Tomato Diseases – Causes, Prevention & Treatment

Even the most experienced gardeners can sometimes face some challenges related to tomato diseases when growing tomatoes.

Sometimes, tomatoes get diseased, and if not treated, these could die. That is why is important to recognize these diseases in time and act quickly to solve the problem.

tomato diseases

In this article, I will talk about tomato diseases, their causes, and how you can prevent or eventually treat them.

Many tomato diseases are caused by fungal pathogens and some of them are caused by bacterial or viral pathogens. But some diseases are caused by water mold pathogens, phytoplasma, or diseases that are actual physiological disorders and not really diseases.

Fungal Diseases

– Alternaria Stem Canker

Alternaria Stem Canker is caused by the Alternaria alternata f. sp. Lycopersici that is attacking the leaves, fruits, and stems.

A specific symptom of this disease is the dark brown sunken lesions on the part of the stem which is close to the soil.

Other symptoms are the concentric rings on the fruits. These rings can appear while the fruit is still on the plant, however, these can appear even after the fruit is harvested.

This fungal disease will also appear on the leaves as dark brown lesions because the fungus produces a toxin that kills the tissue between the veins.


Alternaria Stem Canker is spread by airborne spores.

The soil can be also infected and so this can spread the disease when the soil comes in contact with your tomato plants.

When you water your plants from above, you can help the spores to be spread. Also, dew and heavy rains can lead to the spread of it.

Prevention & Treatment:

As prevention, I can advise you to plant varieties that are resistant to Alternaria Stem Canker diseases. Varieties like ‘Phoenix’ and ‘Mariana’ can be a good choice.

However, when I say resistant, I don’t mean immune. So, these can still get diseased, if the circumstances are not preferred.

Make sure you always water your tomato plants from the base of the plant. Never sprinkle their leaves, as this can be damaging.

A drip irrigation system or a soaker hose can be used, if you don’t want to water each plant one by one with your watering can. These systems can also help you to keep your tomato plants healthy by consistent watering.

A morning watering routine can also help to prevent the disease. The excess water has enough time to evaporate until the evening.

If the disease appeared in your garden despite all your efforts, then you can still save your tomatoes if you act as soon as you observe the first symptoms.

As a treatment, you should apply fungicide spray that contains chlorothalonil, which fights against the Alternaria alternata f. sp. Lycopersici.

You can apply fungicide on your tomatoes 4-6 weeks prior to harvesting the tomato fruits.

– Anthracnose

Anthracnose can infect a large variety of plants, not only tomatoes. This disease can attack leaves, fruits, and flowers as well.

Usually, when it comes to tomatoes, this disease attacks the fruits that are ripe or overripe.

Anthracnose is caused by the Colletotrichum coccodes fungus that develops on the lower leaves that are already damaged from pests or other diseases like the early blight.

The most common and typical symptoms are small and slightly sunken round lesions, that start as half-inch black spots. Then these lesions become bigger and bigger.

On the surface of the lesions, you can see salmon-colored spores, especially when the weather is moist.

Another symptom is when the roots are affected, but you can observe this only when the fruits start to ripen. This is also known as black dot root rot.

Black rotting spots will appear on the roots and can completely rot the cortex of the roots.


Anthracnose is mostly caused by a wet environment.

Prevention & Treatment:

Use disease-free seeds, as the fungus can be also in the seeds.

You can plant varieties that are resistant to Anthracnose. ‘Chef’s Choice Orange Hybrid’ can be good for this reason.

You should avoid watering your tomato plants from the top, especially when the fruits are ripening.

Using soil that is good quality and well-draining, also helps to prevent Anthracnose.

Remove the lower leaves that are touching the ground.

Rotating the crops is also a good idea because spores can overwinter in the soil. This will stop the spread of the diseases.

For example, one year you plant your tomatoes in one corner of your garden, and the next year, you can plant them in another corner of the garden.  Instead of tomatoes, plant other crops that are not in the Solanaceae family, so potatoes, eggplants, or peppers are not a choice.

As a treatment, you can use the same fungicides that are effective against Alternaria stem canker. The fungicide should contain chlorothalonil.

Copper sprays also help to fight this disease.

– Black Mold

Black Mold is caused by the Alternaria alternata fungus. This disease attacks the ripened fruits, especially when the weather is humid and warm.

Once infected, Black Mold can appear on the fruit even after harvesting.

The lesions caused by Black Mold can look very similar to those caused by Blossom End Rot. However, these will not appear on the blossom end of the fruits, but the stem end.

The size of the lesions can be from small spots to large, circular, and sunken lesions. These can go deep into the fruit and cause the fruits’ rot.


Wet, humid, and warm weather is the main cause for the development of Black Mold.

Prevention & Treatment:

Black Mold can be a bad surprise in anyone’s garden in the late season and can spread very quickly. Once it entered the garden, it is difficult to stop it.

Therefore, prevention is the best treatment.

First of all, don’t let your tomato fruit overripe. As soon as they are ripe, harvest them straight away.

The longer a ripe fruit stays on the vine, the greater the chance to get infected by Black Mold.

You can also spray the plants with fungicide if you are aware that the weather will turn in the Black Mold’s favor.

If the disease appears on your crops, then you can spray the plants with fungicide as soon as you see the first signs of mold.

– Botrytis Gray Mold

Botrytis Gray Mold is caused by the fungus named Botrytis cinerea. It is a very aggressive fungus that can infect over 200 types of plants and can be easily spread by the wind.

This disease can appear on the stems, leaves, and flowers of tomato plants. The greenhouse tomatoes will not be an exception of getting it.

The most common and typical symptom is the gray mold that covers the infected areas.

Usually, the tomato fruits will be diseased while they are small and green. White, circular spots will appear on the fruits. As these are ripening, the spots will turn yellow.


The main cause of this disease is too much rain, wet, humid and warm environment, but it can be triggered also by watering the plants from the top.

Prevention & Treatment:

As I mentioned above several times, never water your tomatoes from the top. Using a dripping system or just simply pouring the water directly on its soil, will save you so much trouble.

Watering the right way will prevent many diseases, not only fungal diseases.

Clean tools are also essential. Always clean your tools after and before working with them, so these will not spread any spores and will reduce the chance of developing Botrytis Gray Mold.

Using fungicide as a treatment can be a good idea, however, this can be a bit tricky. The fungus Botrytis cinerea can develop resistance very easily to the fungicides, so better to ask for advice from professionals in your area to find out which fungicide works in that area.

– Early Blight

Early Blight is a very common tomato disease and it is caused by the Alternaria solani fungi.

It appears as small brown or black spots on the stems, mostly on the older leaves, and even fruits.

The spots, as they enlarge, form a classic concentric rings pattern, and the area around the spots turn yellow.

The spores of this disease can be spread through water or wind.


Early Blight can appear in your garden mostly when the environment is too wet for too long.

Prevention & Treatment:

You can prevent Early Blight by using resistant or tolerant tomato varieties and by rotating your crops in your garden.

Unfortunately, Early Blight fungi can remain in the soil through the winter, so if you have a possibility to test the soil before planting the tomatoes, that would be a lifesaver.

Always water the tomatoes from the bottom, do not let them touch each other, and prune them regularly to ensure a proper airflow between the leaves.

If the tomato plant gets infected, remove the diseased leaves and dispose of them. Never put diseased plants into the compost.

Mancozeb, copper, or chlorothalonil fungicides are good to use as a treatment for Early Blight.

– Fusarium Wilt

Fusarium Wilt is another devastating tomato disease and it is caused by the Fusarium oxysporum f. sp. Lycopersici type of fungus.

The spores of this fungus can live in the soil for many years and it will cause the wilt of the tomato plants that are planted in the infected soil.

The first symptoms of Fusarium Wilt are that the plant starts losing its green color and the lower leaves start to wilt. Sometimes wilting occurs only on one side of the plant.


The fungus found in the soil passes upward into the stem through the roots. This will block the water-conducting vessels causing the plant to become yellow and wilt.

The stem will be looking healthy from the outside; however, if we cut the stem lengthwise, on the lower part of it, we can observe dark brown discoloration of the water-conducting vessels.

The fungus can infect the plant through the wounds on the roots. However, this can be spread through seeds or transplants.

Prevention & Treatment:

The best prevention is to grow varieties that are resistant to at least one of the Fusarium Wilt races, such as ‘Beefmaster’, ‘Better Boy’ or ‘Floralina Hybrid’.

Raising the soil’s pH to 6.5 – 7.0 and using nitrate nitrogen is also a good idea in terms of prevention as this reduces the chance of disease development.

Unfortunately, once the plant gets diseased by Fusarium Wilt, there is no chance to save the plant. There is no chemical treatment available to treat Fusarium Wilt.

– Leaf Mold

Leaf Mold disease is caused by the Passalora fulva fungus. This can be spread through rain, wind, or tools.

The main symptoms are pale green leaves or yellowish spots on the older leaves and then spreading to the younger ones.

The yellow spots can grow and the whole leaf can become a distinctive yellow.

When the humidity is rising, the yellow spots can be covered with gray, velvety spores that are produced by the fungus.

If the disease becomes severe, this can kill the foliage and attack the stems, flowers, and fruits as well. The fruits will start to rot on the stem end.


Leaf Mold is mostly caused by high humidity, wet environment combined with high temperatures.

However, the fungus can survive on crop residue and soil; therefore, can be easily spread by the soil and dirty tools.

Prevention & Treatment:

Infected foliage should be removed from the garden to stop the spreading.

To prevent the development of the disease, use clean tools, keep the garden tidy and airy and never sprinkle the foliage with water. Always water from the bottom.

Crop rotation also helps in prevention.

As a treatment, fungicides that contain copper, chlorothalonil, or mancozeb are perfect to fight Leaf Mold.

– Buckeye Rot

Buckeye Rot disease is caused by the fungus Phytophthora nicotianae var. Parasitica. And it affects only the tomato fruits.

The main and first symptoms are brownish spots that appear on the fruits, usually on the point where this touches the soil.

While the spots are growing, dark and concentric rings appear. Buckeye Rot lesions look similar to the Late Blight lesions.

But Buckeye Rot lesions remain firm and smooth, while the Late Blight lesions are rough and sunken.

When moist and warm conditions are given, the lesions of Buckeye Rot get covered by white, cottony fungal spores.

If not treated, Buckeye Rot makes the fruits rot.


Buckeye Rot appears on the tomato fruits when the condition is wet and warm for a longer period of time, and it is combined with poorly draining soil.

The bad news is that the fungus can be spread with the surface water and rain, and it can survive in the soil.

Prevention & Treatment:

To prevent Buckeye Rot, make sure your garden is tidy, there are no weeds, the tomato plants are pruned and planted with the needed space between the plants.

Staking, mulching, rotation, and sanitation can also prevent Buckeye Rot disease.

As a treatment, fungicides that contain copper, mancozeb, or chlorothalonil are perfect to stop the disease.

– Seedling Disease (Damping-off)

Seedling Disease is another fungal disease and it is caused by the fungi Pythium and Rhizoctonia.

This disease will fail the seedling to emerge from the soil, but even if this makes its way out, this will wilt and die quickly after emerging.

Some seedlings may survive, but these will have water-soaked areas on their lower part of the stem, close to the soil.


Seedling Disease appears when the seeds are sown too early because these fungi will thrive in cold, wet, and rich soil.

Prevention & Treatment:

If you want to grow tomatoes from seeds, make sure you sow them indoors in clean and sterilized containers and potting mix.

Seeds and seedlings don’t need fertilizer. A nitrogen-rich soil can also be a trigger for Damping Off. Fertilize the seedling only after their first true leaves are out.

To prevent damping off you must pay attention to your watering technique and frequency. Do not leave the soil to dry out completely, and do not overwater it.

Water your tomato seedling when the top of the soil is dry.

– Fusarium Crown and Root Rot

Fusarium Crown and Root Rot are caused by the fungus Fusarium oxysporum f. sp. Radici-lycoperici and its spores can live in the soil for many years.

This disease usually affects the roots; therefore, the first symptoms are impossible to be seen in time.

The roots develop dry brown lesions and as the disease spreads, it goes up on the stem and attacks the foliage. The lower leaves will lose their green color, becoming yellow on the margins and then they die.

Lesions can appear on the stems as well.


Fusarium Crown and Root Rot is a severe disease that can cause the younger tomato plants to wilt and stunt growth. This disease can also kill a mature plant.

Poorly draining soil and cool weather (between 50-70° F/ 10-21°C) is the best environment for the disease to develop.

Prevention & Treatment:

As prevention, you can steam the soil to sterilize it, but obviously, this is a choice only if you grow the tomatoes in a greenhouse or growing bags.

If you grow them in the ground, you should choose varieties that are resistant to this disease.

Unfortunately, there is no cure for this disease.

If your tomato plants are affected by it, dispose of all the diseased plants, including the roots.

– Powdery Mildew

Powdery Mildew is caused by the Oidiopsis Taurica fungi and affects only the foliage of the tomato plants, not the stems or fruits.

Affected leaves will be covered with powder-like patches on the upper and lower sides.

Spots of dead tissue that are surrounded by yellowish halo can be also seen on the older leaves.


Powdery Mildew usually appears on the plants in the late season, when the humidity is high and the temperatures are between 60-77° F/ 15-25° C.

The spores of the disease can be carried by the wind as well.

Prevention & Treatment:

To prevent the disease, water your plants from the bottom and keep them tidy. Staking will also help in ensuring a proper airflow between the tomato plants.

As a treatment, you can use neem oil, Bacillus pumilus (biofungicide), or fungicide sprays when severe infections occur.

If the infection is only at the beginning, you can just remove the affected foliage and dispose of it.

– Septoria Leaf Spot (Leaf Canker)

Septoria Leaf Spot is caused by the fungus Septoria lycopersici and can affect tomato plants while these are affected by Early Blight as well.

This disease’s first symptoms are small, circular spots that enlarge over time. These spots can often look like water-soaked spots.

In the middle of these spots, dark and pimple-like structures will appear and these will produce the spores of the fungus.

The spores can be spread by the wind, rain, tools, insects, and even clothing.


Septoria Leaf Spot can appear on your tomato plants when the environment is humid and warm.

Your plants can get the disease from infected debris as well, or from insects that carry the fungus.

Prevention & Treatment:

To prevent the spread of the disease, always use clean tools, keep your garden weed-free and clean the garden properly at the end of the season.

Make sure to dispose of all the infected debris.

Use fungicide sprays as a treatment.

– Southern Blight

Southern Blight is caused by the fungus Sclerotium rolfsii (also called Athelia rolfsii) and this produces resting structures, called sclerotia; therefore, this disease can survive in the soil for a very long time.

The first symptoms are lesions on the stems, close to the soil, and these spread higher up the stem over time.

Because of the lesions, the tomato plant starts to wilt, and then white mats of fungal threads will develop on the affected areas.


Septoria Leaf Spot appears mostly when the temperatures are very high (above 85° F/ 29° C) combined with high humidity.

Prevention & Treatment:

The best prevention is crop rotation with non-susceptible crops.

Always remove the affected plants from the garden.

Using calcium-nitrate when transplanting can prevent the disease as well.

Unfortunately, there is no treatment for this disease, and the spores can survive in the soil for many years.

– Verticillium Wilt

The Verticillium Wilt disease is caused by Verticillium dahlia and Verticillium albo-atrum fungi.

These fungi also produce resting structures (microsclerotia); therefore, it is impossible to get rid of them. This can affect a wide range of plants and can survive in the soil forever.

The first symptoms are V-shaped, yellowing leaves, that later turn brown and then die. If too many leaves are dying off, then the fruits can get sunscald; therefore, the yields are reduced.

The tomato plants will not always wilt.


Water clogged soil helps the disease to develop.

Prevention & Treatment:

Rotating crops and sanitizing the work tools regularly prevents the development of Verticillium Wilt.

Also, paying attention to the watering technique is essential. If the weather is hot and dry, then water your plants more often. But when it is rainy, you might need to skip watering for that day.

Choosing the right tomato variety that is resistant to the race of Verticillium Wilt predominant in your area will also save you from some problems.

– White Mold (Timber Rot)

White Mold is caused by the fungi Sclerotinia sclerotiorum and despite it is not a very common disease, can be very severe once it occurs.

This disease can kill your tomato plants very quickly and the spores can survive in the soil for up to 10 years.

The first symptoms may appear on the lower part of the stems, close to the soil, or the lower branches.

First, you will see water-soaked lesions and then bleached areas. These areas get covered with a white fuzzy mold, that can appear inside and outside of the plant.

As the disease spreads, this can attack the flowers, leafstalks, leaves, and stems. The fruits can be affected as well, and these will turn gray and then will rot.


Cold and wet climate is the main cause of the White Mold, but as I said, this can survive in the soil for a long time.

So, even if the environment is perfect for your tomatoes, they can still get infected by the disease.

Prevention & Treatment:

Preventing the disease is the best way to fight it. Crop rotation is one of the best ways of preventing it.

Also, sanitize your working tool regularly and prevent excess moisture around the tomato plants and in the soil.

If the soil is infected, you can sterilize it and you can add biofungicides to it that can kill the spores.

If your tomato plants are infected with Withe Mold, you can also use fungicides to treat them.

Water Molds

tomato disease - late blight

– Late Blight

Late Blight is caused by the water mold Phytophthora infestans and can cause severe infections and can kill your tomato plants in just like 10 hours if the conditions are favoring.

The first symptoms appear on the leaves. These will have lesions that look like water-soaked areas and these can rapidly spread and form oily purple blemishes.

The disease then will spread all over the tomato plant, including the fruits. These will become brown but will remain firm.

The disease will spread from one infected plant to the whole garden if you don’t act quickly.

Not only your garden will be affected, but your neighbors’ as well, because the spores can be carried by the wind as well.


The infection can appear on the plants when the humidity is high (over 90%) and the temperatures are between 60-78° F/ 15-25° C.

Prevention & Treatment:

Unfortunately, there is no treatment for Late Blight, however, you can slow it down with fungicides.

When you see the first signs of Late Blight on one of your plants, it is advised to destroy the plants, and treat the healthy ones with fungicides.

This way you can prevent the spread of the disease to other plants.

So, prevention is a must when it comes to this disease.

Keep your garden tidy, weed-free, and sanitize your tools frequently.

Avoid sprinkling water on the leaves of the tomato plants and make sure the airflow between the plants and their leaves is good enough.

– Phytophthora Root Rot

This disease is caused by the water molds Phytophthora parasitica and P. capsici and can affect tomato plants at any stage.

Symptoms cannot be seen in time, because this disease appears and kills first all of the roots or at least most of them.

When the disease is advanced, the tomato plants are wilting and drying, but at this time, it is too late to be saved.


The pathogen thrives when the soil is too wet and is not draining well.

Prevention & Treatment:

Crop rotation and keeping the soil consistently moist can prevent Phytophthora Root Rot.

Use well-draining soil and don’t overwater your tomato plants.

In some cases, fungicides can help to treat the disease.

Bacterial Diseases

– Bacterial Wilt

Also called Southern Bacterial Blight and it is a serious disease. It is caused by Ralstonia solanacearum also known as Pseudomonas solanacearum.

These bacteria will first attack the roots of the tomato plant through any kind of wounds found on the roots.

The bacteria then spread quickly in the water-conducting tissue and this will fill up with slime.

This slime stops the water to travel up into the plant; therefore, this wilts quickly, while the leaves stay green.


This disease is thriving in high humidity and temperatures and can survive in the soil for a long period of time.

Prevention & Treatment:

Crop rotation is a good idea in terms of prevention, but you should do it for at least 3 years.

Planting certified disease-free varieties, like ‘Kewalo’ can also prevent infestation.

As prevention, also use clean tools and keep your garden tidy and weed-clean.

Unfortunately, this disease cannot be chemically treated.

– Tomato Pith Necrosis

Tomato Pith Necrosis is mostly an early-season disease and it can appear in greenhouses or high tunnel tomato production as well.

This disease is caused by the bacteria that are soil-borne: Pseudomonas bacteria, Pseudomonas corrugate bacteria, and Pectobacterium carotovorum.

The first symptoms are black (necrotic) patches on the stem and these will spread along the stem and onto the leaf petioles.

As the necrotic areas grow, the bacteria enter into the stem and cause the stem to split, shrink and crack. This leads to a segmented or laddered stem.

This damage in the stem stops the water to climb to the rest of the plant, which causes yellowing and wilting of the plant.

Other symptoms can be the production of roots that grow out of larger stems. However, this can be a symptom of bacterial canker as well.

Also, the green fruits can become greasy and water-soaked, which is, again, a similar symptom to that of late blight.

To tell exactly which disease is affecting your tomato, you can take a sample to a lab, and they can tell you.


These bacteria infect the tomato plants when the weather is cloudy, cool, and wet.

Its severity depends on nitrogen fertilization during the early season of growth. Seedlings or young tomato plants don’t need nitrogen fertilizer.

Prevention & Treatment:

To prevent the disease, avoid overhead irrigation. A 3-year crop rotation is also good prevention because the bacteria live in the soil.

Keep your garden clean, and plant your tomatoes at the right time. Planting them too early in the spring can enhance the infestation.

Unfortunately, there is no chemical treatment for Tomato Pith Necrosis.

– Bacterial Canker

Bacterial Canker can lead to total crop loss and can infect tomato plants at all stages of growth. It is caused by Calvibacter michagensis subsp. michiganesis.

 The most common source of the bacteria is infected seeds, which will lead to infected seedlings and transplants.

The disease can infect the whole system of tomato plants. That means the bacteria will spread throughout the plant and will cause wilting, curled and yellow leaves, and later on, the death of the plant.

Bacterial Canker has a secondary infection type as well, which is when bacteria infect only the surface of the stems, leaves, and fruits.

This type of infection will cause spotting of the infected areas, which are also called “bird’s eye spots”. These lesions are raised and have a white halo.


It is easily spread with tools and can infect all your tomato plants quickly.

Wet weather is the perfect environment for this disease to thrive.

Prevention & Treatment:

Bacterial Canker is extremely difficult to control and cannot be treated.

Therefore, it is very important to prevent this disease.

You can prevent it by planting resistant varieties and using sanitized tools every time.

If your tomato plants get infected, it is very important to destroy and remove the affected plants.

In some cases, copper bactericides can prevent the disease, but this is not always effective.

Crop rotation is also a good way to prevent the infection and spreading of Bacterial Canker.

– Bacterial Speck

Bacterial Speck is caused by the Pseudomonas syringae pv. tomato bacteria and this can survive in the soil, infected debris and the surface of the seeds as well.

The typical symptoms are dark brown lesions on the leaves, stems, and fruits, and around these lesions, the tissue becomes yellow.


Bacterial Speck appears in cold weather and fortunately, the spread stops when the temperatures are high (above 75° F/ 24° C).

Prevention & Treatment:

You can prevent the development of Bacterial Speck by planting the tomato seedlings when the temperatures are rising.

Watering from the bottom and crop rotation are also good ways to prevent the disease.

Fortunately, Bacterial Speck can be treated with copper sprays or other fungicides.

– Bacterial Spot

Bacterial Spot disease is caused by Xanthomonas campestris pv. Vesicatoria bacteria.

Like many other diseases, Bacterial Spot can also survive from one season to the next one on infected debris, volunteer tomatoes, and weeds.

The symptoms of Bacterial Spot are very similar to those of Bacterial Speck; therefore, this disease is often misdiagnosed.

The main difference between the two is that Bacterial Spot disease will attack mature tomato plants as well, not only the seedlings.


Usually, this disease is spread by infected seeds.

Unfortunately, once the disease appears in a garden, it is very difficult to control or get rid of.

Prevention & Treatment:

Make sure you are buying disease-free seeds or seedlings. Also, adequate watering is a must when it comes to prevention.

As a treatment, you can use copper sprays. This will slow down the spreading of the disease.

Phytoplasma Diseases

Phytoplasmas are smaller than bacteria and act like viruses. Phytoplasmas are parasitic microbes and they need a live host for living.

– Tomato Big Bud

Tomato Big Bud is caused by the Candidatus Phytoplasma aurantifolia microbe.

The distinctive symptoms of the disease are large, swollen, and green buds that will not produce fruit.

The infected plants are often bushy, the leaves have disorders and their color is yellowish-green.


Tomato Big Bud disease is transmitted to the tomato plant by the beet leafhopper (Circulifer tenellus).

Prevention & Treatment:

Prevention is the best in this case, as this disease can cause huge problems in your crops.

Using fast-acting insecticides, like pyrethrins or azadirachtin, can prevent the leafhoppers to infect your plants.

Or if you want to go organic, you can use predator insects (ladybugs, green lacewings, assassin bugs) that will kill the eggs, nymphs, and adult leafhoppers.

Viral Diseases

– Tomato Spotted Wilt Virus (TSWV)

Tomato spotted wilt virus is a unique virus among plant viruses because this is the one that can infect most plants, including vegetables and ornamental plants as well.

This virus will turn the color of tomato leaves into a bronze one, and these will develop dead spots as well.

The virus can affect ripe fruits. These can turn blotchy with yellowish spots. These yellow spots may appear in concentric rings. Luckily, the fruits can be still eaten.


Tomato spotted wilt virus is spread to the Western flower thrips (Frankliniella accidentalis), onion thrips (Thrips tabaci), and chili thrips (Scirtothrips dorsalis).

Prevention & Treatment:

Planting resistant varieties, such as ‘Red Defender’, ‘Summerpick’, or ‘Quincy’ will save you from the stress of this virus.

However, the best way is to get rid of thrips, because this can save you from not only the tomato spotted wilt virus, but many other problems as well.

Unfortunately, there is no treatment for this disease, so if your plants get infected, you should remove all affected plants from your garden as soon as you see the first symptoms.

– Tomato Yellow Leaf Curl (TYLCV)

Tomato Yellow Leaf Curl virus is very damaging to fruits yields. The biggest problem is that tomatoes will not show any symptoms for 2-3 weeks after the infection happened.

The symptoms are upward curling leaves, that have yellow margins and are smaller than normal.

The growth of the plant is stunted and the flowers are dropping.

If the virus appears on your tomato plant while these are in their early stage of growth, then this will be unable to produce fruits.


TYLCV is spread by whiteflies. These can bring the virus into your garden from weeds such as different nightshades and jimsonweed.

Prevention & Treatment:

Keep your garden and its surrounding area weed-free to reduce the chances of whiteflies.

If you see whiteflies on your tomatoes, get rid of them with repellents: use a 0.25% or 0.5% oil spray (2-4 teaspoons of horticultural or canola oil mixed with a few drops of dish soap/ gallon of water) every week.

If the virus infects your tomato plants, you should get rid of the infected plants to stop the spread.

– Alfalfa Mosaic Virus

Alfalfa Mosaic Virus is fatal for tomato plants, but luckily, most of the time affects tomatoes that grow near alfalfa plants.

Symptoms are yellow leaves with some mottling on them and fruits with circular rings of dead tissue.

The virus attacks the vascular system of the tomato plant; therefore, the water and the nutrients cannot travel up in the plant and this leads to the death of the plant.


Most of the commercial alfalfa fields are infected with this Alfalfa Mosaic Virus.

The spread of the virus is caused by the thrips that travel from these fields to your garden.

Prevention & Treatment:

There is no chemical treatment for this virus, but you can try to prevent it.

My opinion is that you should not grow tomato plants at all near alfalfa.

However, if you still decide to do it, you can try to repel aphids from your garden.

To keep away aphids, you can use pesticides regularly, but this can harm other beneficial insects as well. So, pay attention to what kind of pesticides you are using.

Or you can use silver reflective polyethylene mulches to keep away these pests.

– Tobacco Mosaic Virus (TMV)

Tobacco Mosaic Virus symptoms are mild mosaic pattern on the leaves, stunted growth, and the leaves will be malformed and the plant will slowly die.

In time, dead tissue may appear on the fruits as well.

The Tobacco Mosaic Virus can survive in infected plant debris for many years.


TMV is spread mechanically. It can be spread with tobacco products as well.

Prevention & Treatment:

This disease has no treatment, but can be easily prevented.

The best prevention is to plant resistant varieties, such as ‘Estiva’, ‘Arbason’, ‘Geronimo’, ‘Bush Early Girl’, ‘Bush Celebrity’, Big Beef’, or there are many others available.

Prevention is when you also sanitize your tools, and work with clean hands, especially if you are a smoker.

Physiological Disorders

– Blossom End Rot

Blossom-end rot usually appears on the first flush of fruits and on the fruits that are not mature yet.

This physiological disorder appears on the blossom end of the fruit as a brown or black spot that will grow in time and make the fruit rot.

This disorder is caused by the lack of calcium in the fruit.

tomato disease - blossom end rot


The main cause for the lack of calcium in the tomatoes is the damaged roots.

These can be damaged because of the transplant, too much or too little watering, or other reasons.

Prevention & Treatment:

Make sure you don’t disturb the roots of your tomato plants.

Also, as prevention, you should fertilize your plants regularly and water them adequately.

Once the fruit is affected by blossom-end rot, that fruit should be discarded, because it cannot be saved, but make sure you add some calcium to the soil, so the rest of the fruits will grow healthy.

– Sunscald

Sunscald is another physiological disorder that appears on tomato fruits.

Usually, it appears on green fruits, and the lesions can lead to fungal diseases.


Sunscald is caused by the direct sunlight on the tomato fruits.

Prevention & Treatment:

Keep the foliage healthy to ensure shade for the fruits.

If there are exposed fruits, you can use a shading sheet for keeping the tomatoes out of the direct sunlight.

– Catfacing

Catfacing is the disorder when the fruit is malformed, usually on the blossom end.


Too hot or too cold weather during fruit set can cause this disorder.

Too much nitrogen in the soil or herbicides can also cause catfacing.

Prevention & Treatment:

Try using resistant or tolerant varieties, such as ‘Duke’ or ‘Walter’.

Adequate fertilizing and watering are a must when it comes to the prevention catfacing disorder.

– Fruit Cracking

Fruit Cracking is when the fruit outgrows its own skin and this cracks or splits.

tomato disease - fruit cracking


Fruits Cracking usually appears after heavy rains or when you overwater your tomato plants. The fruits absorb too much water and it grows quicker than their skin.

Prevention & Treatment:

Consistent watering is key in preventing tomatoes to split.

Also, you can opt for resistant varieties: ‘Marglobe’, ‘Jet Star VF’ or ‘Daybreak’ for example.

– Leaf Roll

Leaf roll is another physiological disorder that is caused by the tomato plants’ environment.

Symptoms are older leaflets’ upright curling, stiffness, and leathery feeling when you touch them.

Later on, the whole foliage can be affected.


Leaf Roll can appear on tomato foliage because of the high temperatures or too much or too little water in the soil.

This condition can appear especially when the tomato plant is stressed by the heavy fruit set.

Prevention & Treatment:

Consistent watering can prevent the disorder.

Wrap Up

Consistent watering and doing it from the bottom of the plant is key in preventing many diseases.

Using clean tools and working with clean hands is also a must.

To prevent the diseases, you can also use resistant or tolerant varieties.

I hope I did not miss out on any of the common diseases, but if I did, please let me know in the comments below.


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