If your tomatoes are looking a little less than healthy as they begin to ripen, it could be an early blight to blame.
That’s the bad news. The good news? If you’re looking for tips on how to eradicate early blight in your garden, you’ve come to the right place.
Early blight can appear early on in the tomato plant’s life cycle, or it can rear its ugly head later on.
Whatever the case may be – and whatever stage you may find yourself in – take solace in the fact that early blight can be addressed. Follow these tips to get rid of it for good.
Early blight (Alternaria tomatophila and Alternaria solani) is a disease that can appear early on in the life cycle of the tomato, causing seedling damping off (also known as rot) as well as later on.
If it occurs later on in a tomato plant’s life cycle, it can cause issues such as leaf blight, stem cankers, and blakc fruit rot.
The most telltale sign of early blight is when you detect leaves with circular lesions that are up to half an inch in diameter each. These usually have darker concentric circles inside of them.
Although symptoms can appear later in the life cycle of a tomato, if you notice systems primarily on plants that are just about to be harvested, this is probably late blight.
This is caused by a different pathogen – Phytophthora infestans. Incidentally, this is the same pathogen responsible for causing the Irish Potato Famine.
Late blight kills tomatoes slowly, often more slowly than potatoes, but it will totally annihilate your fruits.
With early blight, you’ll notice that small dark spots first form on older foliage that is growing close to the ground. As time goes on, these spots will become rounder, larger, and browner, often causing leaves to turn brown or fall off the plant.
Sometimes it is seedling stems that are affected. This usually occurs right at or above the soil line, with the stem becoming sunken, dry, and brown. Sometimes the seedling will wilt and die entirely.
The fruit can be affected at any stage, causing leathery black fruit spots, often near the stme, with infected fruits falling from the plant.
If you aren’t sure whether your plants have early or late blight, don’t worry – the end result is the same (your tomatoes will die and your yields will suffer) and many of the treatments are also the same.
Symptoms can appear very quickly – in as little as four or five days – and spores are spread easily. These can move via the wind, human contact, or cultivation equipment, making it easy for gardens to be continuously reinfected.
Early blight is most common when temperatures are warm (between 60 and 86 degrees Fahrenheit) and wet (90% humidity or greater is the ideal breeding ground for this disease).
There are a few ways you can prevent and treat blight disease. Here are some of the best.
Even if you’ve never had a problem with blight in the past, it’s a good idea to get in the habit of rotating your crops. Not only does good crop rotation prevent blight, but it can keep a whole host of other pests and diseases at bay, too.
Don’t plant your tomatoes in the same spot where tomatoes or related plants (such as eggplant, potatoes, and peppers) were grown within the last three years.
Early blight diseases can overwinter in infected plant debris and in the soil in most places, even those with harsh winter weather.
Keeping the garden as weed-free as possible is another step you can take in your fight against blight. Remove any weedy relatives of tomatoes, like ground cherries and nightshade plants.
Toss these when you weed instead of composting them – that way, you don’t have to worry about accidentally reintroducing disease to your garden.
Only plant healthy tomatoes in your garden. These should be grown from seed or purchased from a reliable grower – after all, nothing is worse than unknowingly planting disease plants!
You might also consider planting tomatoes that are blight-resistant. Over the years, researchers have isolated genetics that make tomatoes more resistant to blight. Some good varieties to consider growing, especially if you have had an issue with blight in the past, include:
- Iron Lady
- Defiant PhR
- Mountain Magic
- Mountain Supreme
- Plum Regal Hybrid
…the list goes on and on, but there are plenty of varieties you can consider growing.
Watch your watering. As a general rule of thumb, it’s always a better idea to water plants from below than from above.
If you water from above you risk soil splashing up onto the plants and spreading spores and diseases to them. Water from below, using drip irrigation systems or soaker hoses, and the risk is much lower.
Of course, you can’t eliminate the splashing water risk entirely, since there will always be natural rainfall to contend with, but it’s something that can help.
Be diligent about fertilizing your plants – but not too diligent! Avoid over-fertilizing with potassium and try to maintain adequate levels of phosphorus and nitrogen. This can reduce your risk of disease.
Compost tea is one specific type of fertilizer that can be hugely helpful when preventing and fighting early blight.
Combine one part of aged compost (it should be at least five months old) with six parts of water. Put it in a covered container and let it steep at temperatures between 60-and 70-degrees Fahrenheit (15 to 21 Celsius). Stir once a day.
After six days of steeping, pour it through cheesecloth. The final liquid can be used as a foliar spray.
When plants are wet, be it from irrigation, rainfall, or dew, do your best to avoid working with them or around them. This can greatly reduce the risk of spreading disease.
Again, avoid overhead irrigation to help keep the foliage dry.
Stake your plants to help reduce contact between the leaves and the spore-contaminated soil. This will also increase airflow and make it easier for the plants to dry. If you don’t want to stake, using tomato cages or trellises can also be effective.
Mulching can be highly beneficial when it comes to controlling humidity in the soil. It can also create a barrier between contaminated leaves and soil.
Use an organic mulch or a synthetic one like plastic, which will help keep soil conditions consistent and various diseases at bay.
In the fall, after you’ve finished harvesting all of your plants, take the time to clean up the garden. Remove or bury the infected plants to reduce the likelihood that the pathogen will survive next year.
If you’re growing tomatoes in a greenhouse, you have the benefit of more control when it comes to the conditions for your tomatoes. Take advantage of this – you can dramatically reduce the likelihood of early blight by using UV-absorbing vinyl film to cover your greenhouse.
Do your best to plant your tomatoes in soil that is well-draining and well-aerated. Amend before planting with compost or other amendments.
This will help keep your plants strong and vigorous while giving the roots the space they need in the soil to find oxygen, nutrients, and water (though not too much water).
Pruning is helpful both in preventing early blight as well as in controlling its spread. It can remove disease portions of the plant and open up the plants for better airflow, creating a win-win situation.
Choose several different types of tomatoes to plant and plant them all at different times. If you plant tomatoes so that they are always at different stages of growth, you won’t have to worry quite as much about blight wiping out your entire crop.
Early blight is a disease that is much more likely to affect varieties of tomatoes that mature sooner in the season, so keep that in mind when selecting options to plant.
If you’ve already noticed blight in the garden, it’s not too late to take action. Here are some remedies you can try.
The first thing you should do if you notice any plants with blight is to get rid of live plants that are infected. This will help remove some of the disease from the soil and prevent it from jumping to nearby plants.
Dispose of infected plants in the trash. Do not attempt to compost them – even if your compost gets very hot, there’s not a strong chance that the disease will be killed.
Early blight can be controlled with several different types of fungicides. However, it’s important to note that some tomatoes are no longer sensitive to certain fungicides, so it may take some trial and error to find the right chemical.
Common products used to treat early blight include active ingredients like penthiopyrad, boscalid, pyraclostrobin, fenamidone, azoxystrobin, and cymoxanil, to name a few.
Soil solarization is a process you can take advantage of to get rid of early blight in the garden. This removes fungal spores and other harmful microorganisms in the soil.
To do it, purchase a plastic sheet (like the kind you might use for painting as a drop cloth to protect your floors) from the hardware store. Measure the garden and cut the plastic to cover it with 12-inch margins on each side.
Using a heat-tolerant glue, roll up the plastic pieces along the broadest edges of your garden. Remove all debris, including fallen leaves and dead plants. Rake the garden.
Water thoroughly, soaking the soil. Make sure the soil remains level while you water. Then, unroll the plastic so it covers the garden. Use large objects like rocks to tack down the edges and remove air pockets.
Secure all the sides, making sure there’s no space for air to creep in. You should leave the plastic out for at least three weeks. If you can, do this in warm weather so it really kills the organisms in the soil.
Remove the plastic and you should be good to go!
Take the time to sanitize all of your equipment, particularly if you’re working with plants that you know for sure have early blight. Garden tools should be sanitized between each season of use to make sure they do not spread disease.
Disinfect them with bleach and water after each use and do a deeper clean at the end of each growing season.
This technique might not work on more advanced cases of early blight, but you might be able to use it as the first line of defense (especially if you’d like to avoid having to use chemicals like fungicides on your plants).
Make a mixture containing a quart of warm water and a teaspoon of baking soda. You can also add a drop or two of liquid dish soap – this last addition will help the solution stick to the plant without damaging it.
Pour the mixture into a spray bottle and mix thoroughly. Then, apply it to the plant. Avoid applying the solution in direct sunlight, as it can burn the plant, and don’t apply it more than once or twice.
Although baking soda is perfectly safe to use, it is strong and can damage your plants in excess quantities.
Deeply till the garden in the fall. Disrupting the soil will prevent the spores from having an undisturbed place to rest over the winter months.
It doesn’t totally eliminate the likelihood of infection, but it can reduce it.
Now that you have a few tips in your toolbox to help you fight early blight, you might be wondering, “how long am I going to have to deal with this problem in my garden?”
The bad news is that early blight can endure for about three to four years in the soil. Because of this, it’s a good idea to find a new spot for your tomatoes if you’re suffering from the disease.
Ultimately, though, you can be victorious. Just stick with it!
Rebekah is a high-school English teacher n New York, where she lives on a 22 acre homestead. She raises and grows chickens, bees, and veggies such as zucchini (among other things).