Fusarium control might take on a greater importance for northern growers targeting wheat at bioethanol markets, believes Jim Rennie, technical director of CSC Cropcare.

Mycotoxins can significantly lower the feed value of distillers grains, a core component of the financial viability of bioethanol plants, along with the biofuel and carbon dioxide, he explains.

“It has been explained to me that, at the worst level, mycotoxins can ruin the feed value. And if you look at the advice for the pig and poultry industry, for example, it is not to use feed containing mycotoxins.”

Another concern for bioethanol processing is research that suggests fusarium, microdochium and cladosporium infections could have a negative effect on enzymes used to convert starch into alcohol, potentially reducing alcohol yields or the plant’s efficiency.

Historically mycotoxin levels in northern Britain have been low. But slowly increasing areas of maize being grown as far north as the Borders will increase risk, Mr Rennie points out.

“And fusarium levels have increased in the soil and on the seed in the past two years. Hardly any seed lots haven’t had some fusarium or microdochium recorded, so it suggests an increased risk in 2010.”

Ear sprays have the biggest single impact in controlling fusarium, but using fusarium-active fungicides throughout the programme has a benefit, he says.

Prothioconazole is the standout for fusarium activity, but other actives including metconazole, tebuconazole, prochloraz and boscalid can contribute, he notes.

All could feature in fungicide programmes for wheat crops destined for either bioethanol or distilling markets, he suggests. The central aim for both is to maximise alcohol yield, which is dependent on high starch content and low nitrogen.

In Scotland it means more of a balanced fungicide programme, with each timing having an influence, compared with further south where T1 and T2 dominate yield responses. “T1 and T2 give the biggest responses, but the cooler conditions and longer growing season mean T0 and T3, in particular, are relatively more important.”

Septoria is shaping up to be the main foliar disease threat for northern growers this season. Showery rain through most of April has left risk high, Mr Rennie says. “This year could be difficult if we don’t get a four-week period of dry weather, particularly as we are starting from a high infection level.”

Control should be built around epoxiconazole or prothioconazole-based products, he says, although the former is his favourite if rust is also a risk. “80% of wheats for distilling or bioethanol have a rust risk.”

In Scotland yellow rust is more likely than brown rust, but while prothioconazole is reasonable against yellow rust in a preventative situation, Mr Rennie still prefers epoxiconazole-based product in that situation. “There is a gap between infection and when rust bursts out, so how can you be sure you are applying before infection. If I was using it, I would recommend adding a triazole with more curative activity.”

Targeted nitrogen

Nitrogen rates for starch production should be around 40kg/ha below the optimum for milling wheats, Mr Rennie suggests.

“Currently growers tend to put on close to the optimum as there is no premium, and they don’t want to do anything to deter getting tonnage.

“But for bioethanol production the likelihood is nitrogen will need to be more targeted.”

That opens up the possibility of growers applying sub-optimal amounts of N for yield to maximise starch for alcohol, SAC’s Steve Hoad says. “There is a trade-off, and if that happens, there really needs to be a reward for targeting low protein.”

Timing of N is less critical in the north, Mr Rennie notes. “In the south it is important to put larger amounts of N on early, but it doesn’t appear to matter so much in the north. If you use a little more late, it gives a yield benefit, and so is positive on starch. In the south, where it can be drier, then late N can increase grain protein.”

Fungicides are another consideration. Strobilurin and, potentially, the new carboxamide fungicides have been shown to increase yields while maintaining protein levels. That’s good for milling wheat growers looking to boost yields and meet protein targets, but potentially less favourable when targeting low protein.

But Mr Rennie believes using the yield-enhancing properties of the chemistry will still overall be positive for producing distilling and bioethanol wheats.