Cereal growers and those with re-seeded grassland in the south and west need to watch out for higher than normal numbers of frit fly, Dow AgroSciences has warned.

Frit fly activity last week (w/e 18 Sept) was almost three times higher than normal, according to latest results from the firm’s Pestwatch service, carried out in conjunction with ADAS and the Scottish Agricultural College.

The mean catch across all six sites of 69.3 adult flies was significantly higher than the long term average of 23.6, with the highest catch in Cheshire (164). Sites in Herefordshire (99) and Shropshire (93) also showed increased activity.

The increased activity follows favourable conditions earlier in the summer, but it is thought that susceptible crops (including winter cereals following grass, grass re-seeds and established grassland) may grow too fast for the fly to cause significant damage.

The hot summer could have also increased leatherjacket risk, said Dow’s David Roberts. Crane flies (the adult phase of leatherjackets) are emerging in large numbers, with some reports of up to 20 adults/m² in south Wales and southern 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.”