Tomatoes can be finicky. Even though it is relatively easy to grow a nice big leafy plant, sometimes there are tomato disorders which rear their ugly little heads. So when it is time to for the actual fruit to appear, things could go a little haywire. This article discusses some of the most common tomato disorders and how to resolve them.
No Fruit or Low Yield
This is likely the very first issue of the common tomato disorders you might see on your tomatoes during the season. As I mentioned above, while it is relatively easy to get a green and lush, leafy plant, it can be much harder to get fruit to set.
Symptoms and Causes
There are a a number of conditions which could prevent your blossoms from setting fruit:
- Temperatures above 90 or below 50 degrees – pollination fails
- Dry soil – blossoms will dry and fall off before they can be pollinated if the soil is too dry.
- Not enough sun – tomatoes need at least 6 hours of sun a day, better with 8 hours per day.
- Too much nitrogen or not enough phosphorus fertilizer
Treatments
If you are wondering why your tomatoes aren’t setting fruit, or are experiencing low or no yield on your tomatoes, head on over to my article all about this.
The very first thing to try when waiting for fruit to set is to shake your plant. This will help the pollen drop from each flower. For even better results, shake your plants every morning to increase your yield. I discuss all about why this works in the article about pollination mentioned above.
Also you should add some ‘super bloom’ or ‘super phosphate’ fertilizer. The phosphate number on the package should be high. Try 0 – 20 – 20 for best results. Phosphate increases blooming. If you’re interested in why phosphate is so critical, read my articles on fertilizers and this one on tomato nutrition (for the planting hole)
If you are experiencing a heat wave, there might not be anything you can do; just wait it out. And if you live in super hot areas, check out my post on pollination for some alternate strategies to grow tomatoes in hot climates.
Blossom End Rot
Symptoms and Causes of Blossom End Rot
Blossom end rot can be the most heartbreaking of tomato disorders. Symptoms are soft brown or black spots on the bottom end of the tomato, away from the stem. Sometimes the soft spot will harden a bit into a dark scar. These dark brown areas can get bigger as the tomato grows. If wet weather or overwatering continues, the area is also susceptible mold.
Blossom end rot is caused by a calcium deficiency when the plants are young and the fruit is just starting to develop. Wet weather and overwatering will absolutely exacerbate the problem. Sometimes, even cool temperatures early on in the growing season can make an existing condition worsen.
Magnesium fertilization can also increase the chances of tomato disorders, especially early in the season.
Prevention and Treatment
First and foremost, to prevent blossom end rot, always add eggshells to your tomato planting hole at the beginning of the season. This will increase the calcium level in your soil and knock out the majority of issues.
Next, maintain a uniform supply of moisture through irrigation and adequate soil mulches. Try not to overwater, and of course don’t let the soil completely dry out. Remember that the important part is two inches below the surface. The sun dries out the top layer more quickly, but there is often moist soil down below. Mulches or water halos will keep the soil cooler and more evenly moist.
Avoid excessive potassium or magnesium fertilization as these nutrients will compete with calcium for uptake by the plants. Epsom salts is an example of a magnesium source, so do not apply to garden soil unless a recent soil report indicates an extreme magnesium deficiency.
A soil analysis report will help you determine any imbalance. The soil pH should be about 6.5, with adequate calcium levels. If calcium levels are not sufficient but the soil pH is correct, then a calcium supplement (like the eggshells) should be added into the soil before planting. However, if you already have blossom end rot on you fruit, you could side dress the plant with some ground eggshells. There is also a commercial foliar calcium spray which could help, but is generally not as effective as improving the soil.
Avoid ammonia- based fertilizers , as this also will compete with calcium. Many commercial fertilizers contain ammonia. Also to note – ammonia stays in the soil and is one of the causes of soil acidification. It also contributes to runoff into our streams and lakes, polluting our groundwater for drinking and potentially harming fish. So, please try to stay away from ammonia based fertilizers.
Leaf Roll
Tomato foliage can exhibit what is known as leaf roll. This is a relatively common tomato disorder where the plant exhibits the upward curling of leaves most commonly during high temperatures and drought. It may also occur if there is an unusual cold spell shortly after planting. Basically, it is a sign that your plants are stressed.
Symptoms and Causes of Leaf Roll
Leaf roll of tomatoes may be caused by high temperatures, prolonged periods of wet soil conditions, and drought. It may also occur when tomatoes are pruned severely, or if the plant is in a pot which is too small for its roots. You will notice the leaf roll by an inconsistent upward curling of the leaflets, which could progress to affect most of the foliage.
Leaf roll is sometimes accompanied by the darkening in color of the leaf to a purplish or blackish color. You may see this on newly transplanted seedlings which are exposed to more light or more cold (or more heat) than they were used to in the greenhouse or nursery. If left un-addressed, or if the conditions are very severe, the leaf could burn. The condition of leaf roll also occurs sometimes when the plants are under the stress of a heavy fruit set.
Prevention & Treatment
The symptom of leaf roll usually does not significantly damage the crop. Transplant tomatoes outside only after the threat of severe weather has passed, and protect them from overly bright conditions if they are not used to it. Bring starts outside for several hours every day prior to planting to slowly acclimate them to your local bright sun. They most likely weren’t so exposed at the start of their lives in a greenhouse, and need some time to adjust. Use wind protectors for a week or so after transplant as a defense against the harsher afternoon rays or other variable temps.
Tomatoes should be kept consistently moist but not overly wet. Plant in well-drained soil and irrigate them during periods of drought. Better yet, use a drip system which keeps consistent moisture. If you have particularly problematic weather, a moisture gauge can help.
Growth Cracks
Growth cracks are round lines – circles or spirals – which form on the top or stem end of a mature tomato. Usually the cracking occurs during the ripening process, as the tomato reddens.
Symptoms and Cause of Cracking
Tomatoes crack when variable environmental conditions — such as dry or drought followed by heavy rain or watering — encourage rapid growth during the ripening process. Some cracks may be deep, allowing mold or decay to enter the tomato and cause fruit rot.
The most important thing to note is that the crack itself does not make the tomato inedible. The crack is a cosmetic blemish which can be cut from the tomato the same way you would cut the stem off prior to using. The issue is when the crack stays moist, as from heavy rain, with no sun to dry the area out. Then, the tomato becomes soft and can start to decay.
In California gardens, while we may get cracking, the rot is easily preventable due to our lack of summertime rain. This decay usually happens only to our late season crops in the fall when the rains come.
Prevention
But of course, we all want perfect tomatoes, right? Here’s how to avoid cracks altogether. First, make sure your plants have the correct nutrition for the stages of growth. If you hand water your tomato plants, never water from above – always water at the soil level. You almost never want to get the fruit wet. Maintain even soil moisture with consistent watering, but do not overwater. Drip irrigation and / or a water gauge will help you maintain and monitor for overly wet soil.
Some tomato cultivars are prone to cracking, including many of our beloved heirlooms (Cherokee Purple comes to mind). Others are crack-tolerant. Hybrid tomatoes and paste varieties tend not to crack.
Catfacing
Symptoms and Causes of Catfacing
Catfacing is a tomato disorder which scars the blossom end of the tomato but there is not real rot. There are a few ways to tell the difference between cracking and catfacing. While cracking occurs on the top of the tomato, catfacing occurs on the bottom, or the blossom end. I’ll get to why this is in a moment. Another difference between the two is that catfacing will show up on a young green tomato. Cracking will not show up until the tomato starts ripening.
Catfacing appears as dark spots and crevices on the blossom end of your tomato. This is largely an aesthetic problem, with the caveat that in extreme cases the available ‘meat’ will be far less. However once you trim off the skin scars, the tomato is edible with no loss of flavor. Since it may be difficult to get good burger slices from a catfaced tomato, they are fine for salads and using in tomato sauce. Just make sure to trim all of the brown skin, as it is tough and leather-like.
Catfacing is not common, and it is not fully understood. However it is related to abnormal blossom formation. This is why it happens at the blossom end of the tomato. When two petals of a pollinated tomato flower grow together, even after the baby tomato forms, this is what is thought to cause the cat-faced scarring. In the first picture above (of the green tomato), you can almost see the flower petals in the triangle forms of the scars.
In the photo above you can see an abnormal flower formation. It has way too many petals and many are connected.
Some sources blame the abnormality on cold nighttime temperatures during fruit set. It might also be due to extreme variations between daytime and nighttime temps. Beefsteak, Cherokee, and other varieties of large fruit size are the most susceptible. I have never seen catfacing on a hybrid or on paste tomatoes.
Sunscald
Symptoms and Causes of Sun Scald
Sunscald – as you can guess by the name – occurs when tomatoes are exposed to the direct rays of the sun during hot weather. I’m generally talking about weather above 95 degrees for more than 8 hours a day. The problems are more pronounced with tomatoes which are not acclimated to such heat, such as newly exposed tomatoes due to excessive leaf pruning.
Often with heat waves, this will last for several days in a row, exacerbating the problem. The fruit is quite literally cooking on the vine. You will notice discoloration, much like what happens to sun scalded squash. The area will become soft and perhaps even shriveled. Decay-causing fungi frequently invade the damaged tissue, and fermentation of the affected area could follow.
Prevention
Shade exposed fruits when heat waves threaten. Try to install a removeable shade cloth several feet away from the plants. Make sure there is an open area for heat to escape. If you put shade cloth close to or on top of the plants, be sure to use a breathable fabric, as heat could build up under non-breathable covers. Also shade the soil, as a healthy plant which has sufficient moisture will better tolerate the heat. Even when watering daily, heat waves could suck out the moisture in a raised bed in a few hours.
Never prune more than about 20 percent of the leaves, and only from the bottom and center of the plant. Pruning is meant to encourage root growth, improve air circulation, and prevent disease. Disease infrequently attacks the top of the plant, rather ‘jumps’ from the soil to the lower leaves. Unless you have a removeable shade cloth you should never prune from the top or outside if you can help it.
Also, control stress and leaf diseases, because leaf loss or leaf roll could expose the tomato fruit to too much sun too quickly.
Let me know if these tips help out this year with any tomato disorders you have with your tomatoes. And let me know if there are any other issues with your tomatoes you’d like me to cover! Just tell me in the comments area below. Happy planting!!
