Technical
By the end of this year there, will be no chemical methods for the control of chafers and leatherjackets in the UK
keen awareness of the need to adopt solutions that would confer long-term benefits and provide a more cost-effective solution. A recent conversation with the head greenkeeper, Paul Hopkins, confirmed that there have been no further problems - a very positive outcome. Kington Golf Club is the highest 18-hole golf
course in England. The course was designed by the highly regarded golf architect, Major Cecil Key Hutchison. It is regarded as one of the finest natural Links courses in the country. I recently spent some time with the committee at Kington Golf Course, the National Trust, who are the landowners, and their agronomist Chris Roberts. Their approach has been systematic and provides a good example of a golf club working to do the best thing for both their members and the environment. In the past, there has been a need to apply both imidacloprid and chlorpyrifos to strategic areas of the course to control problems with chafer grubs and leatherjackets. They recognise that these pests are likely to become a significant issue in the future and have been exploring the implications of the loss of the pesticides and the use of technologies and controls that can be used going forward.
Cultural control
This constitutes removing thatch (un-degraded plant material) which is the foodstuff of both leatherjackets and chafer grubs. This can be done through a variety of means and each method will result in different volumes being removed over particular timescales: turf stripping will remove all of the organic matter, as will fraise mowing using a Koro Field Top Maker. Less forceful methods would be to increase aeration to encourage the organisms that are already present to degrade the thatch.
Biological control
Two methods can be employed: luring the adults away from key areas using pheromone traps, although this method is generally used as a monitoring tool to establish the size of the population and has a very limited capacity to affect a change on the population. Alternatively, nematodes can be applied to
treat infestations. Nematodes
Nematodes are the most abundant multi- cellular organism on Earth. They are a very diverse group of animals and, although over 25,000 have been described, of which more than half are parasitic, the total number of nematode species has been estimated to be about 1 million. The simplicity of their structure has enabled them to adapt to virtually every habitat on Earth, many species are specialists living in specific ecological niches. A small group of nematode species are
John Handley
parasitic on plants and some of these have gained notoriety within the sports and amenity sectors because of the problem they have caused within turf, and this has been well documented within the Pitchcare magazine. However, the group of nematodes that are
”
used to control chafer grubs and nematodes 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 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. The nematodes feed on the bacteria and host
remains, and each infective juvenile develops into a hermaphroditic female. These females then produce eggs which will develop into both males and females. Only a portion of the eggs are laid outside the female; the remainder hatch inside the female and the juveniles destroy their mother as they develop. These nematodes mature, mate and produce infective juveniles that emerge from the cadaver 12-14 days after infection. When infective juveniles leave the host, they
move around in the soil, searching for a new host to infect. Soil texture, moisture, and temperature all affect dispersal and infection. Heavy soils impair movement, with less dispersal occurring as the percentage of silt and clay increases in the soil. Nematodes are also adversely affected by ultra violet radiation: prolonged exposure to sunlight kills them, therefore, it is important to ensure they are applied in a manner that delivers them away from the surface.
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
- Nematodes can migrate 2-3cm per day, a pack that treats 500m2
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
There are two species of leatherjackets, the larval form of Crane Flies, in the UK that damage turf - Tipula paludosa and Tipula oleracea. The Leatherjackets feed on the roots of the grass, making it more susceptible to disease and killing the plant.
PC JUNE/JULY 2016 I 119 contains 250 million
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