If you are in doubt about the best type of sample to send for analysis, telephone the laboratory and ask
Bent nematode or hormone: The symptom of the swollen stem base could be either plant parasitic nematode OR an hormonal response by the plant
Bent nematode or hormone: The symptom of the swollen stem base could be Plant Para Nem: This picture shows patch symptoms on close-m
nematodes.either plant parasitic nematode OR an hormonal response by the plant
A golf hole mown turf caused by plant parasitic
changer takes a suitable sized sample that can be wrapped tightly in dry newspaper
away quickly so symptoms can flare up in a similar way to that of fungal disease. Nematodes cannot be seen with the naked eye but need to be isolated from the rootzone or root tissue and magnified up to 400x or more to allow their identification. With regard to fungal disease, if turf is sampled whilst the disease is active, it is possible to identify the fungal cause of the problem. Many fungi produce spores that are characteristic of a given fungal species and by recognising these, it is possible to confirm the fungus causing the problem. If spores are not present or are not produced, fungal mycelium can help in identification, as too can resting structures and other structures produced by the fungi. Again, many of these structures are microscopic and need to be isolated from the plant or root tissues and magnified 400x or more to allow identification. To identify the presence of a fungal pest or a plant parasitic nematode, representative samples must be received by the laboratory. If you are looking for a potential foliar fungal pathogen and the sample is sent from an area of turf that showed initial symptoms of infection several weeks ago, it is extremely unlikely that the initial cause of the problem will be identified. Damaged and diseased plant tissues undergo a succession of decay and following the initial damage caused by the disease, decomposition of the remaining plant material will take place by other fungi, bacteria and other microscopic organisms. Their presence will mask the signs of the initial disease and they will out-compete the pathogen from the damaged turf. For identification of possible foliar diseases, it is necessary to take a turf sample that is representative of the damage seen and which includes recently infected plants and adjacent unaffected plants. A golf hole changer takes a suitable sized sample that can be wrapped tightly in dry newspaper to prevent the sward from becoming covered with rootzone material. The sample can then be sent by next day delivery to the laboratory for analysis. Small, bulked hollow tine cores are not useful for identification of foliar disease because they tend not to contain many intact plants, have rootzone contaminating the sward and don’t show how the damage is developing on the turf. They can be used to confirm root disease but, with few intact plants found in bulked hollow tine samples, it is often impossible to say which grasses are being affected in a mixed sward. Bulked hollow tine cores are, however, the best way to check for populations of plant parasitic nematodes. Because they are found around or within the roots, bulking small cores from several areas of damage and from apparently healthy areas (two separate samples) will allow a
laboratory to tell you what nematodes populations are present in the healthy turf (background population) and if any one or more nematode populations have increased relative to its background population in the areas of damage. Single hole changer core samples can be used to look for plant parasitic nematodes but the best that they can provide is an indication of likely cause for the damage seen. If you are in doubt about the best type of sample to send for analysis, telephone the laboratory and ask the person who is going to do the analysis. It is important that you receive the most information possible from an analysis but the lab can only work with what they receive.
Symptoms can be different depending on height of cut
The expression to symptoms of disease or invertebrate pest activity, tend to be more acute on close mown turf compared to those seen on the same grasses maintained at a longer height of cut. Microdochium patch, for example, is seen as very distinct patches that tend to show a pale centre and darker border (when active) on close-mown turf and fungal white/pale-pink mycelium may be seen around the edge to the patch. Microdochium patch on less highly maintained turf can appear as tan, slimy turf that is collapsed and decaying. There does not need to be any change in colour of the plants across the damaged area and mycelium does not have to be present. Leaf spot infections can appear more severe on close-mown turf and for many leaf spot diseases, one of the cultural control options available is, wherever possible, to raise the height of cut. Red thread on close-mown turf can appear as patches of red needles interspersed with straw-coloured leaf tissues. On longer turf, the sward can appear generally straw-coloured and the red needles are only apparent on close inspection of the plants.
Checklist for disease
If the problem has appeared in straight lines, look for a potential application problem.
If plants show an unusual growth habit or the turf shows a general discolouration but the new emerging leaf material appears healthy, check recent product applications.
If symptoms appear annually at certain times of the year and follow a specific progression of discolouration or development, look for watersoaking of the leaf, spots, discolouration of the crown / root tissue, or for evidence of fungal mycelium. Also check the rootzone and plant stems for fly, moth and beetle larvae or pupae.
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