Weed control in cereals and oilseed rape has been the key focus for our Crop Watch agronomists this week, but some have struggled with hebicide shortages.
In Northumberland, the shortage of flufenacet herbicide products meant they had to be targeted carefully, said David Cairns from McCreath Simpson and Prentice. “We have saved our flufenacet products for fields with a history of brome and blackgrass and will be going with early post-emergence sprays on other fields.”
Pendimethalin, picolinafen, diflufenican, chlortoluron and Lexus (flupyrsulfuron-methyl) would be the main recommendations and he would be mixing and matching these according to weed targets, variety tolerance and timing.
Slug pressure was low, mainly due to cultural controls, so pelleting had been minimal, he said. “Hopefully, this will reduce metaldehyde spikes in water, but as weather has changed and seed-beds may not be as good we need to be on our guard.”
Pre-emergence herbicides were working well in Devon, but the rapid turnaround between crops meant cereal volunteers could be a problem, said Matford Arable agronomist Neil Potts. These would need to be tackled early to avoid unwanted competition and nitrogen uptake, he added.
Most barley crops would be treated with a pre-emergence herbicide as grassweed control post-ememergence was difficult, he said. “This is particularly important if the variety isn’t chlorotoluron tolerant.”
He was also prioritising flufenacet products, saving them mainly for barley crops. “I’m planning to use a different approach, probably post-ememergence, on the wheats where difficult grassweeds are not such a problem.”
Eastern Crop Watch agronomist Marion Self from Prime Agriculture was monitoring oilseed rape crops in Sufflok for signs of phoma. “As yet, I have seen few phoma lesions, but an early infection is expected following wet conditions during August.”
Growers should continue to monitor crops and treat once a threshold of 10% infected plants had been reached. “Extra vigilance and quick reaction is required on smaller plants as there is less distance for the infection to travel before reaching the stem where it is beyond the control of fungicides.”
Typically, phoma sprays were based on flusilazole, difenoconazole or prothioconazole, she added. “In a season where early phoma infection is likely it would be wise to choose the triazole with most activity. Even varieties with a relatively high stem canker score respond well to treatment.”
Most oilseed rape in Tod Hunnisett’s Sussex area had been sprayed or was about to be sprayed with a gaminicide. “I tend to use tepraloxydim if blackgrass is the prevalent grassweed and propoquizafop for volunteers and increase the rate for brome. I save the cycloxydims for later on in the season,” he said.
“Very rarely can we get away with one graminicide on oilseed rape if it hasn’t been ploughed and the majority of mine have the second one in conjunction with propyzamide or carbetamide.”
John Sarup, senior potato consultant for SAC, said regular digging of crops pre-harvest enabled growers to identify potential problem crops and plan their storage accordingly. “Common scab and raised lenticels are the biggest concerns for me at present as essentially they are wounds through which disease infection can enter.”
If bacterial inoculum was present, in the form of blackleg, wet rots from water logging, blight, or mother tubers, infection could take place, giving considerable problems in-store, he added.
• Have your say on the pre-emergence herbicide shortage in our forum.
VIDEO: Marion Self looks out for slugs and assesses pre-emergence herbicide efficacy in a direct-drilled wheat crop.