Crop Watch: Sugar beet herbicide decisions

James Andrews 11 May 2010

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Weed control in sugar beet and potatoes is top of the agenda for some of our Crop Watch agronomists with others concentrating on T2 barley fungicides and growth regulator application.

Earlier-drilled sugar beet was growing well in Cambridgeshire and final broadleaved weed herbicide decisions were being made, said UAP agronomist Will Foss. “Dry conditions have caused variable emergence of later-drilled crops, particularly on heavier land. Reverting to safer herbicide mixtures has been necessary in some cases.”

Disease pressure in wheat had been relatively low, although there had been reports of yellow rust, mainly on Oakley and Viscount, he said. “These have tended to occur where a T0 was not applied or was applied late.”

In Scotland, weed control in potato crops had been average, but increasing soil temperatures and moisture content could boost residual activity, said SAC’s Mike Inglis. “The main concern for later-planted crops is the effect dry ridges will have on residual herbicide efficacy.”

An increase in the number of contact herbicides available would help clean up emerged weeds, but dry conditions meant residual products would still be important, he said.

Early-planted winter barley was coming into ear in Gloucestershire, often with the crop no more than 12in tall, said Neil Donkin from Countrywide Farmers. “T2 fungicides have been applied in the past week and disease levels are low. Some crops are looking very open as a result of a dry April and yield potential must have been reduced.”

Atlantis (mesosulfuron + iodosulfuron) efficacy in wheat was causing concern, he said. “Conditions since application have been far from ideal and I am concerned that some blackgrass is recovering.”

In Kent, HL Hutchinson agronomist James Boswell said T0 fungicides in wheat had worked well and there was no sign of yellow rust pustules prior to T1 applications. “Septoria tritici remains only on the lower leaves, but pressure is increasing since the heavy rainfall – it has been too cold for brown rust.”

Wheat development was variable with crops ranging from flag leaf just emerging to first node, he said. “T1 applications have been delayed on backward stands due to last week’s windy conditions.”

Growth regulation had been difficult where crops were stressed due to dry conditions, he added. “But assessment is now recommended to see if a later growth regulator is needed on stronger crops – these will need to be applied before GS37.”

Some early-sown spring barley in East Lothian was hit with rain and snow at the end of March, said AICC agronomist Andrew Riddell. “Spring barley likes to get off to a quick start, and the opposite has happened this season – there are many good fields, but others are showing typical May yellowing which greatly affects tiller survival.”

Later-drilled wheat had final leaf three appearing and crops were being treated with a T1 fungicide, he said. “With more wheat following white crops this season don’t forget to check for eyespot.”

Septoria levels were low to moderate in susceptible varieties and yellow rust had been kept out by the T0 spray, he added. “Mildew as ever is very much site specific, but generally at lower levels this season.”