Yellow rust and Septoria may be the talkingpoints for most specialists as far as this seasons wheat is concerned, butAgrii head of agronomy, Colin Lloyd warns that the biggest potential threat facingmany crops is brown rust.
Conditions so far this season areremarkably similar to 2006/7, he insisted at the Bishop Burton conference.Back then we had just two frosts of below -5oC, lush crops from anopen autumn and early winter, large areas of rust susceptible cultivars and newrust races expanding their host range.
Many growers didnt apply a T0, brought their T1s forward to counter an earlyseptoria threat and opened the door to a brown rust epidemic by leaving toomuch 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 diseasein early 2011, Colin Lloyd recalled. But, thankfully, seven hard frosts inFebruary averted the threat.
So far this season weve only recorded six frosts and none of them have beenbelow the -5oC necessary to reduce brown rust inoculum by causingsignificant lower leaf loss. Nor is there much, if any, prospect of asignificant cold snap on the immediate horizon. And over 40% of the wheat areais 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 inearly-sown wheat at Agriis trial on the Scottish borders and Colin Lloydstimely warning couldnt be clearer.
In response, he urges growers and theiragronomists to check susceptible varieties, in particular, very closely forbrown 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 vitalto knock any infections on the head early, he advised. We know from 2007 justhow rapidly and aggressively brown rust can cycle if it isnt tackled at thestart of the season, how difficult it is to control once it gets going and howdamaging it can be to yields.
Crop prices certainly dont look tooencouraging at the moment. But most wheat is well-established and full ofpromise. So maximising yield has to bethe key priority. Which means the very last thing anyone can afford is anotherbrown rust year like 2007.