Crop Watch: Blackgrass grows apace but weather halts spraying

Blackgrass control had got off to a bad start in the east, said UAP agronomist Will Foss. “The worst situations are first wheats following oilseed rape where blackgrass control in the rape was incomplete.”

Wet and windy weather meant growers were still waiting to apply Atlantis/Horus (mesosulfuron + iodosulfuron), he added. “At least conditions remain mild with soil temperatures hovering around 9-10C.”

Conditions had been similar in the south west, said Neil Donkin from Countrywide Farmers. “Blackgrass is also a problem in oilseed rape – we only have up until the end of November to use Aramo (tepraloxydim), but we do now have sufficient moisture for Kerb (propyzamide).”

However, he was concerned that dense crops would prevent it from reaching the soil surface. “It may be necessary to wait for frost and some leaf die-back before spraying.”

Very little phoma had been found but a fungicide would be added to herbicide applications, particularly in thicker crops that required growth regulation, he noted. “Mildew can be found in winter barley, but unless it is very backward and on lighter soils it is probably not worth treating.”

Further south mildew was rife on upper barley leaves, said H L Hutchinson’s James Boswell, Kent. He thought an application of a mildewicide would be worthwhile on lighter ground where rooting and drought tolerance could be adversely affected.

But crops were well established and had received a pre-emergence herbicide. “They now need a pyrethroid for barley yellow dwarf virus control tank mixed with a residual top-up based on chlorotoluron (on tolerant varieties).”

Soil temperatures were now low enough and moisture high enough for Kerb (propyzamide) applications to be reliable in winter oilseed rape, he said.

In East Lothian, AICC agronomist Andrew Riddell was also advising growers to push on with propyzamide applications in oilseed rape. “Oilseed rape is an excellent crop in which to tackle brome or blackgrass infestations.”

Where autumn herbicides had not been applied to wheat crops, growers could fall back on products such as Othello (mesosulfuron + iodosulfuron + diflufenican) for larger annual meadowgrass in the spring, he noted. Some early-sown barley was going yellow, particularly on the headlands. “Crops will have used up any available soil nitrogen and where roots have come across unfavourable soil conditions the results are clear to see.”

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