Initial trials suggest the new carboxamide fungicides, if approved, will play an important role in future wheat fungicide programmes, Keith Norman, Velcourt‘s technical director says.

But pricing will need to be carefully assessed by manufacturers, he warns. “The price premium will have to be seriously looked at, especially with commodities under pressure. There is a lot of wheat being produced in the world, which is not going to help prices.”

The first new carboxamide, Bontima (isopyrazam + cyprodinil) has a significant price premium, he believes. “It is not going to be a big product on farm for us this year as its approval was too late to factor into our plans, although we are encouraging our farm managers to try some.”

In Velcourt trials Bontima has yielded similarly to barley fungicide standard Fandango (fluoxastrobin + prothioconazole) in Optic spring barley where rhynchosporium was the main disease.

The chemistry also has much to offer in wheat, he believes. Trials mixing a triazole fungicide with either isopyrazam, penthiopyrad from Du Pont or Bayer CropScience’s bixafen + prothioconazole mix gave around 0.4-0.7t/ha higher yields last year.

Velcourt has been looking at the new chemistry hoping to use it to the best effect once maximum residual levels have been set in Europe for the two actives, and final approval is given.

One key question for both growers and the manufacturers is how does the new chemistry fit with strobilurin use, Mr Norman says.

The carboxamides, or SDHIs, work in a very similar way to strobilurins, by knocking out the energy system the fungus relies on to grow and proliferate. The difference between the two is that carboxamides knock out stage two of the five steps in the process, while strobilurins act on stage three.

“So the big question is: Are these new fungicides a substitute for strobilurins, or can they work together?” asks Mr Norman. “My feeling is there is a place for both. For example, some strobilurins give some control of take-all, while no carboxamide has activity yet. Nor have I yet seen a carboxamide to rival the rust activity of pyraclostrobin. They are all good against rust, but not taking us to a new level of control.”

Velcourt trials this year should provide much more information though, comparing a triazole alone with the same triazole plus strobilurin or carboxamide or both. “We’re looking to see whether there is a cumulative benefit.”

With a similar single site mode of action the other big question is whether resistance will develop to the new chemistry. “Alarms bells do ring because of the single site, and resistance came very quickly in strobilurins, so they should only be used in combination with triazole fungicides to try to avoid resistance build up and to prolong the life of both.”

The triazole will be helping with eradication, while the carboxamide will give protection and longevity. With that in mind, Mr Norman says growers will need to mix a triazole with similar movement characteristics and speed to the carboxamide, so the disease is equally suppressed by both actives.

“So we need more information from the manufacturers about how the actives move in the plant to get that correct match.”

What dose of triazole should be used is also likely to be hotly debated, with some growers sure to be tempted to cut doses on the basis of the activity from the new fungicides. “I wouldn’t use less than a half dose of triazole with them, but I don’t think we will need a three-quarter dose as you do when using alone.”

Management changes needed to deal with food production challenges

Farmers will need to become better business managers and crop technicians to meet the challenge of increasing food production, Mr Norman says.

One of the other demonstrations at Velcourt’s Cereals 2010 is focusing on how production has changed from 25 years ago, and what will need to change in the next 25 years to meet the need for increased production.

“We’re not going to be able to magic land out of nowhere to increase food supply; we have a finite resource, so we need to produce optimum yields from that resource.”

The demonstration at Cereals will show how wheat production has increased from 25 years ago, but also how many more sacks of wheat will need to be produced from that same demonstration area to sustain food supply in the next 25 yrs.

“It will also show how other things have changed – for example, oil prices, fertiliser costs and agchem inputs. We will also highlight management changes, such as use of wider machinery, horse power and labour requirements.

“The overriding message is we need to be better business managers and crop production specialists to meet the challenge.”

Finding the missing link between the theoretical yield of 17t/ha and current yields is the Holy Grail. “Weather obviously plays a huge role in yield variation,” Mr Norman acknowledges.

“First wheat yields at our Vine Farm in Cambridgeshire over the past 16 years show massive swings. For example, in 1999 the average yield was 11t/ha, while in 2000 it was just 8.6t/ha. Both crops were managed for optimum yields, so the weather had the main effect.”

Overcoming the weather’s dominant influence on yields will not be easy, he admits. “In April you have to look at a crop’s potential and then manage it to take into account risk for a normal year.”

Velcourt is also investigating what role sunlight has on yields. “We think it is a key driver for yields. We’re looking at weather trends to see if there is anything in terms of sunlight accumulation we can use to predict likely response to the inputs we are going to make to crops. We are all very good at measuring rainfall and temperature, but this key input has never had the attention it deserves.”