Leatherjackets

Description

Leatherjackets are the larvae of Crane flies (Daddy Longlegs). They are soil living larvae with a thick grey-brown skin, no legs and can grow up to 5cm in length.

Life cycle

• Adults lay eggs between July and September in grass and cereals
• Eggs hatch 2-3 weeks later and the larvae feed in mild spells during autumn to late spring, pupating in the soil late May-June
• 90% of the time adults stay and lay eggs near to where they emerge, causing the population to continue to increase in the same field if they are not dealt with

Indicators of Leatherjackets

There are several signs that indicate the presence of leatherjackets:

• Large numbers of adult Crane flies in July and August
• Feeding by rooks, crows and starlings
• Bare patches appearing in the grass

Damage caused

Leatherjackets feed on the roots and stems of grass plants at or below ground level.

New leys

Reseeded leys can be completely destroyed by leatherjackets.

Established grassland

Leatherjacket feeding not only reduces yield, but can also lead to the destruction of large areas of fields. At the economic threshold of 1 million per hectare, the weight of leatherjackets feeding below ground can be greater than the weight of livestock above ground.

Control factors

Ploughing grassland in July and subsequent cultivations can destroy up to 50% of leatherjackets.

Control with Dursban WG

Dursban* WG insecticide gives reliable, consistently high levels of control of leatherjackets. It is acknowledged as the standard treatment. The control achieved is such that dry matter yield can by increased by as much as 80%.

Treatment with 1.0kg/ha of Dursban WG before the first signs of damage could save the crop from months of feeding. This will increase the yield response considerably, as shown below.

Crops identified at risk should be sprayed at the earliest signs of damage. Avoid periods of prolonged frost as pests are less active. Temperatures above 5°C give best results as that is when leatherjackets are near the soil surface.

Spray 1.0kg/ha Dursban WG in 200-1000 litres water.