Leptosphaerulina spores indicate the cause of leaf spot. Photo: Luzmila Abercrombie
New disease ID service at SESL
SESL has always offered a complete testing service, covering soil, water, plant tissue, pesticides and much besides. To do this, we have had to send out some samples to outside specialist labs, many of whom we rely on for their excellent work.
For plant disease identification we have previously relied on government labs, whose work is faultless but slow. (This is no criticism of the plant pathologists, who are world experts.) In the case of disease identification, growers need an answer now, not next week: they’ve already held the funeral by the time the result comes back. Knowing what killed the crop is not as useful as stopping it in its tracks.
In-house disease ID service
So during the past year we have begun to build up our own in-house service, with a result in 24 hours.
When a sample arrives, our Lab Manager, Luzmila Abercrombie, selects some leaf tissue and roots that look abnormal. Under a microscope, first at 10× magnification, Luzmila inspects the specimens for signs of disease. When she has located a spot, at 40× magnification she then examines any microorganisms she finds there. Each fungal pathogen has a characteristic appearance under a microscope. Common ones are easily recognised. Less common ones can usually be identified in one of several disease identification references in our library.
Through the same microscope, Luzmila also takes a photograph straight to computer.
Luzmila places the original sample in an incubator for 12 to 24 hours to encourage fungal growth, and then repeats the identification. Any other potential pathogens, such as nematodes, are noted but not identified.
The results are expressed on a five-point scale as nil, low, moderate, high or severe, and reported back to the client, along with the photograph and a recommendation for what to do next. A moderate rating indicates that monitoring is required. A high to severe rating indicates that action needs to be taken.
Common diseases identified
|
brown patch |
Rhizoctonia |
|
Curvularia leaf spot |
Curvularia |
|
Pythium root rot |
Pythium |
|
Pythium blight |
Pythium |
|
Fusarium patch |
Fusarium, Microdochium |
|
take-all patch |
Gaeumannomyces |
|
Leptosphaerulina leaf spot |
Leptosphaerulina |
|
spring dead spot |
Leptosphaeria |
|
Helminthosporium |
Drechslera, Bipolaris |
|
anthracnose |
Colletotrichum |
|
dollar spot |
Sclerotinia |
|
red thread |
Laetisaria |
|
grey leaf spot |
Pyricularia |
|
downy mildew |
Sclerophthora |
|
rust |
Puccinia, Uromyces |
Disease control
SESL has always taken a holistic approach to any cultural problems. It is better to understand the whole of the production system and identify the source of a problem than to treat the symptoms. So our recommendations for resolving plant diseases focus on cultural practices – watering, drainage, nutrition etc. – and not on fungicides. In the long run, it’s cheaper to maintain a healthy production system than to spend money applying poisons. (Of course, sometimes a quick chemical spray is all that stands between profit and ruin.)
What to send
Send us a sample that shows typical disease symptoms. Include plant tissue, soil and roots, as appropriate. Aim for around 500 g. The sooner it can arrive, the sooner we can return a result and the sooner you can save the turf or crop, so use a courier.
In addition to the sample, we need to know the recent weather at your location, cultural details, how long the problem has been noticeable and any other details you can tell us that will help us pin down the problem.
We will return a PDF (by e-mail in 24 hours) or a colour printout (by mail) with photographs of the microorganisms we’ve found and recommendations for treatment.
Even better service shortly
We are currently negotiating to hire a plant pathologist to work full-time in-house on identifying plant diseases. We’ll let you know how that goes.