CONTROLS Nematodes
The group of entomopathogenic nematodes (microscopic worms) that are used to control Chafer Grubs and Leatherjackets are host specific. They are so host specific that different species of nematodes need to be used to control each of the two turf pests. Each of the two nematode species used, Heterorhabditis bacteriophora for Chafer Grubs and Steinernema feltiae for Leatherjackets, can be applied at the same time and won’t disrupt each other. Both of these species are native to Britain, have been used effectively for many years, don’t require any specific personal protective equipment, are persistent in the soil for long-term control and are safe for users and the environment.
The nematodes are natural predators of the two grub species. When purchased, they are produced to be at an infective juvenile stage, maintained in this state by refrigeration. Once applied, they warm up and move through the soil water solution, their objective being to locate and enter a suitable host, either through the skin or orifices. They then release a symbiotic bacteria which kills the host, usually within 24-48 hours.
Key points to understand: • The juveniles are kept refrigerated in a suspended state so that, when they are applied, they warm up and are actively looking for a host; however, they need to be washed off the surface and into the proximity of the larvae. Soil temperatures must be of 12o
C or above. • Nematodes can migrate 2-3 cm per day, a pack that treats 500 m2 contains 250
million nematodes, and these vast numbers artificially raise the natural population to make it an effective control.
• Understanding the lifecycle of the host larvae will ensure that the nematodes are applied when they are most effective.
LEATHER JACKET LIFE CYCLE A
Nematode Application Period DOUBLE RATE
PUPAE JAN FEB MAR APR MAY JUN JUL AUG ADULT EGGS LARVAE 5.
Infective juveniles are produced when resources become limited.
6.
Thousands of infective juveniles released in search of new hosts 12-14 days after infection.
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How Entomopathogenic Nematodes Work in the Soil
3.
Nematodes reproduce for 2-3 generations.
4.
Nematodes become adults in dead larvae.
Leatherjackets
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Chafer Grubs
Infective juveniles enter larvae through natural openings.
1. 2.
Nematodes release symbiotic bacteria Photorhabdus spp. which kill the chafer larvae.
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OCT
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DEC
Leatherjackets B © 2017 Nematode Application Period H Decisions on the precise application period should be taken as part of an integrated pest management plan and be based upon local observations of the pest life cycle. CHAFER GRUB LIFE CYCLE ADULT PUPAE EGGS Nematode Application Period JAN FEB MAR APR MAY JUN JUL AUG SEP OCT © 2017 H NOV DEC LARVAE
There are two species of Crane Fly in the UK that damage turf, Tipula paludosa and Tipula oleracea. The Leatherjackets feed on the roots of the grass plant making them more susceptible to disease and killing the plant. Damage to turf can be seen from September through the autumn, winter and into the spring. The lifecycle of both species means that they can pupate at two times of the year, the vast majority of Crane Flies hatch in August and September, but there is also a small number that pupate in the spring, particularly April and May in recent years. The illustration shows the two lifecycles running concurrently.
Chafer Grubs Decisions on the precise application period should be taken as part of an integrated pest management plan and be based upon local observations of the pest life cycle.
There are six species of Chafer Beetles, the adult form of the Chafer Grub, in the UK. The most familiar being the Cock Chafer or ‘May bug’, a large beetle that can be heard as a low droning noise on pleasant spring evenings. The grubs have stout white bodies curved in a C shape, light brown heads, with three pairs of legs and darker patches at the base of the abdomen. They are bigger than the adult beetles, although their size varies, according to species, between 8-35 mm. The lifecycle of a Chafer Grub is illustrated below and explains that the most effective time to apply nematodes will be between mid-July to mid-October.
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