(News article for August 1, 2019)
Choosing disease resistant plants is a good way to avoid problems rather than trying to deal with them after they occur. This is true in the case of fruit plants (discussed last week), ornamentals, and vegetables. Resistant varieties are not available for all diseases, but when they are, I suggest that you consider choosing them.
In the case of vegetables, resources like the Louisiana Vegetable Planting Guide and the Southeastern US Vegetable Crop Handbook provide information about which vegetable varieties have resistance to certain disease. Seed catalogs often provide information about disease resistance, too.
There are a number of tomato varieties with resistance to one or more of several common problems. You may recall the article I wrote several weeks ago about causes of wilt in tomato. One cause of wilt that I didn’t mention was Fusarium wilt. I didn’t mention this because it’s not seen all that often in tomatoes these days. Many of the tomato varieties that people commonly grow now – including ‘Amelia’, ’Big Beef’, ‘Bella Rosa’, ’Celebrity’, and ’Florida 91’ – are resistant to one or more races of the fungus that causes it.
People may still run into Fusarium wilt problems when growing heirloom tomato varieties, like ‘Cherokee Purple’ or ‘Mortgage Lifter’. When plants have Fusarium wilt, one side of the plant or of individual compound leaves often turns yellow, while the other side initially appears pretty normal.
Another problem that many tomato varieties have resistance to is the root knot nematode. Nematodes are microscopic worms. Many are harmless or beneficial, but some are parasitic on plants. Root knot nematodes cause swellings, or “knots,” on roots of tomato and other vegetables, like okra and cucumber.
Plants with root knot nematode problems often experience stunting, wilting, or nutrient deficiencies, since the plant can’t move water and nutrients from the roots to the top very well. As with Fusarium wilt, resistance to root knot nematodes is fairly common in modern tomato varieties. Some varieties with nematode resistance include ‘Amelia’, ‘Better Boy’, ’Big Beef’, and ‘Celebrity’.
A final tomato disease for which we can get resistant plants is tomato spotted wilt virus (TSWV). When this disease occurs, it can have a major impact on tomato production. This virus is spread by insects called thrips. It can cause plant stunting and distortion and sometimes results in circular areas of discoloration on the leaves. If the plant makes it to the point that it produces fruit, the fruit may have spots that are lighter in color than the rest of the tomato, giving it a mottled appearance. ‘Amelia’, ‘Bella Rosa’, and ‘Tribute’ are some tomato varieties that have resistance to TSWV.
Cucumbers are another crop for which varieties with a wide range of disease resistance is available. The varieties ‘Dasher II’, ‘Indy’, and ‘Thunder’, for example, all have resistance to several common diseases of cucumbers, including angular leaf spot, powdery mildew, and downy mildew. The first two also have resistance to anthracnose.
Choosing disease resistant varieties is a way to save time and money, reduce pesticide use, and increase your enjoyment of the garden.
Contact Mary Helen.
Many modern tomato varieties have resistance to one or more races of the Fusarium wilt pathogen (Fusarium oxysporum f. sp. lycopersici). When tomato plants have Fusarium wilt, one side of the plant or of individual compound leaves often turns yellow, while the other side initially appears normal. (Photo source: Edward Sikora, Auburn University, Bugwood.org)