21 February 1997

Pre-drill spray advised for Sbarley

SPRING barley growers planning to drill fields at high risk of wheat bulb fly attack should consider applying chlorpyrifos to the soil first.

The warning comes from manufacturer DowElanco, which reckons early drilled crops are vulnerable to the ongoing egg-hatch.

There is no other defence against the pest, due to the lack of approved chemical seed dressings, says the companys Corinne Horne.

Fields following crops which allowed adults to lay eggs in bare soil last summer, such as sugar beet, potatoes, vining peas or set-aside, are most at risk this season, she notes. Many will contain more than the threshold level of 2.5m eggs a hectare.

Egg hatch at the end of last week had reached 2-22% across the country, which suggests it could last until the end of the month. "Larvae can attack crops before they emerge. Growers looking to drill in the next two or three weeks should apply Dursban to the soil, and then incorporate it as they drill," she advises. That will protect crops for at least eight weeks on mineral soils, half that on organic ones, she adds.

Jon Oakley, entomologist at ADAS Bridgets, believes the tactic may help. "The pest can get going as soon as seed chits. It is very difficult to stop, but if you are drilling spring barley in the next couple of weeks this approach could be useful. I would probably put another 10% of seed on, too."

Mr Oakley maintains egg hatch is now slightly ahead of normal, so crops drilled after the end of the month should be safe.

Combat wheat bulb fly by spraying spring barley seed-beds with insecticide then incorporating with the drill, advises DowElanco.