I often run across people asking question about growing tomatoes, and there is a lot of confusion and incorrect info out there. I’m going to try and address a few of these issues as best as I possibly can here.
COMMON FUNGAL DISEASES
There are TWO types of Blight, EARLY and LATE.
I wish the names were completely different so there wouldn’t be so much confusion about them. When discussing Blight, it is best to make sure to say EARLY or LATE.
They must be treated very differently.
(Clicking on the Fungal Disease name will bring up a picture.)
LATE BLIGHT is a devastating disease. Late blight looks moldy with spores and black lesions. Once it takes hold, it will spread and ruin a garden very fast. It is not good! Everything dies quickly. Late blight occurs when there is way too much moisture and it is cool out. so in a hot climate you normally would not see late blight until late in the year hence the name. But it can occur at any time like it did in the north east a couple years ago because summer was unusually cool and rainy. If caught very very early, and the diseased tissue is bagged and removed, you might get lucky and not have it spread especially if the weather takes a quick turn for the better. Usually though the spores have taken hold and the plants go down fast. It is not curable most of the time, spraying won’t help. Cornell has a page with excellent photos, Click Here.
GREY MOLD is another fungal disease which is sometimes MISTAKEN for LATE Blight. It also causes fuzzy mold. It happens though when it is warm and moist instead of cold and moist.
EARLY BLIGHT causes oyster shell/bull’s eye/concentric ring looking spots on the leaves, and they develop a yellow halo. The whole leaves eventually turn completely yellow and die. Vigorous plants can keep on going with it, but if conditions are very good for Early blight to be happy, even vigorous plants will have trouble. Warm humid/wet conditions are what makes Early Blight take hold. There are fungicides like daconil and copper that help control it.
SEPTORIA is another fungal problem similar to Early blight. It causes small dark spots that develop yellow around them like you have in your close up photo of the leaf. It is also a warm humid/wet weather problem. Spraying with fungicides also works for Septoria.
These foliage problems listed above are the MOST COMMON problems of the home gardener. BOTH heirlooms and hybrids are susceptible to them.
There are breeders working on hybrids that are resistant to fungal issues, but most all tomatoes have issues with them.
People often buy hybrids thinking they will have more resistance to the fungal diseases in their garden. This is an OLD hybrid MYTH that won’t die. Hybrids will get the fungal diseases just the same as the heirlooms.
Hybrids can have disease resistance, but it is to OTHER problems NOT fungal ones.
The disease that hybrids are resistant to, along with their letter codes, are listed here:
A – Alternaria stem canker
F – Fusarium wilt
FF – Fusarium, races 1 and 2
FFF – Fusarium, races 1, 2, and 3
N – Nematodes
St – Stemphylium gray leaf spot
T – Tobacco mosaic virus
V – Verticillium wilt
TSWV – Tomato spotted wilt virus
Many of us in NORTHERN gardens will NEVER see these non-fungal diseases.
Some SOUTHERN gardeners DO NEED to get hybrids with resistance to certain problems on the list, like I know some Florida gardeners have Nematode problems. So know your area and what diseases maybe a problem.
Also SOME SOIL BORN problems can be alleviated by growing in planters.
Also be aware that HERBICIDE DAMAGE can mimic disease!
BLOSSOM END ROT in Tomatoes
This is when the plants look fine, but the bottom of the fruit is all black. The fruit is no good. It caused by inadequate calcium absorption into the plant. Uneven watering, temperature, and cultivar play into this.
- ROMA type tomatoes get it more oftenfrom genetic predisposition.
- EARLY fruit is more susceptible to it from either cooler temps or the temp swings early seasons can have.
- Plants in CONTAINERS often get it at a higher rate than in ground plants since soil can go from wet to dry easily if pots are not of proper size for root growth.
- Wide swings in WATER patterns ie very dry, tons of rain, very dry will also cause it.
99.99% of the time, the soil is NOT deficient in calcium. Buying “cures” for it are a waste of money!
To reduce the frequency of this problem, control watering as much as you can. (Sometimes Mother Nature is crazy and there isn’t much you can do.)
If a certain cultivar gives you problems when the other ones are fine, don’t plant that one again. Another variety similar to it may perform much better for you.
You do not have to prune tomato plants. I never prune them (except for accidents! lol.) Pruning will not give you more fruit. It may give you bigger fruit. Any plant grown for size whether a tomato, pumpkin, dahlia, etc. will need pruning. If you are having space or disease issues, you may need to prune, but you do not have to do any pruning to have a great tomato crop.
Here’s a LINK (CLICK HERE) to my tomato expert friend Craig Lehoullier’s article and video about pruning. He does show the correct way to do it in the video.
Ok, I get asked the following (or a close version of it) quite often. So I figured I would repost a forum question that I replied to here.
Need: simple explanation. heirloom, hybrid, genetically altered. I think I understand these three things fairly well but I fail miserably when trying to explain them… Is organically grown seed really important?
In my opinion, no organic seed isn’t that important (unless you want to sell veggies and be certified organic.) Growing organically is. Adding lots of chemicals while gardening is not good for anyone.
You, as a home gardener, can not buy GMO (Genetically Modified Organism) seed. Only commercial farmers can, and when they do, they have to sign legal waivers and stuff. So your friend does not need to worry about buying GMO seed. Unfortunately many companies advertise on people’s fears and you will see “No GMO Seed Sold Here” or something similar. Well of course there’s no GMOs because you can’t buy them as a home gardener! This of course does not mean things will change in the future.
Hybrid seed is the F1 seed of a cross. F1 means first generation. In the first generation, all the babies will be identical. Subsequent generations from saved seed will not come true( plants will vary. How much depends upon the parents used to create the hybrid.) There is nothing wrong with Hybrid/F1 seed. It is done the old fashion way like the bees do it (there’s not GMO stuff going on), but it is done in a more controlled environment. So hybrid seed cost more for the work involved, and you can not save seed without having the seedlings vary. So why would you want to grow a hybrid? Well hybrids may have something you like like resistance to a certain disease, or some are very good like Sungold tomato. It is an amazing cherry tomato, and it hasn’t been duplicated in OP form.
OP means Open Pollinated. These are plants that can grow true from seed. Some OPs are heirlooms some are not. Heirlooms just designates that a variety has been around a long time. Most would agree a heirloom has been around for about 100 years. So they are OPs that have stood the test of time. The best OPs of today might someday become well loved heirlooms.
I hope that all makes sense. Please tell your friend that this answer came from a person who owns a seed company and knows what they are talking about.
Also tell her to be careful there are companies out there who advertise Organic and they are NOT certified organic. One in particular sells overpriced tomato seeds. So you do need to be watch for people who are pretty much ripping people off. There are well priced certified organic companies out there. Or there are people like me who do organic garden and state that as a fact that I am not certified. And also that many seeds I sell from other growers are certified, and if the person really needs to know, just ask.
Hope this helps,
To read more in depth info about this, CLICK HERE.
(This is an ongoing page. More info will be added as time allows.)