Photo 1
Photo 2
Photo 3
anything to be too alarmed about. In the case of fungal disease identification, the differences between labs should not be that great however, it depends on whether the lab looks for only the most obvious problem or whether it checks out potential additional or contributory problems as well. For example, a sward may show symptoms typical of Take-all patch and a sample may be sent in for confirmation of this disease. The fungus that causes this Take-all patch can readily be identified in the lab but, the affected plants may also show a secondary infection of Anthracnose, for example. If this secondary infection is also reported, the turf manager will be aware that a susceptible sward may develop a more significant Anthracnose disease in the coming months. One similar situation occurred in my lab towards the end of last year when turf samples were received for confirmation of the fungal disease Microdochium patch. The symptoms, shown in photo 1, were typical of Microdochium patch development and it was relatively quick to confirm that the sward was ‘alive’ with the spores of Microdochium nivale.
As a matter of course, I checked the
rootzone and, on first appearance, there did not appear to be a problem (photo 2). However, on feeling the strength profile, I considered that it was much weaker than might have been expected. It was a quick test to gently separate the turf from the rootzone and take a look at the roots. As you can see from photo 3, the root quality was very poor and far less than may have been expected from a mature turf. An extraction and analysis of the rootzone and of the washed roots identified a very high population of the Cyst nematode, Heterodera.
What was actually happening in this situation was that the Cyst nematode was feeding on the roots, weakening the root structure and reducing nutrient and water uptake in to the plant. With the plants becoming increasingly weakened, the leaf tissues were increasingly susceptible to the Microdochium patch. If the full result of the analysis had only been that the fungal disease was confirmed, I have little doubt that repeated fungicide applications would have been made to the affected turf
A good picture can often tell so much more than a detailed written
description
which would continually succumb to fungal infection.
Having been able to identify the main cause of the problem, i.e. the weakening of the turf due to the nematode feeding, management of the turf was focussed on increasing plant strength, reducing the nematode population and reducing the overall stress on the sward. Ultimately, this approach would strengthen the turf, lessen the outbreaks of Microdochium patch and reduce total fungicide input.
Where are we now with disease diagnosis?
We can identify the fungi that are associated with disease and, by considering the symptoms, and development of the symptoms, we can determine what the main problem is at any given time. In my opinion, a complete disease analysis should look for the possible influence of all pathogens, and that includes parasitic nematodes. The presence of these parasites does not necessarily mean that you will see symptoms of disease on the turf. As with all diseases, the symptom expression is affected by environmental and host conditions. If the turf is strong, a large population of parasitic nematode can be present with negligible effect on turf quality. That said, if the turf is weak, a low population can have quite dramatic results. When assessing for nematode involvement in disease, it is important to assess the quality of the root system in addition to determining the
population of the nematode. Never underestimate the importance of the background information or symptom history that you provide when requesting a disease analysis. It should help the lab to know the type of problems to look for and, if the suspected problems are not found or the symptoms are not consistent with those that are typical of a given disease, you should expect that the lab to try to find out why.
If you decide to send turf to a lab for analysis, work with the lab to provide them with all of the relevant information that can help confirm the problem. For their part, the lab should take seriously their obligation to provide a rapid, accurate and complete analysis service to help you best manage your turf.
To get the best result from a turf disease analysis:
• Take one or more representative samples to provide the best material for the lab to analyse
• Package the samples so that the turf does not get contaminated by the rootzone if you want a foliar fungal disease analysis
• Pack bulked 20mm diameter cores tightly in a sealed plastic bag to prevent the sample drying out if you want a parasitic nematode analysis
• Label the samples so that you can relate the results to where the samples were taken from
• Include your contact details
• Inform the lab that the samples are being sent and email photographs of the symptoms, if possible
• Provide a brief summary of the problem, e.g. chlorotic patches appeared across the pitch (evenly distributed) two weeks ago and have increased rapidly in diameter since they first appeared. Fungicide X was applied one week ago but there has been no change in the symptoms
• Send the samples by next day delivery wherever possible to ensure that the samples are as fresh as possible when they arrive at the lab.
Dr. Kate Entwistle, The Turf Disease Centre Email:
kate@theturfdiseasecentre.co.uk www.theturfdiseasecentre.co.uk
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