Summer tomato diseases and problems
Wednesday, June 11, 2014 1:00 AM
The phone is ringing! There is a tomato plant in trouble somewhere! The number one vegetable for home gardens is under attack.
In spite of progress that has been made with disease resistance, tomatoes are still are plagued with many diseases. And when gardeners grow the older, tastier varieties that do not have any disease resistance, problems only get bigger. Insects and non-disease problems are also adding to the difficulties.
Following is a short summary of tomato diseases and other common problems seen in home garden tomatoes and how to reduce their impact.
Tomato leaf curl is a physiological disorder related to the hot, dry weather. This condition involves an initial upward cupping of the leaves, followed by an inward roll. In severe cases, the leaves roll up until the leaflets overlap. Symptomatic leaves become thickened and leathery. Symptoms typically appear first in lower leaves but may spread to the entire plant, depending on the severity of the condition.
Leaf roll is more commonly associated with indeterminate varieties of tomato, such as "Early Girl" and "Big Boy", rather than determinant types such as "Celebrity." In most cases, the condition is temporary and will have little or no affect on plant growth or yield.
Aphids and whiteflies are two insect pests showing up together this year. Aphids are small soft-bodied insects that can be red, green, or black in color. Whiteflies are very small (1/16 inch long) and white in color and when you bump a plant that they are on; they fly.
Both are sucking insects that like the nice juicy tomato plants. These insects are controlled by regular sprays of malathion insecticide.
Blossom-end rot (BER) is familiar to anyone who has ever grown a tomato. BER is characterized by a leathery, brown, or black spot on the bottom of the fruit. It generally occurs on the first fruit cluster.
BER is a physiological problem associated with soil calcium and watering practices. BER is caused by a lack of calcium in the developing fruit that causes the end of the fruit to die creating the characteristic spot.
What can you do to prevent it? Make sure soil calcium levels are okay by getting a soil test. The next most important control measure is to maintain optimum soil moisture. When tomatoes experience the slightest bit of drought, BER may result. Using mulches will usually significantly decrease BER.
Tomato spotted wilt virus has been the ruin of many tomato patches. The disease, carried by thrips, begins with dark spots that form on leaves and spread to stems, forming cankers.
The growing tips die back and the growth of the plant is stunted. Additional symptoms of the disease include cupping and rolling of the leaves that usually turn purple along the veins. There is no treatment for the infected plants and they should be discarded.
If the fruit are set prior to infection, they may be distorted or develop blotchy orange ring spots as they ripen.
Tomato varieties such as "BHN 444" (aka "Southern Star"), "BHN 644", "Amelia", "Top Gun, and "Crista" are resistant to the spotted wilt virus. If you did not use a resistant variety, a possible retro-prevention is to put aluminum kitchen foil on the ground around your tomato plants.
The reflected light often confuses the thrips and keeps them from landing on and infecting the plants. Weekly spraying of malathion insecticide will also slow the spread of the thrips.
Just about every tomato plant grown in Mississippi has the potential to become infected with early blight. Symptoms of early blight include dark brown, irregular spots on the lowest, oldest leaves.
As spots mature, they develop concentric rings, usually surrounded by a yellowish area. Early blight will infect leaves, stems, and fruits. This disease can be controlled by weekly applications of fungicides containing chlorothalonil or maneb.
This is only a partial list of diseases and problems that attack tomatoes. So, do you still want to grow tomatoes? If so, do it right. Choose varieties that are resistant to some of the diseases.
Look for the letters V, F, N, or TMV after the variety name or state they are resistant to the spotted wilt virus resistance. Plant on silver colored mulch. Spray regularly for insects and fungal diseases. Maintain soil moisture and fertility.
Sounds like a lot of work, but when you put that first vine-ripened tomato of the summer in your mouth all that is forgotten.
You also will be the envy of your neighbors who did not give 100 percent in their tomato growing and now have to come to you for those wonderful summer fruits.
It is not too late to get homegrown tomatoes this year; fall planting in just around the corner.