Nematodes tend to thrive in a sandier rootzone so, our tendency to construct and to topdress with high sand content materials, is further facilitating the development of ideal growing conditions
increase in the frequency and general population size of the Stunt nematode in samples received from across the UK, with some nematode populations over fifteen times the current proposed threshold for damage to amenity turfgrasses. The Stunt nematode is most often identified in the rootzones of fine
matures, her body becomes brown in colour and hardens to form a cyst. Within the cyst, the juveniles develop inside the eggs and, when they have developed sufficiently, the cyst breaks open and the juveniles are released in to the rootzone.
The Lesion nematode is an example of an endo-parasite that migrates through the root tissues whilst feeding on the cell contents. It causes the outer cortical cells of the root to be separated from the inner stele (xylem and phloem) and thereby, renders the root unable to take up water and nutrient from the rootzone. To date, the Lesion
The symptoms on Poa that develop with high Spiral nematode pressure on the roots
nematode has been found on ryegrasses and on close-mown bentgrass swards causing significant decline in turf quality.
The new Gracilacus nematode recently identified in golf course putting greens in Portugal
turfgrass areas rather than soccer pitches but other nematodes, notably the Cyst nematode, Heterodera, can be found in both. The Cyst nematode is another sedentary parasite like the Root-knot nematode, but unlike the Root-knot nematode, the Cyst is a semi- endoparasite in which the maturing female is embedded in the plant tissues but with her body exposed on the outside of the plant. As the female
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Since 2001, when we initially reported that plant parasitic nematodes have the ability to cause disease in cool- season turfgrasses, there has gradual reduction of perceived scepticism towards the idea that the nematodes should be considered as a potential problem in amenity areas. However, over recent years, there has, unfortunately, been an increase in the number of confirmed problems that have been associated with high populations of one or more nematode species.
Is this because nematodes are becoming more of a problem or because we are now aware of their potential and are looking for them in rootzones that are supporting a weak and unresponsive sward? I believe that these nematodes have always been present but our recently acquired knowledge has encouraged us to be more vigilant and to look more closely for them in turf that we may have otherwise reported as
‘stressed’.
It is also true that their populations will be strongly affected by environmental conditions and, that the recent shift towards milder winters and wetter summers, can only encourage the development of their populations. We also know that nematodes tend to thrive in a sandier rootzone and therefore our tendency to construct and to topdress with high sand content materials, is further facilitating the development of ideal growing conditions. Nematodes don’t only cause damage in isolation. High populations can certainly cause disease, as we have seen all too often with the Root-knot nematode. However, for the past couple of years, I have been looking at turf samples that come in to my lab with fungal diseases like Take-all patch, Microdochium patch and Anthracnose, to see if their rootzones also show the presence of plant parasitic nematodes. Quite unsurprisingly, most rootzones do but, more interestingly, what I have seen is a large number of instances where reoccurring fungal disease problems (what I call ‘niggling’ disease developments) are present on the sward above a rootzone containing high nematode populations. There is a lot of research to support the association of fungal disease and plant parasitic nematode activity in agricultural situations but, not surprisingly, none to support this observation in amenity turf. From my experience, I have little doubt that there is a correlation between the two and, if asked to speculate, I would suggest that, in many cases, the nematodes are more likely to cause the initial infection and damage to the roots, initiate a decline in plant strength and adverse changes in plant physiology, which eventually allows the weakened plant tissues to be colonised by fungal disease. It is only then that we recognise a problem in the turf.
So, what do we know?
• We know that plant parasitic nematodes certainly can, and do, cause damage and disease to cool-season turfgrasses. There is much debate still, even amongst researchers, as to what populations are necessary to cause disease but, as I mentioned above, these populations will be affected by turf composition, strength and environmental conditions. There can be no clear-cut answer to this question.
• We know that there is potentially a strong, but currently only theoretical, link between the activity of plant parasitic nematodes and fungal disease. We know this from the
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