The Garden

10 Tomato Diseases & Issues

If you are anything like me then you have a deep love of growing tomatoes. If I could only grow one thing it would definitely be tomatoes. They are the basis for so many recipes, making them a staple in just about every kitchen. But if you have ever grown tomatoes then you probably know there are more than a few challenges you can face in the quest for delicious juicy tomatoes!

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On my micro homestead, I only use heirloom seeds, and my tomatoes are no exception. I love the varieties that you can find in heirlooms plus there is the rainbow of colours that are available. I have tomatoes that range from black to green to yellow and a few that a multicoloured. Oh, and did I mention that it means I can save my seeds and save money? If you haven’t noticed I am pretty passionate about heirloom seeds!

But in order to ensure a bountiful harvest so that you can make some delicious homemade tomato sauce, salsa or whatever you have planned. You will first have to avoid any serious tomato diseases and issues. So let’s take a look at 10 common tomato diseases and issues.

1. Early blight

Early blight is a pretty common fungal disease that occurs in tomatoes (and potatoes). It is caused by a soil bacteria that goes by the name of Alternaria solani and it can present itself in all parts of the tomato plant (stem, leaves and fruit). While it is not necessarily a death sentence for your plant it will weaken your plant and diminish your harvest. 

Early blight typically affects mature plants, but it can occasionally occur on seedlings as well. It tends to take hold in damp conditions, primarily on stressed plants or those that have poor soil. It can be hard to deal with but it is not nearly as deadly as late blight! But more on that horror in a bit.

As I mentioned, early blight is caused by the fungus Alternaria solani which is in the soil. It can be introduced to your garden either in new soil, or it can be on plants you purchase or even in the seeds you plant. Unfortunately, it can persist in your soil for at least a year. This is a good reason to practice plant rotation as it is never a good idea to keep planting the same plants in the same spots.

So what does early blight in tomatoes look like? As I mentioned it affects all aspects of the plant, so let’s look at them one at a time.

The Leaves

You will likely notice spots on the leaves with concentric circles. These will eventually start to turn yellow and the leaves will die off.

The Stem

On the stems of your tomato plant, you may start to notice some dark areas. They can start off small but then grow and get a bit sunken in. As they grow they will get bigger and longer and then you will start to see the same concentric circle markings that are present on the leaves.

The Fruit

The fruit is the last place you will see evidence of early blight. If however, it gets this far then you will see spots start to show up on the fruit. These will develop and take on the same sunken profile like those on the stem, eventually showing the distinct concentric circle pattern.

So how can you prevent early blight from infecting your previous tomatoes? You can do a few things which I have listed below:

  1. Look for varieties that are resistant to early blight (none will be immune).
  2. Make sure to prune the bottom 10-12” on your plant to allow for good air circulation.
  3. Get trusted seeds, getting cheap seeds from some shady guy is a good way to end up with blight (among other things).
  4. Reduce stress on your plants
  5. Practice crop rotation

2. Late blight

This is one tomato disease you want to avoid at all costs. If your tomatoes are stricken with it then I am truly sorry. Late blight can affect tomatoes and also potatoes (it was responsible for the Irish potato famine!). So this is nothing to mess about with! It strikes fast and with a vengeance, so you will want to be on the lookout for any symptoms that it has found its way into your yard.

As opposed to early blight, late blight is not caused by a fungus, but instead by an oomycete. Specifically, it is caused by Phytophthora infestans (even the name is yucky) and it tends to strike when the weather is cool and wet.  Much like early blight, it attacks all parts of the tomato plant.

So how do you know if this beast has gotten its death grip on your tomatoes? Let’s look at how it manifests in the different parts of the plant.

The Leaves

Late blight can show up on your tomato leaves as irregularly shaped brown splotches that have a greasy appearance. If the weather gets warm and wet the splotches can even develop a disgusting looking ring of white mold.

The Stem

You will see blacked areas appear on the stems of the affected tomato plants.

The Fruit

On the fruit you will see the same greasy looking, irregular dark spots. 

So you have it, what can you do now? In all honestly, not much. This disease can overwinter in the soil and as I mentioned can also infect any potatoes you may be growing. Copper sprays may help but you may just want to remove the affected plants, just don’t go putting them into your compost!

Blossom end rot

3. Blossom end rot

It can be soul-crushing to see beautiful ripe tomatoes and then to turn them over and see a disgusting brown spot. Before we get into how to prevent blossom end rot let’s first understand what it is not. 

  • Blossom end rot is not a disease, it is an issue that can be encountered under certain conditions. 
  • Blossom end rot is not typically due to a lack of calcium in the soil.

That is not to say that calcium is not a key component of this tomato issue as it is. But typically it is not a lack of calcium in the soil which leads to blossom end rot. So there is not much point in running out and throwing eggshells at your poor point. Eggshells in the garden is a whole other topic for another day.

What does cause blossom end rot is overwatering which leads to issues as it impedes the plant’s ability to absorb calcium from the soil and move it properly to the developing fruit. It can also be caused by either extreme heat or cold, acidic soil or overenthusiastic nitrogen fertilization. In rare cases, it can be caused by a lack of soil calcium. So if you are dealing with blossom end rot and you are not overwatering then you can always pick up a soil testing kit to see what may be going on.

There are also certain types of tomatoes that are more susceptible to suffering from blossom end rot. Typically plum tomatoes will be more prone to it. In any case, if you see any fruit that has been affected then remove it and add it to your compost. Once it has been affected with blossom end rot it will not develop and ripen normally.

The best ways to avoid blossom end rot are regular deep watering, adding garden lime to the soil (to increase water and nutrient uptake) and the use of a low-nitrogen and high phosphorus fertilizer.

Cracked tomato

4. Cracking

Cracking on your tomatoes is one of those things that is more of a presentation issue than anything else. That said they should be harvested as soon as you see cracking has occurred and brought inside to ripen. This is especially important for green tomatoes as they would not have enough time to ripen before they rot because of the cracking. While these tomatoes are fine to eat they are definitely not insta worthy. Given that we all want to grow beautiful tomatoes, let’s look at how this travesty can be avoided. 

Cracking tends to occur when tomato plants get a lot of water after being in a drought scenario. This can be caused by heavy rains after it has been very dry, or by overwatering after realizing that you forget to water them in a while (not that you would do this). Cracking is even more likely to occur in fruit that is just about to ripen. 

So it is better to water your tomatoes every few days, and when you water them make sure to water them deeply. Watering your tomato plants deeply also helps to drive the roots down deeper into the soil which helps to build stronger plants.


5. Catfacing

Catfacing is a purely visual issue, just one more way your tomatoes will not be insta worthy. It is caused by fasciated blossoms, which is a common issue with heirloom tomatoes. A fasciated blossom occurs when two or more blossoms become combined into a single fruit. So you end up with usually very large mutant looking tomatoes. They are fine to eat but if you would rather not then keep an eye out for any fasciated blossoms and remove them before they can set fruit.

6. Verticillium Wilt

Yet another soil-borne fungal tomato disease! This one can live in the soil for many years and can also affect other vegetables. The name is somewhat misleading as it doesn’t always present with wilting in the plant.  Typically the leaves of your tomato plant will turn yellow, dry up and they may or may not wilt in the process. The yellowing usually is seen first towards the bottom of the plant affecting the older leaves first. The blotches then darken and dry up and the disease will move up the plant.

Verticillium wilt will stunt your plant’s growth and will also reduce your tomato yield. It tends to occur more often in cooler temperatures but can occur at any point in the growing season. You are best served to remove any affected plants and make sure that you do not include them on your compost

The best way to prevent verticillium wilt is to select resistant varieties and practice crop rotation.  

7. Bacterial speck

There are a few bacterial problems that plague tomatoes and bacterial speck is one of the common ones. The culprit of this disease is the bacterium Pseudomonas syringae. It strikes when the weather turns cool and wet and there is no cure for it and while it won’t kill your plant it will have a negative effect on the amount of fruit produced.

You will know you have it if you see tiny, dark spots that have a yellow border, present on both the fruit and the leaves. These spots can take many forms and may be raised, sunken or flat.

The easiest way to avoid bacterial speck is to keep water off the leaves as much as possible. Pruning the bottom 10-12” of the plant will help to increase airflow and also reduce splash-back onto the plant. If you see any evidence of this disease you will want to make sure to remove any affected plants and do NOT put them in your compost. It is also a good idea to clean your garden tools as this disease is easily spread between plants. It can also be transmitted on your hands, gloves or through the water.

Tomato blossom drop

8. Blossom drop

Blossom drop on your tomato plant is very common and extremely frustrating. You get all excited to see your healthy tomato plants producing flowers only to see them dry up and fall off before setting any fruit! There can be multiple causes of this common issue but the primary one is temperatures that are either too high or too low, But there are other causes such as:

  • Lack of pollination
  • Too much nitrogen
  • Too little nitrogen
  • Heavy fruit sets
  • Too much humidity
  • Not enough water
  • Too little humidity
  • Stress

So now that it seems like I listed just about everything let’s focus on the things that are within your control. Start by growing varieties that are best suited to your hardiness/climate zone. Help to increase the chances of pollination by gently shaking your plants when they have flowers. Tomato plants are self-pollinating but that doesn’t mean you can’t give them a helping hand. Don’t go crazy with or forget to fertilize them.

I have mentioned this a few times already but you can keep a lot of tomato issues/diseases at bay by watering regularly and deeply. Finally, keep in mind that sometimes the plant knows best. If there is already a lot of fruit on the plant then it may drop blossoms as it can only support a certain number of fruit.

Tobacco hornworm

9. Caterpillar damage

If you have ever grown tomatoes there is a good chance you have had a run-in with a hornworm. Even if you didn’t see them (but they are HUGE so you probably have) you would have definitely seen the damage they can do.   A fully grown hornworm can pretty much destroy an entire tomato plant in a single day. There are actually two types, Manduca quinquemaculata (tomato hornworm) and Manduca sexta (tobacco hornworm). They are both just as bad as each other and don’t be fooled by their names, they both love tomatoes. 

If you are seeing plant damage, tomatoes that are eaten or clumps of black poop then I would strongly suggest you arm yourself with a black light and head out into the garden at night.  Why? Well, fun fact, hornworms (of both varieties) glow under black light! You can then pick them off and toss them into a jug of soapy water or feed them to your chickens if you are lucky enough to have them!

10. Anthracnose

Anthracnose is another fungal tomato issue, this one will cause your fruit to rot. It is caused by a fungus from the genus Colletotrichum, which are responsible for many plant issues. This is another disease that can wreak havoc on your plants in a relatively short period of time. It rears its ugly head when conditions are cool and moist. Without moisture, the fungus will not be able to germinate or infect plants.

You will know that you have anthracnose if you see dark lesions on your plants. The blemishes can appear on the fruit, stem or leaves and tend to be water-soaked with the renters often developing gelatinous pink clumps of spores when the weather is warm and moist.

Affected plants must be dealt with quickly as anthracnose can overwinter in the soil, on seeds and in any garden debris.

As with any disease, the best medicine is prevention, so here are some ways you can avoid having to deal with or spread anthracnose.

  • Don’t save seeds if you have had any anthracnose in your garden
  • Try to choose resistant tomato varieties
  • Clean and sterilize all garden tools if you have an outbreak
  • Do NOT compost any infected plants
  • Prune the base 10-12” of your plant to allow for good airflow

So there you have it, 10 common tomato diseases and issues that you are likely to encounter if you decide to grow tomatoes. Many can be mitigated in the same ways which is a good thing! Have you dealt with any of them before?

Happy Gardening!

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