I know about tomato diseases, and the 2 grafted ones seem to be getting along. I'm an organic grower. So it seems obvious that I need to solarize the soil. I have framed beds, so I can wrap clear plastic over and down them.

But I've never had to do this before. So, how tight does it have to be. Are bungee cords enough or are we talking duct tape? How long does it take? Is Winter to Spring enough or will it take all next Summer? Should I water the soil before covering it or should I want it dry? Just how hot does the soil need to get?

I'm getting by with grocery store cherry tomatoes (the heirlooms are pre-chilled, so tasteless) and it is horrible. The nearest Farmer's Market is 20 miles away and I hate to drive. And they mostly offer hybrids. I can't TELL you how much I want a good un-pre-chilled Cherokee Purple or Brandywine...

I would just build a couple new beds with fresh soil to use for a year during solarization, but outside my enclosed garden, the groundhogs squirrels and other varmints just eat the pre-ripe fruits of anything. I haven't harvested a ripe apple in years, for example.

So, what are the details and time-schedules for solarizing the existing beds in the safe enclosed area?

Hello -
Others will have better and more definitive information but I will share what I remember from reading a research paper written by (I think) a Phd student at Texas A&M.

Clear, heavy plastic; not black or other.
Soil cleared of weeds first and well watered.
Plastic tucked/buried at the edges
Cover the soil for four weeks during the hottest part of the year.
After solarization fresh compost should be worked into the soil to reintroduce beneficial microorganisms which have been killed - solarization is, after all, a non-selective process.

In the case of raised beds I shouldn't think 'wrapping' the sides would have any effect as it is the direct, amplified solar heat on the soil surface and radiating downward that is responsible for the effect.

As I recall it was being tested as a means of minimizing weed germination and growth though they noted that in addition to weeds and weed seeds it also killed bacteria, nematodes, insects (both good and bad), etcetera. Whether it will have an impact on disease from soil-borne bacteria is unclear to me.

Good luck.

The question is simple: why are you so sure you need to disinfect the soil?
If you are having problem with Fusarium, solarization alone is not enough: it's useful only if used in conjuctions with fumigants. Fusarium is difficult to control even with fumigants and if you don't want to use them pretty much the only choice is steam sterilization, followed by covering up the soil (black plastic mulch), and bearing in mind Fusarium can recolonize even fumigated soil very quickly.
If you have problems with root-knot nematodes, the cheapest and most effective cure is to grow cultivars with genetic resistance: the Mi gene is known since the 40's and has been introgressed into tomatoes since the 50's. It's not effective against all RNK species but it's worth a shot.

Here is my understanding of solarization. It is mostly done to reduce weeds in the garden. Solarization will only affect soil to a depth of a few inches, maybe as many as 5 or 6. Soil pathogens on the surface will be killed as will beneficial organisms. The pathogens go much deeper and will quickly migrate back to the surface.

There are better ways to avoid pathogens infesting tomatoes and other plants in the garden. Most importantly a good mulching program so that soil splashing onto plants is avoided. Most pathogens are soil borne. I happen to use layperson of newspaper topped off with several inches of straw but there are many other effective mulching practices. Good garden clean up and watering at the base rather than overhead will help. To me, choosing varieties with so called resistance is not much of an issue. That is for large scale growers not the back yard grower where an extra couple of days will make little difference. Good cultural practices will do much more than solarization.

Hey Yardenman!
So here is what I think is best to do in my experience at home and from what i've heard from other more experienced tomato gardeners. I don't think solarizing will actually solve your problem. In fact, I think it will do more harm to your soil than good because solarizing will inevitably kill all the microbes and organisms in your raised beds. Now while it may sound good, I have pretty bad news. For the most part, all of the most common types of problems that tomatoes get, including blight and wilt viruses and all those, are soil borne. The reason solarizing I don't think will help is because of the fact that they are pretty much anywhere and will make their way into your soil, my soil, and pretty much everyone's soils. I don't think trying to kill the first few inches of soil to kill weeds and harmful bacteria will actually do the job anyways as the bacteria will make their way up anyways.
Instead, I think there is a better and even beneficial way of fixing the problem. To avoid soil borne diseases and weeds, simply add a good organic mulch. It can be a good weed free straw, grass clippings from mowing a lawn, it can sifted or decaying wood chips, etc. Mulch is wonderful. It protects the soil from the sun, it holds moisture, it adds organic matter on top of the soil and adds fluffiness over time, provides a wonderful for bacteria and fungi, including the coveted mycrorhyzhaii fungi...im sure I spelled that wrong lol. And yes, it suppress most if not all weeds if you have enough of it. Plus, if you plant your tomato stems deep, this will allow more roots to grow into the organic matter too.
So i recommend a nice generous mulch a few inches thick. You can use compost, chicken manure, as well. Just cover the ground thick.

Thank you all for the advice. I always thought the way to eliminate tomato pathogens was solarization. I'm glad to not have to do that (I might anyway).

But I still have the problem with tomato-diseases. Allow me to explain my set-up... I have raised framed beds about 12-16" high. The soil is a mixture of old bed soil, and 50/50 topsoil/compost from a local nursery, and some sand. I use only slow-release organic fertilizer in general. It is about 4-6-6.

I grow my own heirloom seedlings to about 12" high and transplant them deep in a 8" wide hole adding some of the fertilizer with crushed eggshells as I backfill, allowing about 4" seedling tops above ground. I've been gardening for 50 years and learned a lot from my organic Grandad. So I kind of assume I know what I'm doing.

BUT, last year the tomatoes struggled and this year, they are doing worse in the same spot (and one I planted in a different bed died too). I've lost 4 of the 12 plants. Yellow leaves from the bottom up.

Last year, I used red plastic mulch (impermiable) and added water jugs with spouts below-ground to keep them wet 2x per week (and of course it rains sometimes). This year I used black permeable fabric, so no watering issues. I water the plants at the surface and in mid-day for drying any dampness on leaves.

I have a moisture-meter to check the moisture at root level and it is "average" most of the time.

I could use more sunlight (tall neighbor trees) but I think that would show a more general plant weakness and some plants are doing just fine. I have 2 grafted tomatoes and they are doing great. I have even been foliar-spraying the tomatoes.

I'm at my wit's ends... What on Earth do I try next? There has to be something I am just not realizing...

Yardenman, I don't know if this will be of any help to you, but for what's it's worth..

for years I struggled with my tomato plants dying an early death from blight? wilt? I never did pin down what exactly the problem was, but it was certainly frustrating. Then, about 4 or 5 years ago, I started growing my tomato plants in a smallish (7' x 15') "high tunnel" type of greenhouse - that first year it was just a few plants in the high tunnel, most of my tomatoes were outside - and amazingly the insiders were completely disease free, despite they were planted in the same garden soil where I had grown diseased tomatoes in the past. That was so amazing that we built a larger (16' x 20') high tunnel, and now all of my tomato plants are grown inside (but planted in the ground, not containers). I water the plants without wetting the leaves and have had essentially no disease whatsoever since 2016 - and as an added bonus (something I just realized this year), have never had a tomato with blossom end rot in all that time, either. The only real problem that I've had is that my large high tunnel really should have more ventilation and some varieties have not done well due to the high temperatures, but overall the plants keep on growing and flowering well past our first frost and pretty much until we get a really hard freeze. Just something you might want to consider trying... best of luck to you!

Forgive my rudeness, but you still haven't told us exactly what the symptoms are.

Some diseases like Stemphylium have very patchy distribution, meaning they are a plague in some area but pretty much unknown elsewhere, but this doesn't mean they can occasionally pop up elsewhere.
In other cases you may not be dealing with diseases, but with phytotoxicities, meaning various forms of poisoning due to abiotic causes, Diagnosing phytotoxicities is generally hard even with the help of an extension/agri laboratory since most agents either don't show up in testing or only cause symptoms under certain conditions.

There's also the possibility you are dealing with some pathogen for which genetic resistance is available (IE root knot nematodes): just remember this doesn't mean "complete immunity" but various degrees of resistance. Some plants may be unaffected, some may show only mild symptoms but others still may succumb late in the season. Resistance genes usually have different grades of expression, which may be further exacerbated by growing conditions.

If you are dealing with a phytotoxicity brought about by mineral salts or nitrogen burn you can solarize and fumigate the soil as much as you can but you won't obtain any result.
Give us something more to work on.