Wet weather watch to counter fusarium fear

All three key species of fusarium ear blight are present in most wheat crops so if the weather turns wet there could be a repeat of last year’s epidemic.

Current dry conditions and an anticipated shorter flowering period point to a low fusarium disease year, but that could change with thunderstorms later this month.

The weather at flowering is vital so growers should be focused on weather forecasts around a likely five-day period of flowering in mid- to late-June.

Phil Jennings, plant pathologist at the Food and Environment Research Agency (FERA), advises growers to be prepared to apply a fungicide spray if rain looks likely.

“It’s all about the weather with ear infections, so growers should watch weather forecasts and take action if rain threatens,” he says.

However, if the dry weather continues then the threat of fusarium will be much reduced while the critical flowering period could be shorter than last year, Dr Jennings adds.

Of the three major pathogens, Fusarium graminearum and culmorum are being seen on most FERA sites, while microdochium is present on crops mainly on lighter and drier soils.

Microdochium was the biggest problem last season, but the other two can cut yield more sharply and also produce harmful mycotoxins.

Dr Jennings says lighter land sites in Norfolk, Lincolnshire and Yorkshire are seeing higher level of microdochium than heavier land sites near Andover and Cirencester.

Jonathan Blake, senior research scientist with adviser ADAS, says fusarium levels are high especially in second wheats around his base at Rosemaund in Herefordshire.

“The risk is higher than in some seasons, but it will all depend on rainfall at flowering during the next week or so,” he says.

“It’s all about the weather with ear infections, so growers should watch weather forecasts and take action if rain threatens.”
Phil Jennings, FERA plant pathologist

Fungicide treatment will reduce the threat, and if growers are unconvinced he suggests they leave a patch untreated to see how the disease can take hold.

Control is advised at the T3 stage of early to mid flowering (GS61-GS65) and the triazole prothioconazole gives the best control of all three species, while other triazoles metconazole and tebuconazole, give good control of graminearum and culmorum.

Triazoles generally give six days of protection and so one spray should be sufficient in a normal five-to-six days flowering period, but if flowering is extended then a follow-up spray may be needed.

East Yorkshire agronomist Chris Coates says he is looking to control fusarium while cutting costs for his growers after a bad harvest last year and poor crop establishment this year.

“At the moment disease pressure isn’t high and there is a feeling that yields will be down, so I’m trying to save for clients where possible while protecting the potential of what’s there,” he says.

He suggests straight tebuconazole at a full rate or mixed with prothioconazole at half to three-quarters rate can be an economic option at T3 while still giving good efficacy.

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