Recent reports of adult crane-flies in Central England and Northern Ireland mean growers need to be alert for damage. Earlier this spring the SRUC reported numbers in the soil at the highest recorded levels in 39 years.
Adult crane-flies lay eggs July-September particularly on grassland or in “grassy” stubbles. Hatched leatherjackets are vulnerable to desiccation especially when young, however the rainfall forecast next week may aid their survival. Growers should be alert for any damage particularly on newly established cereals and grass leys.
Leatherjacket Damage Thresholds
|>0.3-0.5 million/ha (30-50/m2)||Damage likely in new ley or cereal|
|>0.5-0.6 million/ha (50-60/m2)||Autumn population in grassland likely to cause damage in following cereals.|
|>1 million/ha (100/m2)||Population in permanent grass where treatment likely to give economic benefit.|
|>2 million/ha (200/m2)||Population in permanent grass likely to show visible damage if untreated.|
Fields with a history of leatherjacket damage should be monitored for large numbers of rooks and crows feeding on the larvae. Risk assessments and testing for the presence of leatherjacket larvae will provide a good indication of fields that are most likely to need treatment.
For cereals applications may be made from post-drilling.
Find out more about controlling leatherjackets in grassland and cereals.
If treatment is justified use Equity® at 1.5 L/ha applied in 200 to 1000 litres of water/ha.
If using Dursban® WG at the recommended rate is 1.0 Kg/ha applied in 200 to 1000 litres of water/ha.
Be aware control will be reduced if soil temperatures are below 5°C or soils are dry as the larvae will move deeper into the soil profile.
Use low drift nozzles and extend buffer zones to preserve Dursban WG and Equity use.
For conventional boom sprayer:
- Use LERAP – low drift – three star nozzles
- AND adopt a 20 metre no-spray buffer zone (1 metre for dry water bodies)