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Crop Advice & Expertise

What’s happening in fields across Cambrigeshire and Essex in November?

Tackling blackgrass in oilseed rape and cereals is discussed by Sam Harvey this month and he also warns of a potential aphid threat which may require treatment

At a Glance

This month’s update includes information on:

  • Protected oilseed rape against light leaf spot and TuYV
  • Contact herbicide applications for blackgrass and ryegrass control
  • Mildew levels in winter barley
  • Aphid and barley yellow dwarf virus (BYDV) risk in cereals

Oilseed rape

A warm October has seen oilseed rape crops put on plenty of growth. Any broad-spectrum fungicide applied for early phoma infection will soon start to run out of steam. Those yet to receive a fungicide or one with light leaf spot activity would benefit from some Proline (prothioconazole) as soon as the sprayer is passing through the crop.

Despite the Rothamsted light leaf spot forecast predicting relatively lower levels for the East than in recent years, we know how damaging the disease can be and how important it is to apply fungicides protectantly. The disease is typically asymptomatic this time of year, so incubating leaves will identify any latent infection present.

To date the relatively dry and warm soils of circa 12C means optimum propyzamide application conditions haven’t arrived yet. However, recent days have seen air temperatures start to drop and it's always a balance between getting the persistency from the herbicide and ensuring blackgrass hasn't rooted beyond the active zone. Where using a propyzamide plus aminoypyralid product, the decision is simpler. 

The warm conditions have led to a buildup in Myzus persicae if no insecticide was applied early on. Although crops are relatively large and the potential yield impact of turnip yellows virus (TuYV) less, it can't be ignored that around three quarters of Myzus are carrying the virus this season. If treatment is required, it will be important to keep water rates up for good canopy penetration when using the likes of Biscaya. A tank mix of Proline, Kerb or Astrokerb and Biscaya is a supported tank mix.

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Cereals

It's a tradeoff of risk and reward, but in a number of cases wheat drilling typically started 7-10 days earlier than the benchmark of mid-October. Holding nerve is always testing, but those who continued to hold towards late October will reap the benefits in high pressure blackgrass situations. Soil moisture was sufficient early on for good residual activity but warm soils meant rapid emergence. Moisture became more limiting as the month of October evolved but reducing soil temperatures will benefit residual efficacy.

Where blackgrass and ryegrass has now emerged beyond residual layers and is at 2-3 leaf, some contact activity will be required and Hamlet consistently gives 10% more control than WG formations of mesosulfuron at this early timing. In addition, early applications of mesosulfuron products in close sequence with flufenacet see improvements in control of more resistant populations by around 30%.

Tank mix Hamlet with a suitable residual partner and remember that application conditions are critical. So far, however, in the first couple of days of November, we've had two conducive days, but remember that two tank loads a day is probably the limit.

Warm winters followed by wet summers always result in high aphid pressure. The soggy summer left a green bridge and this is especially so in second cereals where bird cherry aphid numbers are high. Recent mild weather means critical T-Sums will soon be reached for Deter-treated crops, depending on drilling date, and follow up pyrethroids required.

Sugar beet

The warm conditions conducive to beet growth, combined with the pressure seen this season from rust and cercospora, meant a two-spray fungicide application was well and truly justified with early beet yields and sugars good.

Wheat