Growers are being advised to be vigilant this season ahead of ear sprays, despite Fera monitoring only recording low levels of Fusarium pathogens so far.
The Met Office mid-range forecast until June 11th predicts drier conditions for northern areas but humid and showery conditions for southern parts from the start of June and continuing the week after.
Although the risk is higher for southern areas it is a localised disease. In 2016 there was little in the way of stem-based browning during the spring yet over 80% of all final Fera samples had Fusarium symptoms.
Fera’s Phil Jennings notes that infection only requires high humidity for 24-48 hours, such as heavy showers over a couple of days. “It is the weather at flowering that ultimately determines the severity of Fusarium infection. In 2016 a number of areas were hit by humid, showery conditions as crops started to flower.
“Our samples that season revealed Microdochium as the most common species, with 69% of samples having the disease. We also recorded Fusarium poae and Fusarium graminearum too. But it was localised. We saw completely different results from sites which were in reasonable proximity to each other – it was all about where the showers occurred.”
It is weather worries that concern Bayer’s Tim Nicholson. He notes that it has been a protracted T2 for some and is concerned that growers might hold off T3 sprays. “Early to mid-anthesis is the best time to protect against Fusarium, but the window is short. Sprays applied after this period will probably result in control being compromised. I can understand why working to a calendar date from GS39 might appear appealing, but you are then reliant on dry weather to help hold Fusarium, and foliar pressure.”
He says Microdochium cannot be discounted following dry weather in April and early May but another aspect of that changeable weather which delayed some T2 sprays is the impact on Fusarium graminearum. “Showery conditions in May are favourable to the development of Fusarium graminearum perithecia, which can lead to a peak in sporulation of these fruiting bodies as we approach flowering. The storms on the run up and during the bank holiday weekend will have heightened inoculum for crops soon to flower and increased the risk that a toxin threat could still develop.
“With Microdochium already recorded at some sites when Fusarium monitoring commenced in late April we could again see more than one Fusarium species threaten. Proline275 (prothioconazole) is the logical choice for T3 sprays with it being effective against the entire Fusarium ear blight complex,” he concludes.