South: Cereal herbicides and oilseed rape a priority

Over the last seven days we have had a phenomenal amount of rain. Last week Tuesday there was 3.5cm leaving the heavier ground impassable.

On the plus side all the crops are now evenly emerged and making rapid growth in the mild weather. Slug numbers are diminishing on the treated fields. However, where no treatment has been carried out there are signs of severe grazing and these fields should be carefully monitored. Under the present wet conditions I find that pellets bases on methiocarb such as Rivet give the best control.

Winter wheat crops are at the two to three leaf stage and clean. Winter barley crops are at the three to four leaf stage and have signs of Net blotch and Rhynchosporium, particularly on varieties Flagon and Casatta.

The problem is particularly worse on the min tilled fields where the infection has been picked from the trash in the field. Usually it is not economic to spray barley in the autumn against disease as the cold frosty weather would normally control the diseases, but in the absence of frosts at present watch the disease progress.

The mild weather with no frosts so far means the crops are fairly soft. Don't use any complicated herbicide tank mixes, especially those containing insecticides for fear of crop scorch. Some slight scorch is already evident, even where fairly simple mixes have been used.

Remember that barley is more easily damaged than wheat and that some fields are carrying foliar disease. Where blackgrass has emerged and is at two to three leaf stage then Atlantis (mesosulfuron + iodosulfuron) should be planned in winter wheat. This is particularly important where no residual herbicide has been used.

Oilseed rape crops are growing very quickly and the biggest plants have eight to 10 leaves. Untreated crops are now showing symptoms of Phoma and it would be pertinent to consider an application of a fungicide.

As the crops are well advanced with GAI of nearly three it is worth considering a plant growth regulator fungicide based on metconazole or tebuconazole. The fungicides can be tank-mixed with aphicides to control turnip yellow virus as the seed dressings will be running out of steam in larger plants.

Look out for blackgrass in oilseed rape crops where the graminicides or earlier residuals may not have worked. Consider using Precis (propyzamide) once temperatures have dropped.