Non-infectious Tomato Problems

Brian Jervis: Ask a Master Gardener

Thursday, June 4, 2020

Most of us have had our tomatoes in the ground for a while and are looking forward to some delicious fruit soon. However, our journey from planting to eating typically comes with a few challenges.

Tomatoes can be persnickety. Everything has to be just right to get fruit and then when things are going great, along comes an insect or a disease to frustrate your efforts.

We will talk about some of those issues in future articles, but first, let us talk about noninfectious diseases in tomatoes because most of these are the result of some sort of environmental challenge.

Blossom drop: Here is the scenario. Our plants are in the ground, we are getting flowers, and we are looking forward to those flowers developing into fruit. But instead, those flowers fall off and drop to the ground … thus the name “blossom drop.” Typically, we see blossom drop when we have settled into regular daytime temps above 90 degrees, as this heat inhibits pollination.

However, cooler temperatures can also contribute to blossom drop when our night temperatures are below 55 degrees. We have had weather like that recently, and some of you have been experiencing blossom drop due to cooler temperatures. However, once it warms up, you should begin to get fruit on your tomatoes.

Blossom-end rot: Blossom-end rot is pretty easy to spot when you notice the blossom-end of your tomato turning brown. Gradually, the brown spot gets bigger, is sunken and feels somewhat leathery. This area of the fruit then becomes susceptible to pathogens that result in the fruit rotting.

Blossom-end rot can be the result of several different factors; high temperatures, wind, fluctuating water availability and drought can all promote blossom-end rot. But so can excessive soil moisture for prolonged periods of time. These conditions inhibit the plant’s ability to draw up calcium from the soil, and so blossom-end rot is ultimately the result of a calcium deficiency.

However, adding calcium to the soil is not a solution to the problem because no matter how much calcium you add to the soil, the environmental conditions have not changed, and the plant is still not able to lift those nutrients up into the plant.

There are a lot of solutions online to blossom-end rot suggesting putting eggshells in a blender and sprinkling them around your plants. This will eventually add calcium to your soil, but it will not help solve the blossom-end rot problem, only time and drier conditions will do that.

Catface: Catfacing is an interesting one in that it shows up as misshapen fruit with what appear to be scars. Again, this is another temperature-related problem that can occur when temperatures are below 58 degrees when the flower is being formed. Turf-weed pesticides that contain 2,4-D can also be a contributor if they come in contact with your plant.

These are some of the main noninfectious disease problems we see in tomatoes, but you can learn about more on our website (tulsamastergardeners.org) by looking in our Lawn & Garden Help section under vegetables.

Garden tips

• Yellow leaves on plants may be due to too much water in the soil. With the deluge of recent rain and the subsequent saturation of the ground, some plants may show damage, often yellow leaves on the lower part of plants. This occurs both in ornamental and vegetable plants.

• Commonly, yellowness is due to lack of iron or nitrogen in the soil. However, when the soil is saturated with water, oxygen is forced out of the air spaces and the roots suffocate. This prevents them from absorbing nutrients, resulting in the yellow appearance. As the soil dries out, this problem will correct itself.

• Some pests can be hand-picked without using a pesticide. Do not spray if predators such as lady beetles are present. Spraying insecticides early in the morning or late in the day will avoid spraying honeybees and other essential pollinators.