Tomato disease issues

[hendi_alex]

I'm considering an experiment. Am wondering if pinching or snipping lower limbs, especially those in contact with soil, is a major entry for bacteria into the plant. Every year the southern blight or summer blight makes its way, slowly at first and then rapidly in July, up the plant until finally nothing is living except the stem and the upper terminal growth.

This year I'll take a few transplants and not trim them at all. Will try my best not to cause any cuts or abrasion, and will see if those plants are more resistant to the effects of those persistent mid summer diseases.

I'm also thinking of covering a few plants from rain, so that rain never wets the foliage. And will probably cover with some shade cloth near the end of June. I've noticed that my nursery plants growing under shade cloth or in morning only sun seem not to be affected so much by disease.

The last thing that I may try is a weekly spraying of copper sulfate and white lime solution (Bordeaux Mixture). While the mixture is approved for organic gardening, if used, I'll likely only use it on a few plants, and will use it in limited way so that very little gets in the native soil.

Almost none of my mature tomato plants have been making it through the hot, humid mid July to mid August period. I would be interested in thoughts related to my comments above, or would be interested in what others of you who live in the hot, humid south do to combat these mid summer tomato plant destroying diseases. Bacterial resistant varieties seem to die just as readily as heirloom varieties or others, so am looking for some reliable strategies to manage this problem.

[imafan26]

Sounds like a good experiment. I'd like to hear how it turns out.

I regularly pinch off the lower branches of my tomatoes because they always get ugly. I usually wait till the plant is growing a bit since I plant my tomatoes very deep.

Drip system around the tomatoes help with the splashing water.

Tomatoes grown in earthboxes are watered through their watering tubes and not from the top. It also helps with BER since mine have a 5 gallon reservoir so they stay evenly moist. I do not use any lime on my tomatoes.

I fungicide only if it rains heavily for days and if I know in advance that rain is coming, I can spray with a horticultural oil to help the leaves repel water otherwise I spray within 3 days of the rain stopping. It needs to be one or the other it cannot be both. It is the humidity after the rain that allows the fungi to grow and not the rain itself.

For heat and disease tolerance. I choose tomatoes with resistance to the common wilts (3 races of fusarium), and nematodes (unless they are grown in pots). To get through the heat of summer, I grow heat resistant tomatoes that will set in hot weather up to the 90's. HeatwaveII, SuperSioux, Early girl (surprise! it stops producing in the hottest weather but comes back and survives), big beef, celebrity,Arkansas Traveller, Quarter Century, green zebra and Supersweet 100.

Univ of Florida has come up with solar fire and some other heat resistant tomatoes. Unfortunately they lack the disease resistance so they did not get past the seedling stage for me.

Make sure they have the space they need for good air circulation.

[TZ -OH6]

the experiment is certainly worth a try.


One of my tomato plots is alongside the house and is protected from a lot of rain by the roof eaves. The year the midwest was wiped out by late blight, those plants resisted for several weeks longer than the exposed garden hit by rain. But I have not seen a difference in septoria and early blight between the two areas (spotty leaves) -- maybe because I wasn't looking. The 'books' say splashup causes infectiions, but here the spores blow around and plants on newly broken soil and mulched soil get infected quickly. Pruning bottom leaves helps, but the plant needs them to get started so I wait until they get infected.

My yard is surrounded by a weed field. things might be different in the manicured suburbs.


Southern blight girdles the stem just above the ground and kills the plant quickly. It sounds like you are talking about one of the wilts that get in the plant's vascular system through the roots and then climbs up the plant.

[hendi_alex]

For the most part, it is the same every year. Around mid to late June, as the temperature and humidity rise, the lower leaves begin to yellow, sometimes accompanied by spotting. The yellowing is soon followed by complete drying and turning brown. The yellowing slowly moves up the bush, until sometime in July, after a rainy period, the yellow explodes upward, usually only leaving the tip growth alive, and sometime killing the entire plant.

My only defense to date has been succession planting. The young nursery transplants which are growing in morning sun only, tend not to be bothered very much by the disease. Transplants that are moved to the garden after the temperatures drop back under 90 degrees or so in late summer are not affected much. It is just the middle part of the summer that causes such a disruption. Last year we went for about 3-4 weeks with very few tomatoes being harvested, because most of our plants had died in early to mid July.

[applestar]

Contributing to possible experiment ideas

-- practice fruit tree pruning precautions -- prune when amterial is dry (after dew has dried, etc.), use only sharp tools to prune, sterilize tools and cuts (I spray with alcohol with a $1 store travel mister) after/before each cut.

-- use AACT as soil drench and foliage spray

-- try one of the lab grown concentrated single organism like Actinovate or Serenade.

-- dip hands in concentrated protein dry milk solution to keep from spreading the disease from plant to plant. (I'll go look up the protein % though I have posted this before. I'll also see if I can find the ref. source link.)

[Dillbert]

most of the bacterial and fungal diseases will overwinter in the soil.

it is not impossible to buy "already infected" plants, and "wind blown" cannot be ruled out in cases.

regardless - there's a age old theory about preventing garden soil from splashing onto tomato foliage.

it's a two pronged thing - by all means prune off the lower leaves/stems - never let them hang down to / touch the soil. never yet met a tomato that would not grow more green stuff on top....

the second is mulch - from the instant you put the plants in the ground - cover any bare soil around the plants - deep - 4-6 inches - out to 2-3 feet.\ when they're small, increase as plant grow / spread.

I also try to rotate their location, and I never compost the tomato "left overs" -
regardless I always get some bacterial/fungal/wilt of some flavor - but it seldom takes out the crop.

[sepeters]

Hendi, I experience a similar problem with my tomato plants in July - August. Keeping the leaves off of the soil definitely helps. Last summer I started using vermicompost tea in the water once a week and as a foliar spray as often as possible. It did not stop or reverse the problem, but it sure did slow it down...for a while anyway.

[JayPoc]

So what about cages? I mulch, keep stuff off the ground, etc. But if last years cages likely have some of the pathogens, be they fungi or bacteria, how can you decontaminate them?

[imafan26]

Humidity is hard to work against. Usually I have to use a preventive spray in that kind of weather. Selective pruning to open up the branches and spacing for air circulation are the only other things to do. Pruning in the heat can be tricky since tomatoes need their leaves to keep from getting sunburn. To bad I can't run a fan on them outside when the winds are calm.

I also try to get varieties with VFNNTA resistance. Unfortunately resistance and taste seem to be inversely related.

[PaulF]

Cages absolutely need to be disinfected. A 10% bleach bath will do the trick. I use a garden sprayer and soak the cage thoroughly. One method I did use worked well was to fill the grandkids wading pool with water and bleach and roll the cages around in the pool. Disinfected both the cages and the wading pool. I just let the cages dry out without rinsing. (I rinse the pool.)

I my opinion, all those resistance letters are meant for commercial tomato growers. In a backyard garden setting, an extra few days of resistance really has no meaning, but to a commercial grower a couple of days means harvest success or failure. A good mulching program to keep soil splash off leaves and perhaps pruning the bottom of plants to keep leaves off the soil and to help with airflow is all that is necessary.

I agree with the flavor assessment of commercial hybrids and home grown heirlooms/Open Pollenated tomatoes. Good growing practices will allow all varieties to be disease resistant.

[hendi_alex]

This year I'm running a bit of an experiment. Lots of volunteer tomato seedlings are cropping up in various beds. I'm lifting the plants and setting them in pots, as part of the reserve pool. I'm wondering if these volunteers might have developed some level of 'native' resistance or may otherwise be a little hardier than the more pampered seedlings, that were forced to start much earlier.

Also, the past week or longer has been overcast and anywhere from very rainy to slight drizzle. Thankfully (I hope) that this has come early in the season while temperatures are still moderate. The overcast rainy conditioned are supposed to last for a few more days. I'm considering a preventive spray near the end of this rainy episode. Perhaps will spray half the plants and leave half alone, to see if there is any difference.

I just hope the sun doesn't pop out and bring summer like temperatures. If the humidity can drop off and the plants can dry out with 70-80 temperatures with a good breeze, likely no harm will be done.

Just in case, I'm still starting fresh rounds of seedlings, and today or tomorrow will gather some cuttings.

[rainbowgardener]

Keep us posted on all the experiments, alex! I do think the humidity, which we can't control, is a major contributing factor, more even than rain. The rain comes and goes and dries out, the humidity is constant. Last year, the drought was so bad, that we even had no humidity, besides no rain. First time I have ever seen deep blue Western style skies in the summer in Cincinnati. Usually the humidity makes it look kind of grayish. It was pretty, but a little freaky. Anyway, it was also the first year I never had any disease issues with my tomatoes. Usually by the end of the season, they are looking quite ragged and so many of the bottom leaves have been pulled off when they started to get septoria, that the plant looks sparse and top heavy. Last year at the end of the season the plants were still lush and deep green and beautiful; I just hated to pull them.

Not that that is any help in figuring out what to do. I certainly don't want to hope for drought!

[gixxerific]

Yes humidity is the killer. Like RBG said rain comes and goes. But humidity is here 24/7. Again as RBG stated last year was disease free for me. Which is very abnormal.

87 % humidity right now. Of course it has been raining for 11 hours straight too.

[hendi_alex]

Well here it is June, just in front of prime tomato disease season. So far just a few plants show light to medium affects of summer blight or what ever the slow yellowing from bottom moving toward the top is. The low level of visible disease is misleading though, as when the conditions get right, it will literally explode, killing a plant in a matter of a few days to two weeks.

Since starting this thread I found an interesting experiment from one of the State ag agencies. They sprayed the tomato vines regularly with copper solutions such as Bordeaux mix and they also used neem oil. The results supported by nice photo illustrations, were pretty convincing. For heirloom, non resistant tomatoes, spraying has almost no effect. At the best it slowed the progression just slightly. For resistant tomatoes however, if they were on a regular spray regimen, still looked green and vigorous late in the season.

My take is that it is a waste of time and money to spray the heirloom varieties. Also, if someone wants late season tomatoes, it is best to have at least some disease resistant varieties that are sprayed regularly before and after rainy periods.

I'm continuing with my succession plan, where tomatoes are constantly kept in a nursery area or two, waiting to serve as replacements when and if needed. I currently have plants as small as three or four inches and as large as two feet in three gallon containers.

My strategy for a steady stream of tomatoes involves spraying with neem oil and perhaps with Bordeaux solution, keeping a steady supply of fresh vigorous young plants developing, planting lots of varieties including some resistant ones, and planting fresh plants in the early fall, timed to give their main crop 2-4 weeks before the first frost. I'm also testing the use of shade cloth which was just put over some plants this week. Last year I noticed that a few plants under shade cloth did much better than most other plants. I'm thinking that the heat of the noon to afternoon sun puts the plants under daily stress and that stress makes the plants more susceptible to disease. Will be interesting to see how the plants that are under 40%-60% shade cloth perform.

One other thought about tomato disease in this area. I've decided that the disease is everywhere around here. There is no such thing as a clean spot in the yard. Even container plants grown in miracle grow potting mix in large 25 gallon containers get the disease when conditions are right. So I'm no longer worrying about trying to decontaminate anything. Just a wast of time IMO. I will continue to spray shears with Clorox when moving from plant to plant doing any pruning. Will also continue to toss any night shade remains outside the yard and garden area. Aside from that, my attitude is that the disease exists, it will take off when conditions are favorable, and any action to keep a steady stream of tomatoes must be in that context.

[gixxerific]

good luck with your experiment.

I also have backups going I was just thinking about dropping more seed just in case, Especially a few special variety's.

[hendi_alex]

I started seeds until about two weeks ago, but the last batch failed to germinate. Probably too hot. At that time I also started taking cuttings from a few plants. The first four have now rooted and are about six inches tall. I'll start new cuttings through the end of June. After that it will most likely be too late for either seeds or cuttings to mature enough to set a crop. We usually get a good crop of tomatoes in the fall, but plants start growing noticeably slower with the cooler temperatures and shorter days of September and October. The 85 days until harvest or whatever packet labels need to be extended when planning for the fall crop.

[Cola82]

I've been wondering about this. I've been pruning yellow branches on the bottom of my tomatoes but noticed just today that all of the leaves on both plants have little yellow spots, like freckles. Since this is my first year growing tomatoes, I wasn't sure what to make of it.

I'm guessing I should expect that at some point in the summer I'll lose them? Is it too late to try spraying them? I've been hesitant to use neem oil on the outside plants because of all my spider bros, but I'd rather have healthy plants.

ETA: just want to add that I've been keeping the barrels with the tomatoes under the awning on our patio, so they only get sun until about noon and no rain hits them. They do still wilt every morning and only perk up when the sun goes behind the house.

[hendi_alex]

If the plant is a highly resistant variety, then the tip growth will most likely continue, but the plant will become much less productive as it looses most of its foliage. If the plant is not highly resistant, then it will likely be dead by mid summer, whether you spray or not.

It is an interesting thing however. You can pinch or snip some tip growth from one of these diseased plants, just above a leaf node. Pinch most leaves off and place the plant in a pot of decent quality potting mix, up to within a couple inches of the tip and keep it constantly moist. The tip will usually take root after a few days, and will start to grow strongly. There will likely be no sign of disease on the plant, and it can serve as a replacement for the parent plant. As the cutting grows and develops however, it will be just as likely to get the disease and its progression, until conditions improve such that temperatures and humidity fall to the point that the disease is no longer very active.

I try to keep many such replacement plants in the nursery area. The young vigorously growing plants are much less susceptible to the disease, therefore can always be ready to move into the ground as replacement plants. Most all will give at least some amount of harvest before becoming overwhelmed by one disease or another.

[Cola82]

Would it be worth taking a cutting of a determinate variety?

I still have a few seeds--I could start a couple extra plants, but I'm guessing it's probably too late for that.

[hendi_alex]

Well there is almost no effort in the experiment. If the cutting takes, then it will have been worth the 'trouble'. My guess is that the determinate will root and grow just as well as an 'indeterminate' but I have not done cuttings from the determinate before so can't say for certain.

[Cola82]

Okay, I spent a lot of time looking at photos of different tomato diseases including southern blight and I'm not super sure what I'm seeing on my plants matches any of them. It's always hard to tell, of course, because all of the photos are usually from very advanced stages of diseases, and written descriptions can be misleading. So I figured I'd just take a bunch of photos of the leaves and ask you guys if this is actually what you're talking about, or if it's something else.







ETA: The first two are one of the upper leaves of the plant, and the third is a leaf from the lowest branches. I've clipped so many of the lower branches and much worse off leaves that this is about as bad as it gets down there now, but I figured you'd get the idea.

[hendi_alex]

First plant to give in to disease, probably will be dead in a weak. Will only get a couple of tomatoes from the vine.



Interesting thing, four nearest neighbors have not signs of disease so far. All four look as good as this plant. The pot to the right contains the diseased plant.



We are in the middle of a rainy period. Today the plants were sprayed with neem and will likely spray them again in the next day or two. Supposed to be very hot following the rain, so I'm afraid my plants may get hit hard with disease during this hot, humid period following so much rain.

[lakngulf]

Good luck with your plants. You always hate to see one bite the dust, but you seem to have the same attitude that I have....Do what you can, but it's gonna happen. I have lost four so far, but the deterioration of the leaves is different.