Tomato blight is one of several diseases caused by fungal infections in tomatoes.
The main types are early and late blight.
The fungus that cause blight move quickly once they set in and can quickly devastate an entire crop.
Most blights are controllable but the best way to prevent crop loss from blights is to stop them from happening in the first place.
This is a short guide on how to identify and treat blight and also how to prevent it from happening in the first place.
Conditions That Cause Blight
- Excessive moisture on leaves
- Chilly weather (stresses plants and makes plants damp)
- Stressed plants
- Other infestations can cause damage that lets blight in
- Early vs Late blight
Early and late blight are quite similar in their appearance but are caused by different fungi and affect your plants differently.
Plants with late blight should be pulled-up and destroyed and your must plant late blight resistant varieties next season.
Early blight can be treated if caught soon enough by following the advice about treating blight in this article.
If it is too advanced or not responding to treatment, the plants should be destroyed as well.
Below is how to tell early and late blight apart.
- A few spots per leaf that can have rings and tan centers
- Dark and sunken spots on the fruits near where the stem attaches
- Dark and sunken spots near the soil line
- Small pale green spots on leaf edges that spread and turn black. If it is humid fuzz can appear on the underside of the affected leaves
- Brown and rough spots appear on green fruits and possibly white mold
Black or brown spots that spread anywhere on the stem
Tomato blights usually start in the leaves and at first spread slowly.
At this stage you can carefully cut away the damaged leaves and discard them (see below for discarding blight infected material).
Be sure to cut well into healthy tissue and clean your tools between plants in order to make sure you do not spread it.
Trimmings should be burnt or buried deep to kill the spores.
Only compost infected material if you compost in a way that gets hot enough to kill the spores.
Since blight is a fungus it can be treated with fungicides. There are several chemical fungicides available for sale.
They are all affective just make sure it is one that is listed for use for tomato blight.
There are many natural products that can help treat blights as well.
Cinnamon has been shown to have antifungal properties and sprinkling it around the base of plants could help keep blights at bay.
Research has also shown that tea tree oil and neem oil are antifungal so a diluted spray of them could also help prevent blight or even treat early blight.
Providing the right conditions
Tomatoes are plants that like lots of sun and heat.
Making sure your plants are healthy and are getting what they need, they will be less susceptible to blight.
If growing your tomatoes in a greenhouse, make sure they receive proper air circulation and movement.
If you are worried about your transplants, using a small fan to move air around your growing space can help a lot.
Trimming and Staking
Keeping your tomato plants trimmed can help prevent blights from occurring.
Remove lower leaves near the soil and make sure you cage or stake the plants to keep them up off the ground.
You can also remove excess side shoots and competing branches to ensure better drying of the leaves and stems.
Blight Resistant Varieties
If your plants are outside and you live in a climate that is often wet and chilly, you cannot always make sure your tomatoes dry.
However, what you can do is choose the right varieties for your climate.
There are several blight resistant tomato varieties that have been bred.
Ask at your local nursery for blight resistant varieties or make sure you do your research when ordering seeds.
Below is a short list of some of the most popular blight resistant varieties.
Interestingly enough, many of the varieties resistant to both types of blight are heirlooms and often breeders look to them to breed resistance into new lines.
- Black Krim
- Red Currant
- Matts Wild Cherry
- Yellow Pear
- Iron Lady
- Big Beef