February 12, 2014
Watch out for the scourge of brown rust
Yellow rust and Septoria may be the talking points for most specialists as far as this season’s wheat is concerned, but Agrii head of agronomy, Colin Lloyd warns that the biggest potential threat facing many crops is brown rust.
“Conditions so far this season are remarkably similar to 2006/7,” he insisted at the Bishop Burton conference. “Back then we had just two frosts of below -5oC, lush crops from an open autumn and early winter, large areas of rust susceptible cultivars and new rust races expanding their host range.
“Many growers didn’t apply a T0, brought their T1s forward to counter an early septoria threat and opened the door to a brown rust epidemic by leaving too much time for the disease to cycle ahead of T2. As a result, the rust wreaked havoc across the country.
“Conditions were again ripe for the disease in early 2011,” Colin Lloyd recalled. “But, thankfully, seven hard frosts in February averted the threat.
“So far this season we’ve only recorded six frosts and none of them have been below the -5oC necessary to reduce brown rust inoculum by causing significant lower leaf loss. Nor is there much, if any, prospect of a significant cold snap on the immediate horizon. And over 40% of the wheat area is down to varieties with a brown rust resistance score of 5 or less.”
Add to this the fact that, unusually, brown rust has already become apparent in early-sown wheat at Agrii’s trial site on the Scottish borders and Colin Lloyd’s timely warning couldn’t be clearer.
In response, he urges growers and their agronomists to check susceptible varieties, in particular, very closely for brown rust alongside both yellow rust and Septoria in the coming few weeks; especially so if hard frosts continue to be as rare as they had been to date.
“A well-timed and specified T0 will be vital to knock any infections on the head early,” he advised. “We know from 2007 just how rapidly and aggressively brown rust can cycle if it isn’t tackled at the start of the season, how difficult it is to control once it gets going and how damaging it can be to yields.
“Crop prices certainly don’t look too encouraging at the moment. But most wheat is well-established and full of promise. So maximising yield has to be the key priority. Which means the very last thing anyone can afford is another brown rust year like 2007.”