28 May 1999

Pest control too late

GRASSLAND managers are failing to recognise the need to control leatherjackets or frit-fly and leave it too late to control them.

Bob Clements of IGER, North Wyke, said grassland pests can reduce yield and make fertiliser use less efficient.

"Only 10 leatherjackets as sq ft are enough to cause problems. When birds are feeding in a field it is a good sign that some larvae such as leatherjackets are present."

Leatherjacket populations vary from year to year, and field to field, but there is usually an outbreak every few years, he said. The best way to check for numbers is to use a test kit which many merchants can make available to producers. This involves placing a tube on the soil and filling it with saline solution – leatherjackets come up into the liquid within a few minutes and can be counted.

The other major grassland pest is frit-fly, which occurs in newly sown swards. While this cannot be sampled for in the field, there is a checklist you can use to assess risks. One key factor is the sowing date. Grass sown in mid-August is at severe risk of frit-fly damage, he warned. &#42