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How to treat blight on tomatoes


Tomato Blight Treatment and Prevention Tips

While tomatoes tend to thrive in home gardens, they can sometimes be plagued by disease.

Three different types of blight may strike – early, late, and Septoria blight.

What’s a poor gardener to do?

By keeping a close eye on your plants, and starting treatment as soon as possible if you detect one of these insidious diseases, there may be hope for your crop!

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This guide will show you how to distinguish between these diseases, prevent them, and treat the infection.

Here’s what’s ahead in this article:

What You’ll Learn

A Rundown of the Culprits

There are three types of blight that affect tomato plants. Spots on the leaves are the first indication of each of these infections. However, they all have their quirks that allow you to distinguish between them.

Symptoms of early blight.

Two are caused by fungi – early blight (Alternaria solani) and Septoria blight, aka Septoria leaf spot (Septoria lycopersici).

The third – late blight (Phytophthora infestans) – was considered a fungus for 200 years. However, it is now known as a water mold (or oomycete, to be technical).

This organism is what caused the Irish potato famine, forever altering Irish and American history.

Late blight.

Alternaria and Septoria can devastate your crop at home, while late blight is an extremely serious infection that can decimate whole tomato fields.

Late blight is such a menace that you are advised to inform your county extension agent if you find it in your garden.

Read more about identifying late blight here.

Early blight and Septoria are often confused, since each of these infections causes the leaves to yellow and die. And both of these infections start on the lower leaves.

However, it is possible to tell them apart. Here’s how:

  1. Alternaria produces lesions with concentric rings that can also affect the fruit. They appear on the lower leaves first.
  2. Septoria leaf lesions, on the other hand, usually present as numerous tiny brown spots that grow and spread.
  3. Advanced Septoria leaf lesions contain dark colored fruiting bodies that look like grains of pepper. Alternaria does not produce any comparable structures.
  4. The lesions of late blight look different from those caused by fungi. They start out as little spots that look like they are soaked with water before spreading into large purple-brown blotches that appear oily.
  5. This water mold can also infect the fruit in cases of late blight, typically starting on the shoulders.

Check out our in-depth guides to learn more about early blight, and Septoria leaf spot.

Prevention

Prevention is your best bet in the battle against all of these diseases, and in some cases you can nip them in the bud (or leaves, or fruit…).

While these diseases are all caused by different types of microbes, there are common steps that you may employ to prevent infection.

Plan Your Garden

Before you start planting, plan the layout of your garden with the help of your gardening journal.

Locate your tomato plants away from areas where you want to grow potatoes or other nightshades.

Check your seed packets to establish mature sizes of the varieties you are growing. This allows you to ensure adequate spacing between plants, to prevent the spread of disease.

Grow Resistant Varieties

When choosing your plants, particularly if you know blight has been a problem in the past, choosing to grow resistant varieties is recommended. Information about resistance to different types of disease is typically included in tomato cultivar descriptions.

Resistance to early blight is usually labeled “EB” on tomato seed packets.

Keep in mind that resistance is not the same thing as immunity. Tomato plants that are resistant to early blight can sometimes contract the disease anyway.

Resistance to late blight is more difficult for plant breeders to select for, since the water molds mutate quickly and have been able to overcome resistance in the past.

‘Magic Mountain’

However, the cherry tomato cultivar ‘Magic Mountain,’ available from Burpee, is resistant to both early and late blight.

‘Iron Lady’ and ‘Defiant’ are two cultivars that are resistant to early, late, and Septoria blight.

Though it is not quite at the level of being resistant, the ‘Sweetheart of the Patio’ cultivar is tolerant of late blight, and it’s well-suited to growing in containers.

You can read more about this variety and find out where to purchase seeds in our roundup of the best cherry tomatoes to plant in your garden.

Stake Your Plants

Promoting good airflow will also help to reduce the levels of moisture in the interior of the plant. Staking your plants prevents fruit and foliage from coming in contact with the ground.

Check out our guide to learn more about using the Florida weave to support tomato plants.

Fertilize

Ideally you should test your soil before you plant, to make sure the pH is between 6.5 and 7.5, and to determine whether there are any nutrient deficiencies.

At this time, before your seeds or transplants are in the ground, you should amend your soil accordingly.

After that, don’t fertilize your tomato plants again when they are young. Wait until they are well established and blooming before you fertilize again.

Fertilizers with an NPK ratio of 5-20-5 or 4-12-4, with the highest level of phosphorus in comparison to the amounts of nitrogen and potassium, are good choices.

If you need to add nitrogen, on the basis of your soil test results, also apply calcium nitrate at the same time. This will help to avoid blossom-end rot.

Do not add urea or ammonia as nitrogen fertilizers, as tomato plants are very sensitive to ammonium toxicity. This can result in yellowing of the leaves and poor root development.

Remove Weeds

Members of the nightshade family serve as hosts for all of these diseases. Such beloved crops as tomatoes, potatoes, and eggplant are all members of this family.

It also includes common weeds like nightshade and jimsonweed, as well as ground cherry.

All of these types of plants can harbor the pathogens, so be vigilant, and purge them from your garden! This includes volunteer tomato plants as well.

Irrigate at Ground Level

Watering your plants from above can invite infection. This is particularly true in the case of sprinkler irrigation, but even using a watering can can be an unhealthy practice if water is showered onto the foliage.

Instead, use a soaker hose to provide drip irrigation at the ground level. If your plants are growing in containers, make sure you water at the soil line.

Avoid Wet Conditions

Since all of these diseases are spread by water, resist the urge to work with your tomato plants in any way if they are moist. This includes moisture from rain, dew, and irrigation.

On wet days, it’s best to skip checking your plants for pests or picking any pests from the leaves. Do not prune when plants are wet, and wait to stake or train plants that require additional support or adjustment until they are dry.

You should even avoid going out to harvest tomatoes in this type of weather. If an extended period of rain is in the forecast, consider picking the fruit in advance of inclement weather, or wait until plants have dried again.

Apply Mulch

This may not seem like an obvious step, but an application of mulch can also help to prevent contaminated soil from touching the leaves.

Another benefit is that it can reduce the amount of humidity around your tomato plants. Lower humidity means any spores present are less likely to germinate and cause an infection.

However, you should wait until the soil has warmed up to apply mulch. Add three to four inches of organic mulch around the base of plants about three to five weeks after planting.

Grass clippings, wood chips, or straw that is free from weed seeds are all good choices.

Remove Infected Plants

Be vigilant about removing infected plants. In the case of late blight, all plants, including those that are not showing symptoms, should be removed and destroyed.

If you had a blight infection at some point during the growing season, bag up all the tomato plants and remove them from your property.

Do not add any of the plant material to your compost pile, and be sure to remove all parts, including the roots and any fallen debris.

Growers with fields should disc them deep underground, so that they will decay.

Rotate Your Crops

It’s human nature to want to keep growing plants in the same place where they have done well in the past.

However, this practice can favor infection.

Even if you didn’t observe any infections the previous season, the pathogens could be lurking at low levels, waiting to strike at an opportune moment. Rotating your crops will prevent this from happening.

You should rotate your nightshade crops every year, just to be safe. If you had a problem with Septoria blight last season, make that every two to three years.

And if you absolutely cannot rotate your tomato plants since you are short on space in the in-ground beds, consider growing them in containers instead.

If you are reusing the containers, sterilize them with 10 percent bleach first, and always use fresh soil.

In the case of late blight, Jean Ristaino et al, in an article published by the American Phytopathological Society, recommend planting non-host crops in a two to three-year rotation.

Treatment

It is possible to control Septoria if you catch the infection early enough. Aggressively remove the infected leaves and purge them from your property.

Do not add the material to your compost pile, and dispose of it in the trash, away from your garden.

Simply removing infected plant matter will not control early or late blight. You will need to use fungicides to manage these infections.

Fortunately, you have several options.

You can use the same kind of fungicide to treat each of these diseases. Apply them every seven to 10 days throughout the season.

If your weather is conducive to the spread of these diseases (i.e. humid and/or rainy), you can also consider using preventative sprays before the onset of an infection.

While the products described here have all been shown to be effective, fungi can develop resistance to fungicides if they are used frequently.

Check your plants periodically to ensure that the treatment is still working. If it isn’t, you may need to change which type of fungicide you are using.

Fortunately, all of the fungicides recommended here are in different classes, so you should be safe switching between them.

Organic Fungicide

If you are looking for an organic fungicide to use, you are in luck!

Bonide Liquid Copper Fungicide

Copper will kill all of these organisms. You can buy Bonide Liquid Copper Fungicide from Arbico Organics.

Synthetic Fungicide

Many of the fungicides commonly used to treat tomato diseases will treat all of these blights.

One thing to remember with the fungicides listed here is that you should stop using them five days before you plan to harvest your tomatoes.

Your choices include:

1. Chlorothalonil – Bonide Fung-onil Concentrate, available from Amazon

2. Maneb

Biofungicide

One of the microbes commonly used in the biological control of plant diseases is effective against early blight.

It is a strain of the bacterium Bacillus subtilis, which is also known as CEASE Biological Fungicide, available at Arbico Organics.

Learn more about using B. subtilis in your garden with this guide.

Inspect Your Plants Frequently

As with any infection, your best odds of success for treating these tomato diseases is largely dependent on whether you are able to catch them early enough.

Make a point to inspect your tomato plants on a regular basis, so that you can identify an infection in its early stages. The official term for this is “scouting.”

While you might be able to stop Septoria blight from spreading if you catch it early enough, that is not the case for early or late blight.

But you can eradicate the plants from your garden to prevent further spread, and take steps to protect any tomatoes that you wish to grow next year.

Starting an aggressive campaign with fungicides as soon as you detect an infection – or even preventively, if the conditions are conducive to the spread of blight – may help to save your tomato crop.

Have you had to fend off one of these diseases? If so, let us know how you fared in the comments below.

And read on to learn about other disorders that can strike tomatoes:

© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Product photos via Arbico Organics and Burpee. Uncredited photos: Shutterstock. With additional writing and editing by Allison Sidhu and Clare Groom.

Tomato blight: treatments the gardening experts swear by

(Image credit: Getty Images/ NurPhoto)

Every year gardeners will desperately seek out a tomato blight treatment to help salvage their homegrown crop of tomatoes.  

Even if you're an expert at growing tomatoes, chances are you'll have encountered this devastating disease at some point.

Tomato blight – or Phytophthora infestans – otherwise known as late blight, is among the worst problems affecting tomatoes. It is the same fungus that can turn potatoes to mush and similarly affects tomatoes, which are cousins of the tubers. 

One moment your plants can be looking lush and healthy, the sweet smell of the ripening fruits filling the air – but then within only a few days the plants can be ravaged by blight which can sweep through them like wildfire. 

So arm yourself with the knowledge of how to avoid the disease, or know the best tomato blight treatments if it does affect your plants.

(Image credit: TI Media)

Tomato blight – treatments for outdoor and indoor crops

Because tomato blight is spread by airborne spores carried on the wind, and it likes warm, wet conditions, outdoor grown tomatoes are more susceptible to it that those grown in the greenhouse or polytunnel.  

Tomatoes are therefore a perfect choice for greenhouse ideas, or for growing in other environments under cover.

That's not to say that greenhouse crops are completely in the clear. Given the right conditions, late tomato blight can just as easily ravage an indoor tomato crop, but it is easier to control the environmental conditions under cover, such as keeping rain off the plants.

The same tomato blight treatments apply whether you grow your tomatoes indoors or outdoors.

(Image credit: Getty Images/ Daniela White)

What does tomato blight look like?

Tomato blight is a fungal infection that appears on different parts of the tomato plant. 

'In the early stages of late tomato blight, the bottom leaves get affected first with black rings of powdery blight. This makes the leaves turn pale green to a musty yellow in color and appearance,' explains Tammy Sons of Tennessee Wholesale Nursery .

'The leaves eventually get so infected they drop. As the blight progresses up the stalk of the tomato vine, the tomatoes get brown spots on them as the entire plant becomes infested. End-stage blight makes the entire tomatoes rot from the blight infection,' Tammy adds.

(Image credit: Annaick Guitteny)

The signs of tomato blight in the order they are likely to appear are:

Tomato blight can kill a plant within a week, so it's important to keep looking out for any telltale signs, and act quickly as soon as you spot them.

(Image credit: Getty Images)

How do you stop tomato blight?

The simple answer is that you can't stop tomato blight altogether – but you can take steps to prevent the chances of infection occurring.

'There are no chemical controls for tomato blight available to the home gardener,' says Simon Crawford, breeder at Burpee Europe . 

But rather than turning to tomato blight treatment once your crop has been affected, 'two other key methods should be used to control the disease: environmental management and the use of resistant varieties,' Simon continues.

(Image credit: Getty Images)

Environmental controls for tomato blight

The following environmental controls can help to prevent the occurrence or spread of tomato blight:

(Image credit: Getty Images)

How to stop the spread of tomato blight

If the worst happens and you do find signs of blight on some of your plants, then  the best tomato blight treatment is to remove these infected plants immediately to try to prevent the spread to other plants.

Check tomato plants regularly during the growing season, especially when the conditions are warm and wet.

'If you can, burn blighted plants and tomatoes,' explains gardening expert Monty Don in a video for Gardeners' World . 'Or compost the foliage and fruit, if you have a good composting system, as composting kills off the spores,' he continues.

It's important that you do no plant your tomatoes next to potatoes, which can also be victims of late blight, but carefully choose your tomato companion planting.

(Image credit: Burpee Europe)

Can you eat tomatoes with blight?

If you have an infected tomato plant, while you would not want to eat any tomatoes that are obviously affected by blight, any ripe tomatoes that don't show signs of blight are still perfectly good to eat.

However, 'if you leave tomatoes on a blighted plant, they won't ripen,' says Monty Don. He advises harvesting any green tomatoes that have no signs of blight and turning these into green tomato chutney.

(Image credit: Future / Annaick Guitteny)

Grow blight resistant tomato varieties

'Many modern tomato varieties have made growing outdoor tomatoes easier because of earlier ripening and improved disease resistance,' says Simon Crawford.

There are a number of varieties that have been bred with blight resistance. Simon Crawford lists the following varieties:

Tomato ‘Merrygold’. 'This is the world’s first blight resistant orange fruited variety. This plant is high yielding, producing a mass of brightly, rich orange tomatoes.' 

Tomato ‘Cocktail Crush’. 'With super blight resistance, this variety is ideal for growing outdoors.' 

Tomato ‘Crimson Blush’. 'This blight resistant beefsteak tomato is sweeter than other beefsteak varieties.'

Tammy Sons recommends some further blight resistant tomato varieties: 'Tommy Toes are heirloom red tiny tomatoes, robust in flavor and very juicy; Legend variety is a red beefsteak and a favorite of most commercial growers; Juliet is a small hybrid red tomato; and Manyel is a yellow tomato also low in acid.'

There are more varieties that you can try, so do your research before planting.

(Image credit: Burpee Europe)

Tomato blight treatment – baking soda

Some gardeners swear by a tomato blight treatment using baking soda.

The US Department of Agriculture advises creating the following solution to help prevent the disease or provide a tomato blight treatment.

To one gallon of water add:

Spray the tomato plants with this solution, and reapply it regularly to maintain its efficiency, USDA advises.

So while there is no way to completely stop the chance of your tomatoes ever developing tomato blight, there are many ways you can reduce the chance of infection, or prevent its spread to your entire crop. 

These are among the many vegetable garden ideas to consider when planning your plot.

Rachel is senior content editor, and writes and commissions gardening content for homesandgardens.com, Homes & Gardens magazine, and its sister titles Period Living Magazine and Country Homes & Interiors. She has written for lifestyle magazines for many years, with a particular focus on gardening, historic houses and arts and crafts, but started out her journalism career in BBC radio, where she enjoyed reporting on and writing programme scripts for all manner of stories. Rachel then moved into regional lifestyle magazines, where the topics she wrote about, and people she interviewed, were as varied and eclectic as they were on radio. Always harboring a passion for homes and gardens, she jumped at the opportunity to work on The English Home and The English Garden magazines for a number of years, before joining the Period Living team, then the wider Homes & Gardens team, specializing in gardens.

what is the cause and how to treat

06/21/2022 19:53 Anastasia Romanova

Blossom end rot appears on already formed, but immature fruits. Most often, it affects tomatoes in greenhouses. With this disease, a brownish spot appears on the top of the fetus, which gradually increases and in the final stage looks like a cavity with hardened dry dark tissue. The causes of the disease mainly lie in the mistakes in growing tomatoes. Plants need to be treated with drugs or folk remedies.

Causes of blossom end rot

Most often this is a non-infectious (physiological) disease, but there is also a bacterial variety that is caused by pathogens living in the soil. The main cause of the disease is calcium deficiency, and it is usually associated with unfavorable growing conditions and improper care.

What contributes to the development of blossom end rot:

How to treat blossom end rot

To begin with, all affected fruits must be immediately removed and disposed of. After that, you need to make a top dressing with a calcium content, taking into account the weather. In cold weather, it is better to spray tomatoes with soluble calcium preparations on the leaves. In warm weather, fertilize the soil, writes Novy Ochag.

Tomato blossom end rot preparations:

Requires two treatments with either of these drugs 10-14 days apart.

Folk remedies for the treatment of blossom end rot of tomatoes:

Dark spots on tomatoes can form not only on fruits, but also on leaves and stems. In addition to blossom end rot, there are several other tomato diseases that cause dark spots on tomatoes.

Blossom rot on tomatoes: treatment

Blossom rot or "bump" on tomatoes appears as dark spots on the tops of fruits

Blossom rot on tomatoes is a common problem that gardeners face quite often. This disease is remarkable in that it does not affect the tops of the plant, but only the fruits - brown spots appear on them, which rot, and, accordingly, lead to damage to the crop.

What to do and how to deal with blossom end rot on tomatoes? The answer is simple: in order not to face significant damage from the disease, treatment should be started at the first signs of it. And even better - think in advance about preventive measures and cut down the vertex rot in the bud.

Contents

What is blossom end rot, its symptoms on tomatoes as well as in greenhouses.

The classic symptom of the disease is the appearance of watery brown spots on the tops of tomato fruits. The spots quickly increase in size, blacken and become wrinkled (skinny). These areas will eventually rot, so diseased fruits should be picked up and discarded.

Blossom rot on tomatoes - close-up photo

Attention!

The tip of the tomato is the tip of the fruit, the “butt”, the place opposite the attachment of the stem.

Tomato blossom end rot is not a fungal and contagious disease (unlike the same Phytophthora ). It refers to physiological disorders caused by an imbalance of calcium in the plant body. In addition to tomatoes, this trouble can happen with peppers, eggplants, zucchini, cucumbers, melons, pumpkins.

Since blossom end rot is not fungal in origin, adjacent bushes are not affected. But saprophyte fungi intensively populate the damaged tissue, resulting in a black stain.

Symptoms may occur at any stage of fetal development. But most often they appear for the first time when the fetus is one-third to one-half of its full size. That is, green, not yet fully grown, tomatoes are more often affected. They begin to quickly turn red and fall off. The tissue in the affected area softens and rots.

Sometimes there are cases of damage to tomatoes from the inside. With this course of the disease, there are no visible signs. The fruits quickly turn red and fall off. Rot can only be detected when cutting the vegetable.

This is how blossom end rot looks on tomato fruits

Important!

Diseased fruits are not used for seed collection. They are also not recyclable. However, you can eat such tomatoes - if you first cut off the areas affected by vertex rot.

Causes of blossom end rot on tomatoes

The main reason for the development of the disease is lack of calcium in the plant . At the same time, its content in the soil is often sufficient, but for some reason the culture cannot absorb the required amount of this important trace element.

The following factors can interfere with the full absorption of calcium:

Prevention of blossom end rot on tomatoes

The most effective measures to combat blossom end rot of tomatoes are preventive measures. These include variety selection, seed and soil preparation, as well as specific growing practices and protective spraying.

Choice of variety

It has been noticed that tomatoes with elongated and creamy fruits, as well as large beef tomatoes, are most susceptible to blossom end rot. Therefore, when growing them, preventive measures should be taken especially seriously.

Varieties resistant to blossom end rot require less attention. Among them: Rotor F1, Grand Canyon, Khokhloma, Pink Elephant, Chukhloma, Benito F1, Bolshevik F1, Pharaoh F1, Toch F1. Also, small-fruited tomatoes, such as Cherry, rarely get sick.

Baby Cherries rarely get blossom end rot

Seed preparation

Care should be taken to disinfect seeds before planting. They are pre-placed in a 2.5-3% solution of potassium permanganate for half an hour. Then rinse well and dry.

Copper sulphate has similar properties. Tomato seed material is disinfected according to the following scheme:

Soil preparation

Before planting, the area where the vegetable crop is planned to be planted must be treated. In autumn or spring, one of the ingredients is added for digging:

They help reduce soil acidity and improve plant uptake of nutrients. When planting seedlings in each hole, it is useful to add wood ash (1/2 cup) and ground eggshells.

The addition of lime, chalk, dolomite flour to the soil contributes to soil deoxidation, which means it reduces the risk of tip rot

Preventive care rules

The following recommendations will also help prevent the development of tip rot:

Mulching the soil under tomatoes helps to retain moisture in the soil longer, which means it serves as a prevention of blossom end rot

When harvesting, the remains of diseased plants and fruits must be destroyed. When growing tomatoes, you should follow the crop rotation, alternating crops. If this is not possible in a greenhouse, green manure is sown in early spring before planting seedlings: mustard, oats, colza.

Treatment of blossom end rot on tomatoes with calcium preparations

But what to do and how to deal with the disease if you did not manage to prevent it and blossom end rot on tomatoes has already broken out? Of course, treat diseased plants. This is usually done by introducing additional top dressings with a high calcium content.

Generally, blossom end rot on tomatoes is treated with calcium nitrate (calcium nitrate). The solution is prepared according to this recipe: 10-15 g of calcium nitrate is diluted in 10 liters of water. With the same composition, you can also water the plant under the root, using 2 liters per bush. A sufficient content of boron in the soil will help to improve the absorption of calcium, therefore, before processing with saltpeter, it is advisable to add boric mineral fertilizer (boric acid).

Calcium nitrate can be used for both treatment and prevention of blossom end rot on tomatoes

What is tomato blossom end rot and how to treat it with calcium nitrate will be discussed in the video:

A good effect in the fight against the disease is given by a solution of calcium chloride, which is easy to purchase at a pharmacy. The drug is proven, cheap and available for use, diluted easily and quickly. For treatment, 1 ampoule of calcium chloride (10 ml) is dissolved in 6 liters of water and tomatoes are sprayed with this solution 2 times a week until the symptoms of the disease disappear.

In order to save tomatoes from the top rot of tomatoes as quickly as possible, you can use the Brexil Ca industrial tool. It contains calcium, boron and a complex of other nutrients that are well and quickly absorbed by the plant. To prepare a solution, 25 g of the product is diluted in 10 liters of water. Process the stem, leaves and fruits of the plant.

And if you use folk remedies?

Top rot on tomatoes is treated with available folk remedies.

Wood ash

Ash - an effective folk remedy for blossom end rot

To eliminate the damage, an infusion of wood ash is made, for which 100 g of ash is taken for 1 bucket of boiling water.

The agent is dissolved in boiling water and allowed to infuse for several hours. Then the resulting composition is filtered and poured into a spray dispenser, with which diseased bushes are treated.

Wood ash can also be applied dry. 3 handfuls of the product are scattered around the root and water the soil well.

Oak bark

Oak bark contains calcium, iron and many other useful trace elements that help prevent blossom end rot.

A decoction of oak bark also helps. 5 g of oak bark is poured with cold water and boiled for 15 minutes. Cool and filter. Additional water is added to make 10 liters of solution.

The vegetable crop is sprayed with the prepared composition.

Soda ash

Soda ash is highly alkalizing and helps with topping on tomatoes

Experienced gardeners often use soda ash. Prepare and use the composition according to this recipe: dissolve 2 tbsp in a bucket of water. l. funds, then carry out watering or spraying tomato bushes several times until the problem is completely eliminated.

Egg shells

Place the egg shells in a saucepan. Pour it with water and boil for several minutes. Cool to room temperature and infuse for about 12 hours. Then the solution is filtered and sprayed with tomato bushes.

Eggshell - a source of calcium, which is necessary for healthy tomato fruits

Increasing plant immunity - additional help in the fight against blossom end rot

As an effective adjuvant therapy, in addition to direct medical preparations, agents to enhance plant immunity are often used.

Learn more