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Plant Pathology - Part 6

Michael Trevizo


Farmer, Agricultural Reformer, Production Manager at Five College Farms, & Soil Scientist with a focus on Soil Science and Agronomy; Education: Bacherlor of Science in Crop and Soil Science, Oregon State University.



  • January 15, 2019
    8:00 AM
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What I wanted to say about viruses is short live there's a lot of viruses out there the only way for you to know exactly whether or not your plant has a tomato or tobacco mosaic virus or. Cucumber mosaic virus or whatever other virus it could have is by taking that plant tissues and put in them in a crucible granting them down taking. Ally's a strip and putting it in there and testing it for but those allies trips are very expensive and they're looking for certain in zines that are produced by the virus so use of the virus comes in hijacks the cell gets the rubber zones to start making things for the cell blows up which is referred to as lie seeing it blows up releasing more viruses throughout the system that's how we get a cold you know that's how plants get a cold the trees etc That's how they get those viruses are immune system has to eventually develop or somehow develop an antibiotic towards or anti-bodies towards these viruses but anyhow would plant. What you end up with is that if the plant does not have the ability to notice that that's a virus so you have something going on with the century the copper are in AI then it cannot shut down some of these processes. That goes back to understanding the D.N.A. as well as having the essential building blocks which comes only through proper Trishul. The other statement I want to say is that those allies of strips work on the same principle as pregnancy tests where essentially looking for a certain in Zone A certain hormone if it's there it turns purple. You got it well those are very expensive so to be buying these allies the strips and you know figured out oh I just might get this right just might get that it's really not practical or cost effective it's best to just send it to a disease clinic or somewhere else and have it tested if you really believe that's what it is and I believe that the 100 percent convinced that you have a virus in your production system you need to have that plant tissue taken in verify that you have that virus because it's only until you know that you're dealing with that virus that you know what are the decisions you can make a so you could possibly search for. Variety set or have genetic resistance to those to to the virus or you need to think about what is vectoring that virus and for those of you that don't know what vectoring is vectoring is when something for example will say in a food goes somewhere and bites. I'll tell you the problem I had my neighbor grows tobacco tobacco has every. It has a lot of pathogens has been bred to. Resist a lot of different viruses so if you smoke or your husband or your wife smokes or your dad or your father or your neighbor smokes almost any pack of cigarettes you can pull off the shelf is going to test positive for tobacco mosaic virus and tomato mosaic virus so if you're growing so in a seize crops and you smoke or you somebody you know somebody that's most even shake hands with somebody that smokes after they smoke a cigarette and then you go and you decide to going to work on your crop you are going to take that virus from that cigarette and put it onto your crop. But that's not that during that during is when perhaps a food is on a tomato plant. It has a piercing sucking mouth parts that means it's going to penetrate the cells it's going to seek to take something out of that plant and when it penetrates that cell it could be contaminated with bacterial organisms it could be contaminated with viruses and then it flies away and it comes over to your plant and then it bites it and then it inoculates it with that virus so that bacteria that's referred to as vectoring on the spray here list there are certain contacts praise you can use they're not very popular anymore that I don't even think that that or I'm not sure whether or not they're listed on the right don't remember but those contacts praise the way they work is that they're trans laminar or they're systemic So say for example I take a certain product and I spray it all over my tomato plants or my beans or whatever and it's supposed to prevent a foods from coming in so that show up and if it comes in and it has the stuff painted on it coated on it if you will it bite on it and it says look this case nasty and then it flies off and it goes to another leaf and it bites on it look at this taste nasty and then it leaves that's essentially what those contact sprays are doing they're essential in putting this nasty flavor onto your crop so when the pest comes in and it bites down and says look this is gross however that a food or Beetle or whatever it is was recently on an infected plant it could come in and infect hundreds of your plants in just a day with whatever virus it might have and vector that disease so it's why you really don't want to use those types of sprays in your production system another thing I'll go on to say with certain pariah these of plants is that for. Over well over 100 years we have been selecting pretty much everything everybody needs has been selected predominantly for its production characteristics like Mars not in the room anymore and he was saying that you're paid for for growing calories that's what the farmers been paid to do so they're selecting crops for. Produce well and we have not selected species and selected genetics that have perhaps resistance to different pathogens or have perhaps can translocate more of a certain vitamin and be more or healthier to you in some way we have been selecting simply by production by yields and by tonnage and what we've done over the years now and this is actually a crisis. I can remember the gentleman's name but there's a very good I mean Myers is his last name and I say Mark Myers is his name but that's not right but anyway Myers is Jim Meyers that's his name Jim Myers in Oregon State University he is in charge of the plant of the breeding and genetics and. The concerns he brought to my attention is that we have been selected for yield to such a point where we have almost no capacity to. These plants have almost no capacity to resist new pathogens new diseases that are coming out that may not even be new they have always been there is just that they weren't here they may have been brought from other parts of the globe and brought to the United States. So we have really complicated that So now the next thing that we're trying to do or the other issue is we have also selected plants that don't have the nutritional content that we really need as human beings as the human race so this is causing problems. And our food production system so now the next the movie that he was trying to make or at least suggesting that we need to make is that we need to start selecting genetics and going back to wild types looking for wild tomatoes wild potatoes so you know they came up with the recent The Simplot came up with it in a potato which is genetically resistant to late light Well where do they get those genes they got it from a while type of potato that grows in Peru However they use modern technology to take those genes out of that variety and put it into a newer variety instead of describe breeding and cross breeding to use a lot of the potato that's genetically resistant so we have issues that are food production and a large portion of our seeds that we have do not have the genetics that were originally there because we have not been selecting for those genetics and we have been doing this for all very long time as a human race so that's one of the biggest issues so when we start to argue about heirloom or not heirloom I don't really think that's a valid argument because there's really no real thing as an heirloom and furthermore almost every seed that's out there was selected by some farmer for some reason and usually that reason is production and not nutrition so anyhow I have a whole. P.D.F. on different varieties and different nutritional content and different vegetables and when you start looking at it you realize wow. You're. There such serious swings I mean like beta carotene for example beta carotene as you know to Vitamin A is put together it's a perfect too perfect Vitamin A is put together well. The orange the color has been bred out of our food system and everything you know all the tomatoes are red now well red tomatoes compared to orange tomatoes have maybe 25 percent of the beta carotene but how often have you walked in the store and found an orange tomato. You you never find out so things like that other issues as corn and I mean I could go on all day with that but anyhow that's just with reading so to get back to viruses which is really the topic here that during is a serious issue trying to proper nutrition for the planet can defend itself so we can see like we saw in the video that has the capacity to recognize that it's being invaded and fight against that is a big issue. Let's see testing for testing for a. By resist that you have whatever that virus is that you might be concerned and concerned with it's always best it's always going to be cheapest to just take it to the disease planet Eliza strips are very expensive they're like $300.00 a pop or something you don't want to you know buy that and then find out it's negative it's something else so you got to spend another $300.00 to see that's maybe tobacco mosaic virus or something else I don't know but it's just it's not practical. So I'm going to move off now to the last portion to finish this up we will go to. Disease development and pop populations of plants and you know how fast is the speed how many is the efficiency how far is the associated with the movement that C OK so can a contagious poly seqlock disease epidemic is typically described by an S. shape disease curve I'll show what that is the overall speed of the curve can be summarized in infection rate per pair a meter are so if you take biology the courses they talk about are strategist which is saying simply that they reproduce very quickly so there are strategies I mean an organism a figure organisms that are born pregnant so I imagine born. You're not going to you know somehow out reproduce that thing if it decides to take off it takes off so that's why our strategies which is a potential birth rate or birth rate of a new disease. It talks about the magnitude of our won't really get into that high value of our rate generally lessens the benefit obtained from OK so if it's a high value of our Like for example late blight is a example of a high rate of powdery mildew could be relatively high most your viruses are relatively high as well anyhow with a really high our rate sanitation is not really the key. Was saying when we go to these greenhouses and they can get in all these suits and there's no I mean very dogmatic about keeping the place clean and I just chuckle because the wind can just blow from a different direction and the whole place is an ocular and multiple greenhouses I mean this happens in the greenhouse industry they had a white fly outbreak or all they had a late or early blight or whatever at Bracken no surface area now break and edges wipes out their crops I mean it goes to these these hydroponic facilities and it wipes a mountain hurry I know a couple different one facility in Arizona totally wiped out in a matter of a month. 180 acres of tomatoes in a in a greenhouse wiped out I mean in a matter of a few months so you know people think hydroponic is the farming of the future it's definitely not. It's the farming of the present it's all it was of the present it's what they're doing right now. So here's an example of a. Disease in the timeline so when you try to practice sanitation and so studies have shown that even a secured to. A 2nd curve was generated even after 80 percent reduction in the primary knock them so they go in the sanitizing hope place people talk about what if I go in and I spray all this stuff and I kill everything the whole room the roof the ceilings the ground I burn and I spray whatever Saturday is a fine example but there's other things. Going and you reduce 80 percent of your an ocular and all that does more than our rate of point 2 which isn't even really that bad by $8.00 days all it does is push this down and when we start looking at different diseases and when you see and different sprays that you can actually use most of these sprays all they're doing is slowing down the germination of the fungal spore So all they're doing is buying your time which is why when you read the label it tells you Spriggan every 7 to 14 days why because all you're doing is delaying the germination maybe 7 to 14 days that's so all you're buying is 7 to 14 days. Dependence is like being on insulin who wants to be on insulin nobody wants to be on insulin you know you want to get over the disease so this is really not that great of an approach to think that either sanitation or some spray or another that's going to prevent that from happening all you're doing is this cat and mouse game buying yourself time buying yourself time hoping that you can get maybe this mid curve somewhere down over here the harvest season where you won't have to deal with it until you've taken harvest that's just I don't know. I don't like to play that game I don't know who likes them anybody in here that foreigners like to play the game like to play again. What the government shutdown Oh yeah. Sounds like the US federal budget right is just pass a budget for a month that's not fix the deficit past kick the can down the road anyhow so disease avoidance avoidance disease by avoiding the pathogen or by altering the environment you know your. Cultural practices are targeted at one or more of the components of the triangle so you know you go in and you sanitize the whole place what do you do you're essentially get rid of the pathogen you're trying to get rid of the pathogen but like I said there's so many spores I mean billions and billions of spores just. On one leaf so when you have a heavy into station like these greenhouses that were heavily in the state of these are 180 acres to come in and sanitation sanitize that there's a ton of work and you think it's going to really you know take care of the problem No I'm pretty sure there was more issues than just sanitation but it's what they like to practice so. Avoidance measures targeted at the pathogen usually principles of control target the pathogen exclusion eradication avoidance you know avoidance of the past pathogen is industry migration so this could be you know essentially well if you're garlic is going to get hit by a certain. Fungal pathogen will they stop growing garlic Well that doesn't really help you if your market is garlic. To markets corn you don't want to have to switch to beings if there's no market for beings you know so that's not really a good practice but that's typically what they do squash is another example out in New England after a sissy is knocking out the quads so people are saying well we have very little acres to grow squash but nobody really goes and addresses the nutritional issue that's the problem with the fight after which suggests what and home I see. So my seat fungus a lot of these a lot of these squash fields are right on the Connecticut River they're waterlogged soils their nutrient deficient and their water logs I mean it's just it's just silly you know you really you got to look at the nutrition crop rotations of course is a very common practice everywhere planting date or harvest date changing it to where maybe you're trying to get ahead of the head of the pathogen so you know some examples are trying to get the potatoes in early before the potato beetles come out you know you're just you're just playing with timelines you're not really fixing the problem but a lot of a lot of different extensions will recommend that you do things like this. That see and growers as well disease avoidance by modifying the environment so change the amount of water changing you know if you've got grow lights. You might have to give it a rest temperature adjustment in the greenhouse Maybe you need to put up a shade cloth in your greenhouse and cut the heat little bit because the sun down a little bit and of course atmosphere maybe you need to get some fans in there multiple things you can do maybe you're growing things outside of the growing season and you need to adjust that but these are all minor changes that you can make to your crop see another one is irrigation man it is a really good example of psyllium wilt on potatoes an example here see suppress disease development by deficient irrigation early in the season so what they do is that they plant you can plant your potatoes in the season and then you're going to irrigate another we're going to give them maybe about. 60 percent to 70 percent of the actual water that tomato would call for until you until you get to the tuber initiation stage what's the tuber initiation stage when it flowers here so soon as a crop flowers you go back to normal or a Geisha and once you go back to normal irrigation you're dealing with a. What type of fungus. And I see from his I'm sorry ask him I see from his so it's going to want high humidity environment so you reduce your irrigation in your dry at 1st so that you don't produce the environment that is necessary for that fungus to take off however you're tuber a long eared tomato tubers some folks say about every 4 days a need to be water and if you don't water and you start to actually plant starts the pool the moisture out of the tumors so you want to put that water down to really swell those tubers up and get bigger potatoes so you go to you move over to normal irrigation level and then you go to your harvest so that the diseases in the set of starting over here at the planting stage starts at the super initiation stage which could be 60 days down the road so just buying time but you haven't fixed the underlying issue which is nutrition usually And of course this is a bigger issue with wet soil so Here's a graph of yields you know kilograms for plot on. Deficient it was definitely a little bit less than the optimal water but. You know excessive water reduced the eels that much to where really the disease really took off so you saw $1.00 instead of one point so I don't know $2.00 to $3.00 or so kilograms per plot. This is just an example of how irrigation really changed your yields. And going deficit in a different practices that we had there let's see here alright so management a fuller leaf wetness is going to affect detritus and your strawberries Oh yes so here's another one how many you know how many hours does the spores need to be wet before decides to initiate germination what we're looking at here so was the try to spawn strawberries $8.00 to $32.00 hours is all it takes it is temperature dependent but just $8.00 to $32.00 hours of the leaf being wet or the tissues being wet is all you need to try to take off right so if you can keep that leaf. Dry it's less likely that you need to worry about that for taking off with books any onwe it's $9.00 to $15.00 hours it's clear to me on be descended to into 2 hours so now look at this example is a fine example of when you should such irrigation times if you have control of your game time so we look here at. Leaf wetness intensity so in both of these studies in both these plots here the same amount of irrigation water was put out it was just put out at a different time so at 1st you start watering at 6 in the morning you water for 4 hours so you're down by 10 in the morning at that point the sun is still high you still have enough heat in the day we are talking about here. In the late spring or summer time there's enough heat in the day to dry that leaf off so what you do but what you notice you're only have me be a maximum of the 11 hours of actual leaf lettuce right now let's compare that to you decide you want to irrigate at 12 pm which is noon and you're going to irrigate for 4 hours and you're going to turn that center pit or you're going to turn your sprinklers or whatever off. 4 o'clock and at this point the sun's already on its way down the day it's cooling there's not enough heat to dry that leaf that leaf well may stay wet clear until about 7 or 8 o'clock in the morning you see the difference of how many hours the difference in hours though you irrigated and you put the same amount of moisture on the same crop the actual length. Of leaf wetness in this scenario is about. Goodness what is that about 18 hours so when you decide to irrigate how much water you put down is not just about how much water but it's also about what time you decide to irrigate and how that's going to control the leaf wetness so then you look at the duration of leaf leaf wetness when you water at noon it's much shorter and it's straight linear regress regressions So you're really you want that leaf to dry off so that you don't get these fungal spores taken off you know and these are all things outside I mean we're here all we're doing is altering the environment we're not changing the host we're talking about how to change the environment and this of course was done in periods followed by sunny days so this was a sunny day it was not a cloudy day another here this is another thing we can do I talked about an earlier these are great control learning. To try this or Bunch rot on grapes is the leafy So what they do with these vines Here they come in the center and they get rid of all the leaves right there in the center and the problem what happens largely with with grapes is that they produce so much foliage if you don't come in and remove that foliage you develop these microclimates of excessive humidity inside of the inside of the plant and then you start to fight pathogens so coming in appropriately managing this getting you're getting your labor to keep the leaf keeping that area the leaf as well as it's sometimes it really helps to go in and prune this. And. A couple other things but anyhow that really drastically reduces the amount of moisture or answer humidity that you'll find in that leaf and that will keep the try this and as well as powdery mildew down and here's an example of before dealy thing and after leaving you you couldn't even see through the thing and now you can really see through the thing you get the sun coming in and drying drying the leaf out. So this is the for moving grade so here fuller canopy management so now we're talking about row spacing and with what with respect to white mold control and soybean So way back in 1995. And what more this relatively new disease in the U.S. soybeans in the seventy's soybean yields were greatly increased by seeding with grain drills which put the rows real close together and then instead of a row planters the narrow row spacing however allowed to build up in the production system the current trend is now going backwards people are start actually spread the rows out and let the air get in there and dry that the foliage up to reduce the incidence of square 20 on soybeans it's just another example of how reducing opening up that canopy drying up that leaf is going to reduce that incidence of disease of course their disease avoidance by managing a host of abilities the size genetics what else can we control nutrition that is changing attrition nature and frequency of moons is the other things so nutrition I'm not going to get into a talk about it tomorrow if you want to hear what Mark talked about a whole bunch. Gregory's talk about a whole bunch in the last years but I'll talk about it tomorrow the next thing is nature and frequency of wounds so here's some common farm practices we'll talk about here in a minute so we're looking at pairs here. Pears like most other stone for you know you harvest them then you've got to put them in boxes and put them away and you know over the winter and the next year you go out selling these products so you sell your harvest throughout the year you don't sell it all on you know shortly after the harvest so here we're looking at Gray mold in. BLOOM old bulls eye rot. So what causes these pathogens to take off in the storage room this is referred to as the middle Lamela the area in between yourselves I calcium content and the makes fruits more resistant to decayed study after study has figured this has answered this question question is how do you get that calcium in there so root organisms use in zines to dissolve the middle of Mela between the cells the higher the calcium content in the middle of metal between the cells the lower the incident of fungal pathogens on your fruit in storage so if you want to increase the storage of your apples and oranges Yeah even your oranges and your even though that citrus but your apples and your pears except on your other stone fruits you really got to get that calcium levels right in your orchard as I talked about nitrogen as well so oh yes I forgot to put this in here so this is nitrogen so nutritional status of fruit at harvest in scenario one all right so what happens a lot of talk about this earlier I forgot that I put these flies in here abundant nitrogen excessive vigor no matter the crop it's always the same you end up with fruit cup competition so what are you competing so you're when you put do when you produce excessive vigor through excessive nitrogen you have the mirror's Mary stem the Mary schematic stem cells which are the tip of the shoots they're trying to grow more lethal foliage and then you have your flowers which is referred to as a floral stem cells are competing for nutrients. And when this happens usually end up with. A board and flowers a lot more flowers tend to abort as well as. Density and then in the Postle with low fruit in the calcium which promotes rot Orient up with just excessive nitrogen in the fruit which also promotes rot. So this is these are studies where they've looked at these very things I mentioned earlier managing the nitrogen making those applications of nitrogen at the right time not putting those fertilizers in in the spring where you're going into your. Floral stage where you get rid of put out your floral buds because what that will do is that if you end up with too high of a cow's in the nitrogen ratio you will end up blocking calcium and it won't make it into the crop it's best to well they suggest anyway that it's best to put any nitrogen fertilizer this down in the fall that's the extension recommendation Anyway I have other recommendations but I won't really go into I'm right now so nutritional status of fruit at harvest scenario to have moderate vigor and Ortrud calcium sprays so they actually did studies where they went around spraying. To dead of forms of calcium I think was calcium chloride that was used and so you know with more high higher calcium content in the fruit which leads to direct inhibition of fungal enzymes which is more resistant to fungal decay or you get less mature fruit slower respiration and senescence which means. The fruit is not pushed into it doesn't over mature making simpler or easier sugars which are more likely to die cells are going to actually die once they get to write as we've seen in the refrigerators and then of course fungus comes in and takes over just like you see in the refrigerator when something is spoiled and it's all nasty that's fungus that's gone on it. OK there so we look here oh yes this was a study that was done on the effects of calcium sprays and storage atmosphere on pear decay so what they did is that they're putting C O 2 into some of these storage units where they have pears and apples to try to lower the incidence of fungal Rots of the fruit so they looked at different. Scenarios here where they did 20 percent C O 2 with Field Treatment of calcium and then they look at the average lesion diameter and the and the amount of bloom old and grey mold as well as the percentage of wounds that were affected so what we see is when we went to 20 percent C O 2 in the atmosphere of the storage room as well with calcium treatment we had about point 5. What were the incidence of mold development a bloom of development on the fruit 1.9 in the grey mold 6.8 the blue mold with the the percentage of wounds in fact it was 6.8 over here with a great hole that was 20.8 So with this side it's really the one that's more important because you look at the number of wounds on your fruit to actually got infected with mole so what you saw is that the best scenario here was 20 percent C O 2 with calcium treatment. At in this is calcium treatment in the spring when you're putting out flowers folks this is not calcium treatment when it's in the storage room all right so we see that there was a grey mold with 20.8 percent if you go down here to pure air no calcium 99.2 percent and you see all the betweens that definitely goes up significantly and you look even at just pure air in the store room with a calcium treatment was still considerable considerably a considerable an improvement from compared to without it which is really interesting to load and it really makes a serious difference when we're looking at the actual. Number of wounds when you see one 1st off wounds are really important the wounds is where the the molds want to grow why because they don't have to have the enzymes to break those walls the walls are already broken so when we're looking at the food that you're putting into storage for to go over the winter or throughout the year you look at the different punctures and buds scratching buckets Strat staples and other things that destroy it and then they did studies to just look and see what what what how do we get these wounds on the fruit so they ended up with the scanner plot and you know at 1st this is kind of confusing you see skin skin wounds versus fruit firmness and these are 2 different studies that were done so when you actually highlight how they were playing their employees that were collecting the fruit then all of a sudden it makes sense so when you look at the bins that were that were put together by the people that were paid by the bin to collect it this is what they found an average of 13.9 percent of the fruit was Dan had some sort of damage to the skin when you look at the bins that where folks were paid by the hour. It was only 4.3 percent. So how you pay your harvesting crew has a lot to do with the kind of the quality of the product you're going to have in the bin when you go to put it in storage this media was brought to you by audio 1st a website dedicated to spreading God's word through free sermon audio and much more if you would like to know more about audio verse if you would like to listen to more sermons lead to visit W W W dot. Org.


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