VIDEO: Crop Watch – Debate on herbicide timings for oilseed rape
Whether to go on now with carbetamide and propyzamide applications or wait until the soil temperature falls is one issue being debated by our Crop Watch agronomists this week.
AICC agronomist Bryce Rham, Shropshire, said soil temperatures were still too high for carbetamide/propyzamide, which will be applied to most oilseed rape crops to keep on top of bromes and ryegrass.
Phoma has appeared on the earliest drilled oilseed rape crops. Around 70% of the crop has now been sprayed, with very forward crops having growth regulators in the mix.
He said winter barley crops in his area were growing rapidly and the most forward barley was at GS22, but crop scorch was evident on most. “One crop of Marris Otter showed signs of rhynchosporium and downy mildew, so we will be applying a fungicide this week,” he added.
Nearly all the winter wheat has been sprayed either pre-or peri-emergence, he said. Slug activity has been minimal with no treatment required on any second wheats and just a few problematic fields following winter oilseed rape.
Atlantis (mesosulfuron + iodosulfuron) will be applied this week to the few acres with blackgrass and some fields will be treated for brome later this autumn.
But in the north, AICC Yorkshire agronomist Patrick Stephenson said he had started to apply Atlantis, propyzamide, and carbetamide – despite the advice from the manufacturers to wait for cooler temperatures and complete germination.
“Unfortunately, when I see a carpet of grass weeds on fields I fear leaving them is worse than waiting for the email telling me the temperature is right,” he explained.
For Nick Brown of ProCam in Oxfordshire and Hertfordshire, only 25% of earlier drilled wheat crops had enough blackgrass to warrant an autumn application of Atlantis or Horus in the next fortnight.
“It’s unlikely emerging crops will get a follow-up treatment for blackgrass this autumn,” he said.
“In most cases, the large flushes of blackgrass taken out before drilling, combined with good seed-beds and moist conditions, have ensured that most pre-emergence applications are doing a good job.”
Oilseed rape crops have all had a phoma spray and any follow-up sprays were two weeks away.
Most earlier applications of Aramo (tepraloxydim) had worked well on the blackgrass, showing that target site resistance was not as bad as first feared, he added.
However, a second flush of blackgrass was appearing in some oilseed rape crops and Kerb (propyzamide) will be used later this month once soil temperatures have dropped below 10C.
In Suffolk, Brian Ross of Frontier Agriculture said soil temperatures were still too high for the most efficient use of propyzamide.
However, with reports of some fop/dim chemistry failing and large blackgrass areas, carbetamide treatments had gone on earlier than normal with a follow-up spray scheduled once soil temperatures drop.
