efficacy but also to develop sound resistance management strategies.
"We develop a lot of spray programmes for farmers; we are convinced the spray programmes are sound and designed to get high yields. At the same time resistance is taken into account."
Farmers should discuss spray programmes with advisers or manufacturers.
"Communication is the key to optimise spray programmes in both directions – the direction to good disease control, high yield and quality of the produce, and on the other hand to prevent resistance development as much as possible.
"We give the information out to the adviser and the officials and they have the chance to transfer this information to the grower.
"We need to learn from the grower and the advisers but our objective is also to inform them about our findings because we are all in one boat.
"If we develop a product which is not useful to the farmer then it is a waste of money. If the farmer uses a product which is not working any more he is losing money and we are all interested, of course, in a good yield and harvest. The key is communication."
