Crop Watch VIDEO: OSR spraying tips

A late flush of blackgrass in wheat crops following a week of heavy rain and mild temperatures needed controlling as a priority, say our Crop Watch agronomists.

Heavy blackgrass populations were emerging and growing away strongly in wheat crops after 20-50mm of rainfall last week, said Iain Richards, of Masstock Arable (Hants/Wilts/Oxon).

Following a highly-variable performance from pre-emergence residual herbicides, he was targeting blackgrass at one to three leaves with full-rate Hatra (mesosulfuron + iodosulfuron).

“Having used flufenacet as the base for our pre-emergences, we are combining it with a pendimethalin-based residual for the best all-round activity,” he said.

“Even if the blackgrass gets beyond three leaves we will keep on spraying to take full advantage of this season’s very active early weed growth and whatever spray days are available.”

With plenty of aphids still around, Mr Richards was including a follow-up aphicide in the mix for early-drilled wheats, while all second wheats were getting Nutri-Phite PGA for its “timely rooting boost”.

In eastern regions, Prime Agriculture’s Marion Self, was focusing on the correct timing of Atlantis (iodosulfuron + mesosulfuron) applications to tackle the sudden flush.

“Applications must be applied when the spray can dry on the leaf before the evening dew settles,” she said. “In marginal conditions, or where resistance could be a problem, good spray techniques are paramount.”

In winter cereals, barley yellow dwarf virus (BYDV) and aphid control should be reviewed field-by-field, she suggested.

“The Rothamsted Aphid bulletin shows active migration of the bird-cherry aphid (a primary BYDV vector) at the end of October. Consider a final insecticide for BYDV control to any unprotected crops during this time.”

High levels of mildew were present in many winter cereals and infection was most severe in stressed crops, such as light land barley, said Ms Self.

“Symptoms are mainly cosmetic and likely to subside in moist, cooler conditions. But vulnerable, struggling crops may benefit from a mildewicide to protect new growth. Low levels of yellow rust are also evident on susceptible wheats.”

After an incredibly dry six months, AICC agronomist Bryce Rham, of Shropshire, reported 25-40mm of rainfall in the past 10 days across the whole region – enough to get all crops chitting. However, the regional soil-moisture deficit remained unaffected.

“The rain arrived too late for some oilseed rape crops,” he said. “About 120-200ha of rape has been ripped up in the area and either replaced with a second or third wheat or winter oats.”

Winter oilseed rape crops were at cotyledon to eight to 10 true leaves, depending on moisture levels since drilling. Cabbage stem flea beetle larvae could be found in some plants and phoma sprays had been applied over the past two weeks in conjunction with a graminicide, he added.

“Several acres of rape are still only at cotyledon to two to three true leaves. We are leaving them to see if they make it through to the spring.”

In stark contrast, AICC agronomist Hamish Coutts, of Perthshire, said crops were recovering from an extremely wet growing season so far. Oilseed rape crops looked well, although slugs had thrived in the monsoon conditions, he said.

However, potato lifting was still proving to be a trial, with self-propelled harvesters being imported from further south to try to salvage potential crop write-offs.

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