Anyone who grows tomato plants will know how quickly tomato blight can destroy plants in the garden.
It can be challenging to treat infected plants with multiple tomato blight types once the infection has set in.
The cause of early tomato blight comes from two different fungal diseases. The first attacks the oldest leaves but soon spreads to the stems and eventually the fruit.
It quickly kills seedlings but can also destroy full-grown varieties of tomatoes if not treated quickly.
Meanwhile, late blight is a fast and deadly mold. It first resembles water spots but quickly rots the leaves and stems as it spreads. It even manages to grow on infected tomatoes that are improperly stored.
Anyone who’s used neem oil to combat plant problems in the past knows it can also kill some fungi and bacteria.
You might be encouraged to try it out on tomato blight, but will it work against some or all forms of leaf blight?
Does Neem Oil Help Stop Tomato Blight?
The sad news is that neem oil can’t stop tomato blight on its own.
However, the good news is you can use it to help prevent the onset of both early tomato blight and late tomato blight, and it may even kill the blight in its earliest stages of infection.
How Neem Oil Works to Prevent Infections
When used as a preventative, neem foliar sprays can often kill fungal spores that have landed on the plant’s surface. Soil soaks or drenches can trigger an immune response to fight off an infection that breaks through the plant’s surface.
Both remedies require one tablespoon of pure castile soap per gallon of water to act as an emulsifier.
Neem soil soaks include two tablespoons of 100% percent cold-pressed raw neem oil, while the foliar spray uses four tablespoons of clarified hydrophobic neem oil.
Pour 2 to 4 cups of your soil soak over the roots, which will then absorb the primary active chemical, Azadirachtin, turning it into a systemic insecticide for up to 22 days.
It won’t affect surface infections, but the Azadirachtin will attack fungal infections once they break the plant’s surface.
Meanwhile, thoroughly soaking every part of the plant with the foliar spray at both dusk and dawn will allow it to attack the surface fungus, although the oil will only last for up to an hour.
Why Neem Oil Won’t Stop an Advanced Infection
The active element of raw neem oil, Azadirachtin, isn’t present in clarified neem oil and is the most potent of five active chemicals.
The raw oil’s ability to jumpstart the plant’s immune response allows the plant to fight off the infection but doesn’t attack the fungus itself.
Meanwhile, the clarified oil can kill some surface spores but cannot kill an established infection that has expanded under the plant’s surface.
As infection spreads, the oil’s benefits become less effective, and it becomes necessary to bring in more potent chemicals.
However, the qualities that make neem oil highly effective against a handful of fungi may sometimes prove just enough to stop tomato blight when it first infects the plant.