Leatherjacket larvae are the immature stage of the European Marsh Crane Fly. They are tough-skinned, light-grey or greenish-brown with irregular black specks, 3 to 4 cm (1.2 to 1.6 inches) long and live in the soil throughout the fall and winter.
During the day, Leatherjackets feed on grass roots and crowns in the upper 3 cm (1.2 inches) of soil. They emerge to feed on grass leaves and stems at night. If the upper soil dries, these larger larvae migrate to deeper soil. They feed in spring through to early-summer when they form a pupa, emerging in late-summer or early-fall as adult Crane Flies.
The decision to take control measures is better made in the spring because late-summer drought or a severe winter may sufficiently reduce the Leatherjacket population. A well-maintained turf is able to withstand a mild infestation so control measures may not be justified. Higher numbers (greater than 270 larvae/m2) will likely cause turf damage.
- Patches of dead grass.
- Turf begins to thin and die back.
- Improve drainage conditions.
- Avoid irrigating a dry lawn in the fall if you suspect a Leatherjacket infestation.
- Apply an insecticide to the affected area.