If you are among the 90 percent of gardeners that grow tomatoes, understanding the diseases that affect the plants is something you should learn. Many gardeners find that growing tomatoes is frustrating because the plants are susceptible to infections.
By knowing the common plant pathogens, you learn how to apply preventive measures to curb infections before they wreak havoc on your plants.
Disguised plant diseases necessitate diligent preventative measures. Plant pathogens such as bacteria and fungi work behind the scenes on the microscopic level. By the time you notice a disease on your plant, it’s often too late.
Treating your plants with pesticides that may contaminate your fruits is the last thing you want to do. For organic gardeners, this is an added challenge because they must learn how to manage tomato plant diseases without chemicals.
While there is a right time and place for chemical treatment, the vast majority of scenarios can and should be addressed with an organic approach.
11 Common Tomato Plant Diseases
We’ll now discuss the most common tomato diseases. It is impossible to exhaust all the potential diseases your plants may encounter because many are specific to certain regions. As your primary focus, let’s explore the challenges you are most likely to face, plus teach you how to stop the disease right at the primary stage.
Damping Off
Damping off is a tomato plant disease which is a fungal ailment. Damping off arise either from seedling collapse or incapability to emerge from the seed. For many home gardeners, the effort put on starting tomato seeds is over the top, only to realize that the effort put is succumbed to waste because of damping off.
As noted, damping off is more common from poor air circulation, compacted soil, or poor drainage. Also, the fungal ailment can arise from poor air circulation for your seedlings.
Signs of Damping Off
Damping off is more likely to be noticed on smaller seedlings than larger crates. Most common indication to look out for is the falling over and dying around the germination stage as well as emerging from the soil. Stems can also darken at the lower section while beginning to the shurrivel.
Preventing and Treating Damping Off
While there is no treatment for plants affected by damping off, there are proactive measures that can be implemented to eliminate the problem completely. Damping off can be prevented by using sterilized potting soil and small fans to improve air circulation.
Bacterial Canker
Clavibacter michniganesis is the bacterial pathogen responsible for this infection. Infection occurs naturally, but can be easily introduced to your garden through tools and previously infected plants. Splashing water containing the bacteria onto the plant can deliver the infection. The bacterium waits for wounds to initiate infection.
Signs of Bacterial Canker
Bacterial canker is often misidentified as cloudy spot disease.
The telling features include the burst yellow patches and yellowing of the ripening red tomato fruits. These dots are surrounded by dark borders. The presence of dark edges around the spots is one of the distinguishing features that indicate the presence of bacterial canker, as opposed to cloudy spot disease.
Preventing and Treating Bacterial Canker
Bacterial canker is one of the bacterial plant diseases that has no known treatment options. They must be removed immediately. Additionally, one must refrain from planting tomatoes in the same soil for a minimum of three years.
Always ensure to either burn or incinerate the plants, as composting them is not an option.
Although treatment isn’t often effective, bacterial canker on fruit-bearing trees can be prevented.
- Rotate Crops
It is crucial to rotate crops to mitigate disease and bacterium build-up in the soil. Avoid planting tomatoes and any nightshade relatives in the same garden bed the following year.
- Clear Out Garden Weeds
Bacterial canker is rampant in the Solanaceae family, which includes many garden weeds. Thus, maintaining a garden devoid of weeds is a simple measure of minimizing the spread of bacterial canker.
Anthracnose
Anthracnose disease is caused by the fungus Colletotrichum phomoides. This fungus thrives in hot, humid climates, and the spores spread very easily with the use of overhead irrigation, sprinklers, or heavy rainfall. Splashing water onto infected soil and onto the stem or leaves of the plant is another way to infect the plant with anthracnose.
Signs of Anthracnose
Signs of anthracnose are observed as the tomatoes begin to ripen. They develop a dark bull’s eye on the fruit which is located on the blossom end of the tomato. The dark spots are sunken and soft which makes them very visible.
In some instances, the fruit’s flesh may completely and utterly rot off. The inside of a tomato with the infected black spot is bland, and the skin appears to be unappealing to look at. Harvesting fruit at its peak ripeness often helps prevent further spread.
Preventing and Treating Anthracnose
- Water Correctly
Make sure you do not water plants incorrectly. This might require you to change your approach toward watering. Do not water the leaves, but rather let the water drip on the roots.
- Try Liquid Copper Sprays and Sulfur Powders
Beginning in the early spring of each year, once the leaves start to bud, you can use liquid copper and sulfur sprays weekly. The best time to apply these sprays is in the early morning.
- Use Neem Oil Spray
You can use Neem oil for much more than just removing mold on plants and fungi, because it is organic, it is perfectly safe to use. It can often help in stopping the fungi before it affects the plants when applied early.
Early Blight
Most of you are probably familiar with blight. There are two types, early and late. The early blight is caused by the fungus known as Alternaria solani.
This is why it is best to change the location of your tomato plants, as early blight persists in soil year-round. If a gardener does not properly rotate crops, they will lose the plants to early blight due to the fungus in the soil. Once blight infests soil, it can persist for long stretches of time.
Signs of Early Blight
Tomato plants infected with Early Blight will show black or brown patches on the leaves. This disease initially attacks the oldest leaves, then gradually progresses upwards. Each spot is bound to develop a ring as the disease progresses which is akin to a target. Gradually, the infested leaves will dry and fall off.
Additionally, the fruit stems can also be infected and black, sunken lesions can develop. Early blight can result in a plant with scant few leaves. If extremes of high humidity and high temperature coincides, most of the plant will shed foliage.
Preventing and Treating Early Blight
Surprisingly to most, the solution to removing early blight is not as simple as it may seem. But with the following suggestions, you may find it easier to remove early blight.
- Use Proper Plant Care Recommendations
The application of proper preventive practices such as blight control methods is critical in preventing late blight. Make sure to rotate crops, remove debris, weeds, and give sufficient space between tomato plants for air circulation. Also, ensure to water tomato plants at the base, not at the stem.
- An Organic Fungicide
Business that sells fungicides which are compatible with organic gardening are becoming more popular. One of such is Safer, which is available at local garden centers. Fungicides for gardens are also able to treat plants with early blight.
- Use Liquid Copper Fungicide
Alternatively, you can spray the plant using liquid copper fungicide concentrate. This is also organic and must be applied on a dry day. On the next dry day, prune the lower branches and then apply the treatment again in one to two weeks.
Late Blight
Light blight, one of the most prevalent tomato plant diseases, is caused by a fungus called Phytophthora infestans. This fungus is active during the last growing season’s cool, rainy weather and is known to cause late blight.
This diseases of plants is very serious as it destroys the entire plant. Mother nature inflicts diseases on plants; the complete defoliation of the tomato plant occurs within two weeks of the initial symptoms appearing. This highlights the importance of closely monitoring plant progress to prevent the ailment from escalating.
Signs of Late Blight
Check for the symptoms of late blight after the first stage of cold weather or during the rains. The leaves of the plant may be damaged by a frost, showing irregular green-black continua, and in the case of the tomato, the leaves can show large brown spots. These fruits may also show large, irregular, brown spots that eventually rot.
As for the leaves, their spots will exhibit rapid growth; in addition, white mold may grow on the edges of the affected spots. Depending on the disease severity, the fruit may also have dark lesions that are shiny. Finally, all the affected leaves and stems will wilt and change color to brown, and this process occurs two weeks after the first symptoms appear.
Preventing and Treating Late Blight
As Late Blight is one of the hardest diseases to treat, prevention becomes the first step. Try purchasing and planting disease-free plants and seeds. You will also have to ensure that the garden beds are clear of all debris to ensure disease harboring materials are eliminated.
- Water Properly
As a plant owner, ensure that your plants are watered adequately. Make sure that the base of the plant receives the moisture and water the leaves. Also, avoid overhead watering because that spreads diseases.
- Pull Out Plants
Plants infected with late blight are often required to be pulled out from the garden, and it is advisable to destroy them. They should not be composted but rather trashed or burned to prevent the spread of the spores.
- Use Copper Fungicide
In some situations, late blight can be controlled using a copper fungicide.
Septoria Leaf Spot
A fungus called septoria lycopersici causes this infection to overtake the foliage of the plant. It is one of the diseases that can be caused by a fungus and can take over your plants.
Just like several other fungal diseases, it can be caused by overwatering the plants. The watering can spread the spores to the leaves of the plants, and that is how the disease starts.
The fungus also thrives during warm, moist weather, and high humidity. This fungus is most active when the temperature is between 68°F and 77°F.
Signs of Septoria Leaf Spot
As the plants grow, their lower leaves develop yellow spots with dark gray centers and dark borders as the fungus continues to grow.
Eventually, the dark spots that are formed turn black, thus completing the infection. Those black spots are the bodies that generate spores and propagate the disease. The leaves begin to die and shed off the yellowing plant. The yellowing process takes time as the fungus spreads throughout the plant.
Defoliation lowers the strength of the tomato plants, lowers the quality of the tomatoes, and leaves the plant exposed to other diseases.
Preventing and Treating Septoria Leaf Spot
Removing Septoria Leaf Spot is challenging, but focusing on prevention measures such as proper watering and spacing the plants for proper air circulation is beneficial. If your plants do end up getting infected, here are some strategies.
- Rotate Crops
Always practice crop rotation to reduce the inoculum. Debris removal during crop rotation minimizes the disease’s potential to survive in the soil for years.
- Use a Garden Fungicide
You may use organic garden fungicides as treatments. Foliar and plant-wide spray applications should be done to eliminate the spores. Best results come from copper fungicides and those containing chlorothalonil.
Fusarium Wilt
Plants experiencing health issues and then sudden wilting may be experiencing fusarium wilt. Theucumber plant disease Fusarium oxysporum f.sp. Lycopersici will attack the tomato plant’s vascular system the same way the veins in your body are attacked.
Fusarium oxysporum f.sp. Lycopersici damages xylem vessels, which are crucial for the transport of water and nutrients from the roots to the leaves. Tomato plants will often wither and die.
Signs of Fusarium Wilt
Signs of fusarium wilt in crops develop rapidly. The plant remains active but starts wilting without any water deficit. Some may claim that the plant may begin to show these signs from one side but eventually enclose the entire plant. The plant will be dead within a few days.
Preventing and Treating Fusarium Wilt
Prevention is the most effective strategy for managing Fusarium wilt as no treatment has proven effective. Most gardeners attest that their plants “die” within a week.
Focus on proven methods to prevent fusarium wilt. Here are some suggestions.
- Crop Rotation
Rotating crops is a vital trick to preventing this fungus from taking over your garden. Avoid planting tomatoes in the same place in the garden for the following year.
- Purchase Resistant Varieties
Purchase wilt resistant varieties in case of these reoccurring problems. The fungus survives in the garden soil from the previous year, so ensure that plants are available that can survive it.
- Try Actionvate
Actinovate, a pesticide and fungicide designed to combat certain Fusarium Wilt-causing diseases, is a possible treatment option. It helps to soil through the introduction of beneficial microbes that can struggle with the roots and foliage.
Verticillium Wilt
This is yet another fungal ailment that affects the tomato plant. Verticilliurn albo-atrum is the fungus responsible for this infection. It infects the roots and moves upwards through the xylem vessels with the water. Once inside the xylem vessel, it hampers the flow of water and nutrients to the leaves.
Signs of Verticillium Wilt
This fungal infection results in yellow patches developing on the lower leaves. The leaves’ brownish veins progress to die and fall off with the plant leaves.
Essentially, the disease is responsible for water and nutrients distribution and leads to the plant’s demise. The plant does not thrive for some time, and it appears that the plant’s growth is stunted, but eventually, the plant perishes.
Preventing and Treating Verticillium Wilt
Just like with vertebrate wilt, fusarium wilt cannot be cured. Once the plant is contaminated, it cannot be saved, thus, the best alternative is to eradicate the plant and discard it in a trash bag.
- Keep Your Plants Healthy
Ensuring proper watering, scheduled dead branch pruning, and fertilization with a low-nitrogen, high-phosphorus formula, may aid in combating the disease.
- Soil Solarization
Soil verticillium wilt infests the soil, but can be exterminated through soil solarization. This approach destroys all fungus within the upper six inches of the soil.
Mosaic Virus
Tomatoes and several other vegetable crops are susceptible to the Mosaic Virus. While it does not usually kill the majority of the plants, it certainly diminishes quantity and quality, diminishing all your efforts.
Mosaic Virus symptoms are characterized by the open wounds the virus creates on the leaves of the plant, which makes it easier for the virus to gain entry. Therefore, for the sake of your plants, it is best to avoid contact, even as a smoker, as tobacco is a reservoir for the mosaic virus.
Signs of Mosaic Virus
The petal patterns of mosaic light green and yellow on leaves, and the mottling of fruits are characteristic of the virus. Also, some leaves which are deformed and look like ferns, rather than the expected tomato plant leaves have also been described.
Preventing and Treating Mosaic Virus
Mosaic virus is a terminal viral disease. While it does not technically require treatment, mosaic virus is one which all gardeners have to strive to combat by all means. Use fungicides for treatment and avoid keeping seed from crops that are infected.
Here’s how to prevent the mosaic virus.
- Treat with Neem Oil
Certain pests have the capability to transmit the mosaic virus. Therefore, regularly applying pest control treatments, including neem oil, can help prevent these pests from infesting your plants.
- Use Row Covers
Row covers can act as an alternative method to protect your tomato plants from insect infestations and help shield these vulnerable crops from pests.
- Always Clean Garden Tools
Garden tools are known to be a common transmission pathway for this virus. It’s critical to disinfect tools used in the garden, including ties, pots and other equipment, with a solution containing one part bleach to four parts water.
Leaf Mold
Another form of fungal disease affecting tomato plants is Leaf Mold. The fungi Fulvia fulva, which thrives in stagnant air with high humidity, is generally seen in tomatoes grown in greenhouses.
Signs of Leaf Mold
The low air movement near the soil layer makes tomato plants with older, bottom leaves vulnerable to fungal infections. Several pale green to yellow spots form on the leaves which, over time, coalesce and turn yellow.
These spots can also become filled with fungus spores, taking on a grey hue with a velvety texture when humidity is high. In advanced cases, the lesions merge together, resulting in the complete destruction of the foliage.
Leaf mold develops not only on the leaves, but also on the stems, flowers, and fruit of the plant. Both immature and ripe fruits develop dark, leathery lesions at the stem end.
Preventing and Treating Leaf Mold
As with most fungal diseases, prevention of leaf mold centers around improving airflow. Proper watering practices are also essential. To prevent water from soaking the leaves, always stake your tomato plants.
- Use an Appropriate Fungicide
Preventative fungicides containing either chlorothalonil or copper fungicide are some of the most common treatments in leaf mold.
Bacterial Spot
Bacterial spot is caused by the bacterium Xanthomonas vesicatoria. Instead of red tomatoes, this bacteria attacks green tomatoes and also affects pepper plants. Bacterial spot is most common in wet seasons with excess rain and humidity.
The bacteria survives the winter on infected plant debris and other plants. To prevent them from thriving, make sure to remove plant debris at the end of the growing season. The bacteria thrive in wet and warm conditions.
Most outbreaks of bacterial spot occur after heavy rainstorms when bacteria take advantage of newly exposed leaf surfaces.
Signs of Bacterial Spot
Evidently, as the bacterium progresses, it inflicts a range of harm on the plant, including the lesions on the leaves and fruits, decreased productivity, and shedding of leaves. We can observe small, irregular and scalily darkened lesions on the leaves and lesions on the fruits too.
Additionally, the lesions on the leaves can be surrounded by a yellow ring as a result of die back. Eventually, the leaves fully rip and begin the process of detaching from the plant. Shedding of leaves is a regular occurrence with these bacteria.
Preventing and Treating Bacterial Spot
Once bacterial spot is established it is extremely difficult to control and prevent the occurrence of these diseases within your garden. The bacteria travel through water, splashing from one plant to another.
The first step is to avoid overhead watering. Drip irrigation is a necessity, especially for tomato plants.
- Prune Your Plants
It’s essential to prune your plants to encourage good air circulation.
- Spray a Copper Fungicide
The most effective organic treatment for bacterial spot is to treat the plants with copper fungicide. This method is effective against these bacterial diseases.
Work to Prevent Tomato Plant Diseases
Sadly, the recurring theme is that eliminating tomato plant diseases is difficult, if not impossible, in the majority of circumstances.
This is why the focus is to eliminate the occurrence of such diseases by proper watering and gardening practices. Such measures will ensure the plants remain as vigorous as possible.