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Leatherjackets can be damaging in lawns and sometimes kill small plants in flower beds and vegetable plots by eating roots and stem bases. They are often more numerous after a wet autumn, as damp conditions favour survival of eggs and larvae.
Leatherjackets are the soil-dwelling larvae of flies known as crane flies or daddy-longlegs.
How to tell if leatherjackets are a problem in your garden:
A biological control is available for controlling leatherjackets in lawns, flower beds and vegetable plots. This is a pathogenic nematode, Steinernema feltiae, which is watered into the turf or soil. The nematodes enter the bodies of leatherjackets and infect them with a bacterial disease. To be effective, the nematode requires soil that is well drained but moist and with a minimum temperature of 12°C (54°F). The turf around the edge of affected areas should be targeted to deal with larvae spreading out from infestation “hot spots” in the lawn. However, by the time areas of infestation become apparent, the soil may be too cold for nematodes to be effective.
As a preventive measure, apply nematodes in September to early October against leatherjackets. Nematodes should be applied as soon as possible after purchase, following the suppliers’ instructions for use. It may be necessary to water the lawn before and after application to ensure the soil is sufficiently moist for nematode activity and survival.
There are currently no chemical controls for leatherjackets on lawns which can be applied by home gardeners.
Biological control suppliers (Adobe Acrobat pdf)
There several species of leatherjackets (larvae of crane flies) that feed on the roots and stem bases of lawn grasses and other plants. Most species of crane fly are not pests, many feed on decaying organic matter and are important in nutrient recycling.
The adult crane flies or daddy-longlegs mostly emerge and lay eggs in the turf or soil surface from August to October. Dry soil conditions at that time can result in many of the eggs failing to hatch, so large numbers of adult flies does not necessarily mean that there will be large numbers of larvae or leatherjackets in the next year.
The eggs hatch a few weeks after they have been laid and the young leatherjackets begin feeding on plant roots. In cold winters, they overwinter as small larvae and do not grow large enough to cause significant damage until mid-summer. Mild winters allow the young larvae to continue feeding and they can be large enough to cause lawn problems by late winter.
When fully grown, the leatherjackets pupate in the soil. When the adult flies emerge, the pupal case is often partly pulled out of the ground and left sticking up above the lawn surface.
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