The UK is known for a variable weather pattern, but since May things have certainly changed! After weeks of cloudy weather and rain, and interrupted play at the start of Wimbledon, most of the country has been treated to days of scorching sunshine. Temperatures have been unremittingly high and many of our lawns as well as our flowering plants have suffered, and more so in those areas where hosepipes are banned. However, don't worry about a brown lawn, because grass is pretty resilient and will always recover after a few showers and mowing will have to start again!
However, lawns may not recover so easily from the ravages of leatherjacket and chafer larvae, which eat away at the roots causing yellowing patches and even death. Foxes, birds and badgers may also dig at the ground looking for these larvae, because they represent a cheap meal, damaging the grass even further. So how do we determine what is repairable damage and what is not?
Chafer larvae are white in colour, with a brown head and three distinct pairs of legs. Pupating during May, they produce flying adults, which lay eggs in June that become larvae in July. These eat away at the grass roots until October, when they over winter deep in the soil.
The larval stage of the daddy-longlegs or crane fly is also problematic. Greyish-brown in colour, legless, and around 5cm in length, they have no obvious head and are rather leathery in appearance. Large numbers of daddy-longlegs appear during late summer. The females lay eggs in the lawn which hatch, releasing larvae that feed on the roots. Less damage occurs during cold weather, because they don't feed much. However, if the weather's mild or as it is now very hot, the larvae continue developing and damage becomes apparent much earlier, during the spring. Infestations are common after a wet autumn, because more of the eggs and larvae survive. If the soil becomes waterlogged, large numbers of leatherjackets may appear.
There is a safe and effective way of controlling these pests by using nematodes, which do not have all the precautions and restrictions associated with chemical controls which would prohibit children and pets to play on areas treated with aggressive chemicals. A biological method of control, nematodes are microscopic worms - the species used are indigenous, so they're completely safe for wildlife, pets and children. The nematodes seek out the larvae and enter via natural body openings. Once inside, they release a bacterium that prevents the pest feeding. The nematodes reproduce inside the pest and release a new generation of juveniles that move out to seek more of the pests to kill. Once the larvae have all been killed, the nematodes die back to their natural levels.
The controls are easy to use. Simply mix the powder with water and dilute as instructed, then water onto the affected areas with a watering can or hose-end sprayer. Soaking the soil thoroughly first and watering regularly for several weeks afterwards will give the best results, because this will ensure that the nematodes penetrate the thatch and get into the soil where the larvae are lurking.
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