Eyespot could be lurking in the base of crops, growers are warned. The combination of wet weather and cooler temperatures during March and the first part of April couldn’t favour the disease better and it is being found where you wouldn’t usually expect it.
For Crop Management Partners agronomist Tristan Gibbs eyespot is something he rarely sees in the south east corner of the UK. But it can quite easily be found this season, especially in earlier drilled crops. He puts that largely down to the weather but feels variety resistance might be a factor. “Eyespot ratings appear to have fallen away over time. We only have two varieties with better scores than six – KWS Zyatt and Revelation but we have numerous fours, and LG Sundance is less. Perhaps it is a factor.”
He hopes it will dry out now that warm weather is forecast but will factor it into T1 sprays. “I’ve seen the odd bit in the past but usually symptoms disappear as leaf sheaths die off during spring growth. In prothioconazole, boscalid and fluxapyroxad we have enough choice that I can build it into T1 strategies focused on septoria or septoria plus rust. Septoria remains the greater threat in my area but I’m seeing fresh yellow rust in Britannia and autumn drilled Mulika, plus low level brown rust in Crusoe,” he says.
Further around the coast fellow Crop Management Partners agronomist Richard Cromie is also bumping into eyespot, most frequently at fertile sites.
He hasn’t found any signs of penetrating lesions but feels the disease might need dealing with. However he stresses it’s important not to lose sight of priorities. “Only if you get penetrating lesions and severe crop lodging will it cause the same sort of yield reductions as septoria or rusts. This is where the focus needs to be with eyespot control built in, rather than the base for T1 mixtures.”
High septoria pressure will firstly take him down the second generation SDHI route with prothioconazole or epoxiconazole. “The partner triazole can be changed for specific cases – prothioconazole for eyespot or fusarium and wheat after maize, epoxiconazole for brown rust. CTL will be pretty much standard at T1 on all winter wheats,” he notes.
He says eyespot can be difficult to identify – even for an experienced agronomist like him. “Early on, it is difficult to separate from stem-based browning, being more a brown smudge. It’s only when you see the dark brown ringed eye that it confirms the presence of the disease.”
Keep an eye on the T0 to T1 gap
AICC chairman Sean Sparling is seeing plenty of stem-based browning in Lincs and Humberside but in many cases exact diagnosis is still to be determined. “We have noticeably more stem-based browning this season, which could be true eyespot or fusarium.”
It doesn’t surprise him and he sees both diseases most seasons. But this season it is more widespread following such a period of cool, wet weather. He too will base his T1 strategies on septoria or rusts but has a concern with T1 timing. “Now the weather has picked up and crops take up nutrients they could race through the growth stages. I would advise close monitoring of crops as the gap to GS39 could be quite short,” he warns.
He feels plant dissection could be invaluable. “With this warm weather, checking for leaf three emergence by cutting plants open could be worth the trouble. Crops might not look any different a few days from now but could have moved to GS32,” he concludes.
