19 May 1995

Keep doses low to be effective

LOW doses of more effective herbicides and fungicides offer better profit potential than full doses of inferior products according to the latest research funded by the Home-Grown Cereals Authority.

The work carried out by the Scottish Agricultural College included over 60 herbicide and fungicide trials to generate advice for growers in Scotland and Northern England on when low doses are cost-effective and help quantify possible environmental benefits.

The effects of weather, strategic spray timings, tank mixing and sequential treatments were all considered.

In winter cereals sequential low doses were shown to be most reliable for weed control, the best sequence tested giving a 92% success rate.

Control in spring barley was not so simple – the best sequence giving just 55% success. But even the full dose was not always satisfactory, the HGCA notes.

By contrast, the most reliable disease control in spring barley was a low dose sequence of a triazole and morpholine tank mix. That was more cost-effective than two full doses in most cases. However, low doses had to be used very early against mildew, the HGCA comments.

For winter wheat a three-spray, half dose programme proved cost-effective, using prochloraz for early sprays and flutriafol and chlorothalonil later. Morpholine was added if mildew or yellow rust threatened.

Full details of the work are contained in Project Report No 104, Reduced cost approaches to herbicide and fungicide use on cereals in Scotland, priced £5 from the HGCA, Hamlyn House, Highgate Hill, London N19 5PR (0171-263 3391). &#42