A single year of oilseed rape may not be a sufficient break to adequately safeguard first wheats from take-all, according to the latest trials at Masstock Arable’s SMART Farm in Wellington, Somerset.
Serious patches of whiteheads have become apparent in all six feed wheat varieties in the field-scale trials drilled in late September following oilseed rape after a previous wheat. And root inspections have pinpointed take-all as the primary cause.
“Take-all is a fact of life in many of our second wheats around here,” commented agronomist, Kevin Ashford of Agrownomics responsible for the farm. “So we routinely use the specialist seed treatment, Latitude (silthiofam) to keep it at bay.
“If the current trial had been after set aside we might have been tempted to treat the seed, especially as the land had suffered badly from take-all in the past. But, as a first wheat after rape, we decided not to.
“All varieties established and developed well and, in view of the high residual nitrogen levels from past poultry manure applications, only needed 80 units of N as a liquid in May,” he reported.
“We saw no stunting or other evidence of compromised rooting whatsoever. Until the middle of June, that was, when the hot dry weather started to take its toll and substantial patches of whiteheads developed throughout the crop.
“We found some sharp eyespot on the stems, but no true eyespot; and the lesions certainly weren’t serious. However, when we dug up plants and found the classic blackened roots it became obvious that take-all was the main culprit.”
This evidence reinforces Kevin Ashford’s view that many growers need to have a better cereal break than just a single oilseed rape if they are to avoid the scourge of take-all. Especially if they sow first wheats in September and their cereal volunteer control in OSR is not as good as it could be.
“Don’t think you can safely replace second wheat with rape then go straight back into wheat without taking adequate precautions against take-all,” he stressed. “You may get away with it if you drill your first wheat late enough and have plenty of summer moisture. But if you’ve had take-all problems in the past you really need to take care.
“The first problem is you probably won’t have the time between wheat harvesting and rape sowing to adequately control the cereal volunteers that so effectively carry the disease over. So you’ll have to make sure you do so in the crop.
“At the same time, you may need a two-year break to clear take-all effectively from the soil,” added Kevin Ashford. “Which means specialist seed treatment could well be advisable – for September-sown crops at least.
“The cost of Latitude treatment may be off-putting if you’re drilling at1.5 cwt/acre, but if you drill early with a precision rate in seeds/m2 based on 1000 grain weight you may only need 0.75 cwt/acre so you’ve halved the treatment cost as well as saved on your seed bill.
“If your rape stubble hygiene is not all it could be and you feel you can’t justify the cost of a take-all seed treatment, of course, you’d be better off giving yourself a two-year cereal break by adding peas or beans to the rotation. Or looking to maize or grass if you’re on a mixed farm
“In any event, do also think seriously about stem canker and other oilseed rape diseases if you’re considering the wheat/rape/wheat/rape rotations being advocated by some,” he concluded. “Our experience shows there are serious dangers of compromising OSR as well as cereal performance by tightening rotations too far.”