By AMY DISMUKES
Living in Tennessee guarantees heat and humidity, which in turn guarantees a high insect and disease pressure.
Tomatoes get hit especially hard, with the possibility of a myriad of pests
attacking though out the growing season. If you can stay on top of any
potential problems and address the issue promptly, you’re sure to have a bountiful and delicious season.
A few of the THUGS. Early Blight is one of the most common diseases of
tomatoes in Tennessee and is caused by the fungus Alternaria solani. It
affects all parts of the plant and is spread by wind and splashing water. Like
most fungal pathogens, it favors warm, wet weather and can overwinter in
crop debris. Early blight is seen early in the season, hence its name, often
striking after a period of heavy rainfall. Generally, the spots will develop on
the lower leaves first, which will then turn yellow and drop. You can
differentiate early blight from other tomato pathogens by the spots, which
are dark brown with concentric rings, almost like a bull’s eye. The spots on
infected fruit often begin near the stem.
Septoria Leaf Spot, caused by the fungus Septoria lycopersici, is a common blight of tomatoes and is capable of destroying leaf tissue very quickly. Just as early blight, Septoria develops very quickly in rainy weather and starts at the bottom of the plant, traveling upward to infect new growth.
Septoria is characterized by small, dark, circular spots that will eventually develop grayish-white centers. This disease is differentiated by target-like leaf spots of early blight the tiny black specks (fungal fruiting bodies) that develop within the light centers of the spots.
To control both Early Blight and Septoria leaf spot, a combination of cultural and
chemical practices are recommended. Rotate your crops every few years by alternating planting locations of tomatoes and other solanaceous crops within your garden. Keep the area clean and remove any diseased plant materials from the plant and surrounding soil (do not compost). Water only at the root zone
and stake or cage plants to provide adequate air flow. Fungicide sprays containing chlorothalonil should be applied every 7-14 days, depending on the amount of rain. Copper fungicides are an organic option, and can provide some control, but tend to stop working as efficiently unless rotated with another
Now for some of the SLUGS. Not all plant maladies are caused by a pathogen or insect. Genetics and most often, the environment, can cause confusing symptoms like catfacing, blossom end rot or green shoulders. Most folks experience the immediate ‘need to spray’ reaction when an abnormality or imperfection is observed, however, make sure you know what you’re dealing with before you pull out the chemicals … a fungicide won’t control a calcium deficiency.
Tomato catfacing is a physiological disorder that results in abnormal cracking, zippering and dimpling on tomatoes and other fruits, somewhat akin to a small cat’s face. It is the abnormal development of tissue affecting the ovary, which results in the flower and then the fruit, to become malformed.
The exact cause of catfacing is uncertain but seems to correlate with unfavorable growing conditions that result in poor pollination, and is more prevalent in heirloom varieties. Temperatures below 60⁰ for successive days when plants are immature coincide with catfacing. Physical damage to the blossom can also cause catfacing. It’s also more prevalent on large-fruited varieties, susceptible to tomato fruit catfacing deformity. Although fruit puckered by catface isn’t attractive at the commercial level, it doesn’t affect the taste and can be safely eaten.
All in all, and regardless of the effort we put into it, our tomatoes sure are a special treat. Keep your garden pest and pathogen free by being aware and proactive, acting fast if a problem should arise. ENJOY!
“A Home Grown Tradition” is written by Amy Dismukes. Amy is the UT/ TSU Horticulture Extension Agent for Williamson County, Tennessee, and is a graduate of Auburn University, where she received a Bachelor of Liberal Arts, a Bachelor of Science in Horticulture and a Master of Agriculture in Plant Pathology & Entomology. She provides educational training for both homeowner and commercial clientele regarding issues concerning horticulture, conducts site visits throughout the county to diagnose and resolve issues with insects, plant diseases, soil and weeds, and is a frequent guest speaker for professional, garden and horticultural associations and commercial pesticide workshops/conferences. Amy also coordinates the Williamson County Master Gardener Program. Please email any questions or concerns to Amy at firstname.lastname@example.org.
This column includes research-based recommendations from Tennessee State University and the University of Tennessee. Extension is committed to affirmative action, equal opportunity and the diversity of its workforce. Educational programs serve all people regardless of race, color, age, sex, religion, disability, sexual orientation or national origin.