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Tomato Blight Problem Solutions

Troy Brooks



Tomato Bligh – The Signs, Symptoms And Preventive Measures

There is a common mistake that is made by new or inexperienced gardeners who practice seed saving and that mistake is collecting or saving seeds from tomatoes affected with Tomato Blight. We save Heirloom Seeds for their genetics. That means we want to save the best and the brightest from our gardens and you really have to pay special attention to fruits like tomatoes and Tomato Blight. It’s important for gardeners to be aware of this disease so they can act quickly. Unfortunately, there’s no silver bullet for controlling this disease. The key is to plant wisely, be prepared, be alert, and learn to distinguish late blight from other common diseases. Make sure you know what late blight looks like. Two other diseases, early blight and septoria leaf spot, are similar but unlikely to kill your plant, and drought-stressed plants can show similar symptoms.

Let me start off by saying that this disease named Tomato Blight is caused by a fungus named Phytophthora infestans. Tomato blight thrives in a humid or moist environment. It is a fungus that is common on outdoor grown tomatoes as well as potatoes, especially those that are grown in late summer. Growing tomatoes in a greenhouse, it might offer some limited protection from Tomato Blight, but you still have to watch out for any fungus/disease outbreak in your garden.

Blight’s Life cycle

The fungus that cause Tomato Blight can survive the winter. As I previously mentioned, it can also be transmitted from infected saved tomato seeds. Plants growing from these produce fungal spores which are spread on the wind. The initial infection may come from a local source, such as your neighbor gardens, local farming crop, a garden rubbish dump that wasn’t composted, or the spores may be blown in from many miles away. Spores can only develop and infect your tomato plants if they land on wet foliage or fruit. I’ll discuss ways to prevent the spreading of blight later on. Suffice it to say that this disease can spread very rapidly throughout the garden when temperatures are above 50°F and humidity is over 75% for two days or more.

To prevent this disease from developing, it is important to water tomatoes at the lower stems, i.e. their base, and NOT on their leaves. Try using soaker hoses or drip irrigation for watering tomatoes. Try to keep the plant leaves dry as much as you can, especially during watering times. Water your tomato plants early in the morning and not late in the evening. This will help to reduce the long periods of moisture left on the foliage, which encourages blight. Mulch will reduce the amount of watering needed as well as control the growth of unwanted weeds. Try to avoid brushing past tomato plants when they are wet, doing so increases the likelihood of spreading any infection. When you are watering your plants use this time to check for signs of blight. If you see any infected leaves remove them as soon as you notice them. Be careful not to spread the fungus to other nearby plants. You can compost any leaves that have been effected with blight effectively, as the fungus is not known to survive the composting processing. However, just in case you are still wary of composting blight, make sure your compost bin(s) are not in the vicinity of your garden area and I would suggest covering the bins as well.

Tomato blight infection will occur during a period of warm, moist weather and it tends to escalate during the mid to late summer growing season. As I mentioned, the wind can easily carry the fungus spores and this helps spread the disease very quickly. A high humidity environment can easily infect, damage, and destroy a whole garden if the conditions remain warm and moist. If you live in a high humidity area I would strongly advise growing tomato varies that have short growing seasons. This will allow you to harvest fruit before blight usually strikes.

Those of you who have followed my writings know that I am a proponent of Heirloom Seeds. I only sell Heirloom Seeds because I believe that they are wholesome, excellent quality, clean and, of course, Non-GM (Genetically Modified), the list can go on; however, there are some cases where Hybrid seeds have their place and if your growing environment is conducive to blight then a good hybrid tomato just might be required. There are a few varieties on the market that are said to be resistant to blight – Ferline and Legend for example. They are worth trying, but may only delay the infection rather than ensuring a healthy crop. Some so-called resistant varieties can resist some strains of the fungus and not others, so their performance may vary depending on the strains of blight around.

Symptoms of blight

The symptoms of blight can occur in three (3) places on your tomato plants. (1) foliage, (2) stems and (3) the fruit itself.

Often times the very early signs of blight are easily missed. Not all plants are affected at the same time. Once again, I refer back to the fact that if weather remains warm and damp, this disease will rapidly spread, and in a severe way, attack the plant foliage and may even kill off the plants in a few days. Foliage and stems will show a dark brown/or blackish round patches, often surrounded by a pale yellow halo, that quickly spread to rot the whole plant leaf. If you take a look at the underside of the infected plant’s leaf you may also notice white coating of spores. Dark streaks and spots may also have or start to develop on infected stems. These tend to become pronounced in moist conditions, particularly at night. Again this another reason why I don’t recommend watering your tomato plants at night as it fosters the environment of spreading blight.

Fruits showing symptoms are not pleasant to eat and will not ripen or store, as the fungus will rapidly spread through the fruit even after it has been harvested. Tomatoes that haven’t ripened yet will, of course, be green and will have dark markings developing on fruit. Mature or ripened tomato fruit will have a more distinguished dryish brown rot, which even may appear a few days after picking. A whitish-gray mold may accompany this. Have no fear, the tomato blight fungus is not poisonous to humans, it is fine to eat any ripe tomatoes not visibly affected by the fungal blight.


Earlier I suggested composting the leaves and stems of plants affected by blight. In my opinion and extensive research I am confident that you can safely add the leaves and stems to your compost bin. The fungus will not survive in dead plant material. However, under no circumstance should you compost the blighted fruit, as the fungal spores can survive in the tomato seeds which in term will grow and reproduce next spring, carrying blight onto your new crops. Yes, blight can survive in the seeds of tomato throughout the winter season in general. Either bury deeply the blighted fruit two feet deep or put in a wrapped garbage bag for disposal. Alternatively, take all affected plants to the local recycling center. These centers compost on a very large scale, thus generating high temperatures which will kill the disease.

In closing I will say this:  Unlike Early blight or Septoria leaf spot, Late blight, on the other hand, kills plants outright, and it is highly contagious. Its occurrence in your garden can affect other gardens and farms due to the wind-dispersed spores. Once a plant is infected, it must be destroyed as outlined above.

As always-Happy gardening!


The post "Tomato Blight Problem Solutions" appeared first on Brink of Freedom.


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Guest Carolyn Lundberg


We planted 98 tomato plants and the entire crop got the blight. Leaves died from bottom up and the fruit had small dark spots. We do farmers market and for the most part our tomatoes weren’t good enough to sell. We have had a lot of rain and humidity so this probably contributed to the cause. What should we do this fall when plants die? Rake up plants and burn them ?

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Just now, Guest Carolyn Lundberg said:

We planted 98 tomato plants and the entire crop got the blight. Leaves died from bottom up and the fruit had small dark spots. We do farmers market and for the most part our tomatoes weren’t good enough to sell. We have had a lot of rain and humidity so this probably contributed to the cause. What should we do this fall when plants die? Rake up plants and burn them ?

Carolyn, you should burn them and do not put them in the compost UNLESS you are using a HOT compost method like the Berkey method. If you can not guarantee this, just burn the dead plants and DON”T plant tomatoes in that area for 2-3 years.

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