The Groundsman

January 2016

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TECHNICAL UPDATE 28 the Groundsman January 2016 Visit www.iog.org for more information and digital editions ematodes are a large and diverse group of unsegmented roundworms that include both beneficial and parasitic species. Several species feed exclusively on the content of plant cells and these are referred to collectively as plant parasitic nematodes (PPN). Significant worldwide economic losses due to PPN infections have long been recognised in forestry, agriculture and horticulture, but we are increasingly aware of the potential damage that they can cause to areas of amenity turf. PPN that have the potential to damage turf grasses are microscopic (mostly <1mm long) and feed on (ectoparasites) or inside (endoparasites) the root tissues. Some species live in and feed on cells in the crown or leaf tissues but most of the more commonly encountered species are root feeding. Their small size and lack of any significant colour means that they are virtually impossible to see without a microscope and even then, in order to see them clearly, they have to be separated from the soil or plant tissues. These parasites have a hollow feeding tube (stylet) at their head end that they use to draw food from the plant and also to inject substances into the plant to help maintain their feeding sites. These injected substances can significantly affect the growth and development of the plant and can therefore by definition, directly cause disease. Nematodes have a fairly simple lifecycle. The female lays eggs that eventually develop into juveniles and hatch as infective second-stage juveniles (J2s). The juvenile nematodes N The apparent rise of parasitic nematodes Why is it that nematodes are apparently only now causing problems in cool season amenity turf, or have they always been present but simply overlooked? By: Dr Kate Entwistle undergo four moults (replacing their outer cuticle as they increase in size) before emerging as adult males or females. Reproduction can be either sexual or asexual and species can potentially complete several life cycles per year. Although most individual nematodes are microscopic, the damage they cause to the turf grass plant can often be seen as root swellings (galls) or abnormal root development (root loss, thickening or excessive branching). On the sward, the effect of the damaged root structure tends to show as a chlorosis or wilting of the leaf which results from a reduction in the uptake of nutrients or water. PPN are likely to be naturally present in most, if not all, sports turf rootzones. However, their presence does not automatically mean that damage will develop on the turf, but if their populations build to damaging levels and there is an increase in abiotic stress (ie increased heat, drought or wear stress, low nutrition, reduced mowing height), the sward can rapidly show signs of weakness or become more susceptible to other infections. PPN are basically aquatic organisms and can move over short distances in water films through the rootzone or be transported over longer distances by movement of infected plant or rootzone materials. Negative effect on visual playing quality of turf

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