I garden in Maryland Zone 7. There are two fungal diseases that attack my tomato plants and they are Leaf Spot and Early Blight Each garden zone has its own set of issues with plant diseases and each zone varies for when the diseases may arrive.
Leaf Spot comes to my area in the late April and through May when the temperatures get around 70 degrees and the rains come. Prolonged wet days and the right temperature brings Leaf Spot to my garden tomatoes. Three years ago it was really bad in my area and that is when I learned how to best manage it. I have not had issue with it for several years.
Leaf Spot is a fungus that reproduces through spores. The key to effectively managing this disease and other fungal diseases is to create an 'unhospitable' tomato leaf surface for the spores. By treating the tomato leaves you make it more difficult for the spores to take hold and reproduce. This doesn't always prevent the disease from taking hold on your tomatoes (it might) but it does greatly slow the progression of the disease down. It can even stop the progression.
The best way to stop Leaf Spot is through preventative spraying. That is, start spraying before the disease comes to your garden. Remember this varies from gardening zone to gardening zone. I start spraying about now as part of my prevention plan.
Baking soda spray reduces the acidity level on the tomato leaf or raises the PH level on the leaf. This change in the PH level, reduction of acidity, is NOT what the Leaf Spot spores want to reproduce. They want a normal tomato leaf surface. The baking soda spray, by changing the PH level of the tomato leaf, prevents and/or interrupts spore reproduction.
The baking soda is only effective while it is on the leaf. It really needs to be reapplied after every heavy rain and about every week to be most effective. You can find slightly varying baking soda spray recipes on the internet. Use which ever one you are most comfortable with.
To make a baking soda foliar spray you mix 1-2 tablespoons of baking soda to 1 gallon of water. The concentration varies based on your garden zone, temperature and sun intensity. Always test spray any new foliar spray on a few leaves and wait 24-48 hours to see if any damage occurs.
In my area, from experience, I can use 2 tablespoons of baking soda per gallon up until late June or early July without concern. Last year I used this concentration when the high 90 degree temperatures hit with full sun. The same spray that worked fine for April, May and June... burned many of the plants leaves when used in early July. When the higher temperatures come to my zone, I change to 1 tablespoon of baking soda or use wettable sulfur spray.
Wettable sulfur does the same thing to the fungus spores but does it by raising acidity levels of the leaves or reducing the PH level of the leaves. It is the opposite to baking soda. I also spray in the morning or evening when the heat comes.
- 1-2 tablespoons of baking soda per gallon of water
- Remember to test spray your leaves first
- Be aware of temperature and sun intensity
- Spray after each heavy rain or at least 1x weekly
- The spray interrupts spore reproduction
To treat your tomatoes, all you do is quickly soak the top and undersides of the leaves. The video covers this information and demonstrates how to spray your tomatoes.
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