 All right. Good morning everybody. My name is David Lawrence. I'm the REA for Central Alabama commercial horticulture. I'm going to talk a little bit about soil-borne pathogens and vegetable crops. Just kind of a basic overview. Not going to dive in a whole lot into certain pathogens or control methods, but just kind of a basic overview. Happy Halloween. Sorry, I didn't dress up like Eric. Maybe next year. Some of the topics we're going to talk about, just going to look at some terminology, then different pathogen groups, factors influencing infection, diagnostics, and control strategies. All right. So why are we talking about soil-borne diseases? They can significantly reduce yields and quality in fruit and vegetable crops. I threw fruit in there because a lot of the fruits that we manage, for instance strawberries, we treat those basically like we would a annual vegetable. And then even some of our shorter lived fruit crops, they can have a significant influence on those. They often survive for several years in the fall. That's what makes them so hard to control. It's not just a quick fix, sometimes we can spray and then get on a two-week rotation like we do for a lot of other diseases. These can survive for a long time in the fall. And then simultaneous infections can cause a disease complex. What comes to mind for me is in strawberries, black root rot, that's often a complex of whether it's pithium, rhizome, nematodes. There's a disease complex, so that really gets complicated when you're trying to rotate or for other controlled methods. All right. Some of the terminology, just basic pathogens, those are the biological agents that cause the problem. Symptoms are the visible reactions of the plant when it becomes infected. So if you're out in your field and you see a plant that's wilting or off-color a little bit, that's the symptom. The sign is the visible evidence of the presence of the pathogen. And so that's going to be the sclerotia, bacterial ooze, mycelial growth. The picture that I have there is southern blight on tomatoes. And that's what comes to mind when I think of signs of the soil-borne infection. It's very easy to diagnose in the field. You see that white. If you look at the base of the tomato plant, first you're going to see it starting to wilt. Often you'll see it kind of working its way down the road. And if you go to the base of that plant, you're going to look down, you'll see that mycelial growth, those orange or brownish sclerotia. And that is a tell-tale sign of southern blight on tomatoes. Inoculum is a biological agent that is able to affect the host. So whether it's the spores or mycelium sclerotium, what's going to stay in that soil and affect future plantings? And then just soil-borne pathogens, the pathogen that causes plant disease through contact with the soil. The different pathogen groups are fungi, bacteria, virus, and nematodes. We'll look at these real quick. Fungi is far the most numerous. It's the most economically important. No pound for pound. I don't know how these compare to the other groups, but it is definitely the most economically important just because of the vast number of pathogens in this group. They are the winners as far as persisting in the soil for the longest amount of time. And so some of the notable fungi pathogens include phytophora, pythium, rhizoctonia, sclerotia, or pluritinia, fusarium, and verticillium. You know, almost all of these are very important on crops such as tomatoes or peppers. So if anybody grows any of those, I'm sure you've probably had a run-in with some of these before. Fungal pathogens live on plant debris or other organic matter in the soil, or they can survive as free-living organisms, and they can survive in a wide range of environmental conditions. The picture on my left is with a little tomato seedling is damping off. And so if you see this, a lot of times you'll see this in a greenhouse or planting early in the year. You'll see that right above the soil line looks like the stem is pinched. That is a sign of damping off, whether it's pythium or rhizoct. I think this one was pythium. And the picture on the right is a okra seedling. I think it was a week or two from sprouting after sprouting. And the whole road looked like this. Pulled this seedling up, and I believe this one came back as rhizoct. We just had some, had a wet planting. Bacteria are not nearly as numerous as fungi. Most of them do not persist for long periods of time. So there's some of the common ones, Romania, Rhizonomus, and Streptomyces. Streptomyces is fairly common on potato, and so this is a sweet potato soil rot. Streptomyces also causes potato scab. Viruses are extremely rare. I don't know if I've ever seen this in person, a soil-borne virus. Latest big-name virus is maybe one that you might have heard of. It can also, you know, has to have living, like most viruses, has to have a vector. So it has to have living tissue to survive or can survive in nematodes or fungal vectors. And then lastly, nematodes. Most everyone knows what nematodes are. They're non-segmented microscopic roundworms. Plant parasitic nematodes spend their lives feeding on plant roots, on or in plant roots. Fields infected with plant parasitic nematodes will have reduced yields and reduced quality. This picture that I took here was a couple years ago. It was in a really large tomato operation and he had a section of his field that the plants looked okay. But when he got through harvesting at the end of the year, he noticed his yields were way down. And so after looking around a little bit, collected some samples and pulled these up and sure enough, most of the plant's roots look like this. You know, it's not really something that if you hadn't had other numbers to compare it with, you might have just thought he had it down here. But no, probably a 10, 15, 20% reduction in yield because of these root not nematodes. All right, so factors influencing infection, the soil type. And with that comes moisture, whether it's sandy loam or a heavy clay soil. Typically, the wetter the soil is, the higher the water holding capacity is, the bigger incidence of soilworm pathogens you're going to have. What nutrients are available? What nitrogen source you're using, depending on what nitrogen source some pathogens thrive off of the sources that you're using and soil pH. Some pathogens are basically non-existent, whether you're below a certain pH or higher pH. It's not a set scale for every pathogen out there. It just depends on what pathogen you're dealing with. Full temperature, a lot of our vegetable growers are using plastic mulch and so you can plant a little bit earlier in the year. And so you're dealing with some of those damping off like pithium. The cooler wetter temperatures are going to be more conducive for development of that pathogen. White plastic versus black plastic. We don't use a lot of black plastic in the middle of the summer because it just gets too hot and you're going to put more stress on those plants and develop an environment that's going to stimulate that pathogen development. And then planting day, just kind of goes with soil temperature. Of course, the lander will wait in the year. Kind of get out of that cool spell, but also we get more into, wait too late, we get into too hot of soil temperatures. Cultivation practices, sanitation, are you keeping your field clean? Are you getting that old plant debris out of there? And then what was your previous crop? No crop rotation. We'll talk about it in a minute, but crop rotation is very important when you're dealing with soil pathogens. Diagnostics, it's pretty hard to diagnose these in the field unless, like I said, Southern Blad or something or damping off something that's really got those key characteristics. Otherwise, we really rely on our plant diagnostics lab. But when you're looking for, we're trying to diagnose the soil pathogens, you need to observe the whole field. This picture I have on the bottom left is, it's actually a strawberry field, but like I said, we treat strawberries basically like a annual vegetable here. If you'll notice the third row from the bottom, those plants are a quarter of the size of the other rows. And so I notice, this is a huge field, doesn't represent this picture, but this little area of the field was really stunted. And so we took samples and I don't know if it was holding water or didn't get treated the same. This is actually a fumigated field, so I suspect this row might have gotten skipped during fumigation, but came back as Rhizoc. So when you want to collect samples, you want to collect the entire plant, including the roots, and you want to collect plants that have healthy tissue and infected tissue. You also want to keep records of disease for confirmation when you're planting next year. Easy to remember for a week or so, but come this time next year when you get ready to plant, it's easy to forget what areas weren't affected. So try to keep good records. Control strategies, host resistance is a big one. And so if you know, on the right there, I have just some tomato disease codes. And so if you know that you have fusarium wilt and you don't have the option to rotate, so you've got a small acreage or you're planting at a high tunnel or something, you want to go through there. And the first thing I'm going to do is select varieties that have fusarium wilt resistance. That's the easiest way to overcome that. Operation as I mentioned is huge. A lot of these fungal pathogens especially can live for a long time in the soil. So the more we can rotate and keep host out of that area that are vulnerable to these pathogens, the better off we're going to be. Irrigation practices, we want to maintain optimal soil moisture. And a lot of that is going to be utilized through drip irrigation. Drip is a way to keep soil moisture where it needs to be, where it needs to be, and also plant well-drained areas. We want to try to avoid low line areas that are going to hold moisture. Try to plant areas that are going to drain for us when we have heavy rain events or increased irrigation. Again, sanitation or moving plant debris, clean your equipment if you're rotating from field to field, plowing or laying in plastic. Try to clean your equipment if you've got an area that you know has some of these pathogens. Wash it off, clean it off before you move to the next area. Planting practices, timing. Again, we talked about that with the soil temperature, the depth. How long is that seed going to take to emerge? Using seeds versus transplants. Again, like damping off, that's one of the advantages of using transplants is you kind of give that seedling a head start. Use disease-free seed or transplants. And then also utilizing cover crop, for example, mustard has some pathogen-reducing properties. When you grow that crop out, till it in into your soil, it can help reduce some of those pathogens. And soil solidization, which is ideal for small areas or raised beds. So we have a video on that on our HHS website. All right, then chemical control. Femigation is, I say, mostly effective. It's not a cure-all. It's not a guarantee. It is very expensive. It requires specialized equipment and additional license. So there are a few growers that still do it. Most everyone that I know that doesn't get to hire it out gets a contract about through an independent contractor. But it is an option. Conventional control or conventional chemicals, they can be effective. The application is critical, getting that product to where it needs to be, doing it at the exact right time. And then, of course, choosing the right product for the job. If you're looking into chemicals and you're not familiar with this, this is just a page out of our Southeastern U.S. Special Crop Handbook. You can look that up. There's a PDF of it online, if you don't have one and don't have a hard copy. And so you would just go to whatever you're growing. This was a page from Tomatoes. I just picked sun and blight. And so you can see there the products that they list, the group numbers. It's important always to rotate group numbers if you're doing, you know, season long control. And then it tells you there, you know, I mean, as you can see, most of these says disease suppression only. So these aren't, you know, aren't cure-alls for these pathogens, but they will help. And that's it. If you have any questions, you can reach out to me or any of the other agents in your area. We'll be happy to help you. If you have any questions, please let me know.