Beware leatherjackets on summer droughted grassland

UK - December 04, 2006

Having suffered the summer drought permanent pasture and short-term grassland could be hit again by high leatherjackets populations, warns Dow AgroSciences.

ADAS entomologist David Green says: “Leatherjacket populations were exceptionally high this spring which led to a high emergence of the adult crane fly in the summer.  Rainfall totals were above average in many areas during September and early October and this is likely to have favoured survival of young larvae.” 

“The summer drought reduced high value ryegrass content in many pastures,” says David Roberts, Dow AgroSciences’ technical specialist.  “Some have recovered with the high autumn rainfall and warm soils, but badly thinned fields should be assessed for leatherjackets and frit fly.  The recovering ryegrass will be more susceptible than usual.”

Dow AgroSciences advises growers to check their pastures and leys, including newly-sown and reseeded areas, and if necessary take appropriate action now.  “Yield responses to leatherjacket control in grassland are always considerably higher from autumn rather than spring treatment,” says Mr Roberts.  

“Crops should be sprayed with Dursban WG at 1 kg/ha at the earliest signs of damage, but avoid periods of prolonged frost as the leatherjackets will be less active. Best results are obtained when temperatures are above 5°C as leatherjackets are nearer the soil surface.”