Crops notes May 04

There is little evidence of disease in Greenmounts’ crops of Claire winter wheat. A T0 application of chlorothanoil e.g. Bravo along with chlormequat in the first week of April Growth Stage 30 has curtailed disease in the early stages of crop growth.

The crop has received its second fungicide (T1) of epoxiconazole e.g. Opus and pyraclostrobin for example Comet this week at Growth Stage 32. This is in line with current FRAG-UK (the Fungicide Resistance Action Group UK) guidelines for 2004 only using strobilurins in mixtures with a triazole and where possible, using them only as protectants and not when the disease is well established.

Spring barley crops (varieties Kirsty and Static) have emerged well. Leatherjackets do not appear to be a problem. Herbicides and fungicides will be applied this month.

Leatherjackets are a risk to newly established spring barley crops. There have been several incidents of leatherjacket damage in grassland, and, more recently, some emerging spring barley crops have been damaged.

Careful monitoring of crops during the vulnerable stages of emergence and early establishment is required to avoid yield loss as mild weather coupled with high leatherjacket populations can decimate a Spring Barley crop in three days.

Crops following grass or grassy stubbles are particularly at risk. Ten 30cm lengths of drill should be examined at random throughout the crop. If ten or more leatherjackets are found from the ten lengths of drill an insecticide treatment containing chlorpyrifos is justified.

Dumps of last season’s potatoes are a major source of blight infection and their management must be incorporated into the potato production cycle.

Potato dumps should be examined regularly for signs of sprout growth and action taken to destroy all green material, which could carry blight infection.

Dumps should be covered with plastic and treated with a residual herbicide e.g. dichlobenil granules. As a residual herbicide, dichlobenil granules need a layer of soil to bind on to. Dumps should therefore be levelled and soil added to cover exposed tubers if necessary prior to application.

Residual granules unlike translocated herbicides such as glyphosate only require one treatment applied before any shoots begin to grow. With translocated herbicides, a green leaf area is required to take up the chemical and that foilage could already be infected with blight.

The granule application rate is 30g/m² costing approximately 11-12pence/m². The granules may cost slightly more than other herbicides, however compared with risk of infecting neighbouring potato crops the costs are insignificant.

DARD Farm Management Notes for May 2004 have been prepared by Greenmount Campus, College of Agriculture, Food and Rural Enterprise - Tel: 028 9442 6771.