Dr. Margret McGrath, Cornell University
Dr. Sally Miller, Ohio State University
This clip is from the Late Blight Control in Your Organic Farm Webinar
So we've seen some things that it's not and we've seen some symptoms of late blight, so it can be a confusing disease. So how do you be sure, how do you confirm that what you've got is late blight? So the essential lab we do is microscopy. We have a trained person in there who can recognize it. It is a very simple and quick thing. Sometimes we have to tweak things a little bit, we might use moist chamber, but this is the quickest and easiest way to do it as long as people are trained in microscopy and they know what it looks like. But there are some other things, there some kits that are available on the Internet and they can be purchased so if you want to try them on your own farm. They are a diagnostic test that is quite similar to a pregnancy test; it's the same technology. Quickly I'll just say there are two different types with the same technology just different formats. It will always have two lines, one is your control, right here and then if it's a positive you'll get another line. So two lines means positive. You can see here that they are quite expensive this is a British company that makes them but they are distributed by this company, Safeguard Biosystems in Canada.
A more local type and it's a little bit simpler format. It's from Agdia, it's this Indiana company. Again, a very quick test and the results are quite accurate and again that's a quite a lot less expensive than the other test, but you have to buy at least five. If you buy five it's about thirty-five dollars and then if you buy twenty it comes out to about five dollars a test. But these can be used and sometimes if we have trouble in the lab we may use these if we can't get good sporulation.
Ok, so if none of those appeal to you , you're not sure about the symptoms and you don't want to buy a test, you might find a diagnostic lab to do this and while there are some commercial labs up today, I would just like to mention the U.S. National Plant Diagnostic Network and that is composed of diagnostic labs that are mostly associated with land grant universities like Ohio State or Cornell in every state. And they are divided into regions and if you go up here and if you look up here on the left where I've circled that, each of these regions: the Great Plains Diagnostic Network, the more central, for example, north east is where Cornell is and north central is Ohio. So if you just look at the Ohio one right here. If you go into this North Central Plant Diagnostic Network, click on there and you'll find a list of the diagnostic labs in each state. And for Ohio, I'll show you here what comes up is the Plant and Pest Diagnostic Clinic in Ohio State University. They tell you how much it costs to send in a sample, how you submit one and etc. and you can contact the laboratory if you would like to submit a sample.
You can also get help with diagnosis through your county extension office, again, you could contact a clinic directly and in some states like Pennsylvania for example, the departments of agriculture do have diagnostic services. And then there is other information available on disease identification. You can find them in these fact sheets and websites and also a very good book is called The Compendium of Tomato Diseases, there is also one for potato, by APS Press in Saint Paul and you can find that easily by googling. And you get all of the tomato and potato diseases in that.