Frit fly and leatherjacket alert following hot summer

UK - September 22, 2006

Newly-sown winter cereals and grass re-seeds following grassland may be at higher risk of Frit fly and leatherjacket damage after the hot summer. 

Crane flies, the adult phase of leatherjackets, are emerging in very large numbers from grassland across the UK.  Reports are coming into Dow AgroSciences’ PestWatch service of up to 20 adults/m² in south Wales and the south of England. 

“Adult crane flies quickly lay their eggs in grassland or arable fields with grassy stubbles with leatherjackets emerging two weeks later.  If the top layers of soil remain moist over the next few weeks, then a very high egg and larval population survival is expected this autumn,” says Dow AgroSciences’ technical services leader David Roberts. 

This summer’s weather has also provided ideal conditions for Frit fly development. Dow’s PestWatch reports that Frit fly activity has been slightly higher and more prolonged than last year, although recent wet conditions may mean susceptible crops may grow too fast for the Frit fly to cause any significant damage.” 

Susceptible crops include winter cereals following grass, grass re-seeds and established grassland. Frit fly larvae bore into the centre shoot causing tiller loss, stunting and sometimes plant death.  Infestations result in poorly-established, patchy crops that may need re-drilling. 

A high population of grass leys may need patching up, or even reseeding, as a result of the recent drought and exceptionally high temperatures.  So a considerably higher area of grassland than usual will be at risk from early leatherjackets and Frit fly this autumn. 

Mr Roberts advises growers to check susceptible crops to be on the safe side.  “The best course of action is to use risk assessment charts.  If a significant risk is identified apply Dursban WG (chlorpyrifos) at 1.0 kg/ha. If an integrated pest management system is in place for Frit fly control, reduce the rate to 0.45 kg/ha,” says Mr Roberts.