It’s easy to see why the tomato is a top choice among home gardeners. Plants adapt well to most soil conditions, they are perfect for small garden spaces, and the tomato itself has many uses. Tomatoes are a high crop yield so just a few plants are necessary to satisfy the needs of most families for the entire season. Tomato plants are relatively easy to grow, but they are susceptible to a few ailments.
Caused by a fungus Alternaria solani, early blight is also known as target spot or alternaria leaf spot. Signs of early blight are loss of leaves on the lower part of the plant and brown or black spots that are 1/4 to 1/2 inch in diameter that appear on lower leaves. Spots often merge and form odd-shaped blotches and may look like a target. Leaves will fade to yellow and dry up. Early blight often attacks the tomato as well, leaving large black concave areas on the tomatoes. Warm damp weather helps spread early blight. Fungicide is used to control early blight. Follow manufacturer’s instructions when using any fungicide on your plants (even the organic ones have to be properly applied).
The fungi Venticillium albo-atrum and Verticillium dahlie are the cause of verticillium wilt. Small yellow patches appear on the lower leaves of the plant and, eventually, as the disease spreads upwards, leaves turn yellow, wither and drop. Verticillium wilt also causes the internal browning of the stem near the soil line. Infected plants can survive but their growth is often stunted and their crop yield is lower. Controlling verticillium wilt is difficult; no fungicidal treatment has been effective. The best way to prevent verticillium wilt is to choose tomato plants that are not susceptible to the disease. Look for tomato plants or seeds that are labeled “V” for verticillium-resistance. The Better Boy, Big Beef, Roma and Early Girl are a few varieties of tomato that resist verticillium wilt.
Bacterium Xanthomonas campestris pv. vesicatoria causes bacterial spot. This disease appears as brown spots on the leaves and stems of the tomato plant. The splotches are about 1/8 inch across and feel slightly slimy to the touch. As the spots begin to grow they often appear to be surrounded by a yellow halo. Once spots become abundant, they will grow together and cause the leaves to turn brown and wither. Bacterial spot can affect the fruit of the plant. Black dots will appear on the tomato and will enlarge to 1/4 to 1/2 inch in width and become sunken, gray and scab-like. Keep areas around tomato plants weed-free to help reduce the chance of bacteria growth. Fungicide is effective in controlling bacterial spot. Follow manufacturer’s instructions when using fungicides on your plants.
Plants infected with bacterial canker often appear to have the disease on only one side. Eventually the disease does spread to the entire plant. Caused by a bacterium Clavibacter michiganesis subsp. michiganesis, bacterial canker can cause extensive damage to your tomato crop. Young plants will suddenly wilt and older plants will experience browning along the edges of their leaves. In rare occasions, the stems of the plant will develop cavities or brown cankers. Raised white spots may occur on tomatoes, sometimes called birds-eye-lesions, and the white spots will turn brown as it ages. Control bacterial canker by planting disease-free plants and keep areas weed free to reduce chances of bacterial growth. Copper spays have little effect on the bacterial canker and, most likely, will not stop the spread of the disease.
Septoria Leaf Spot
Septoria leaf spot is caused by Septoria lycopersici. The first symptoms are small, water-soaked spots. The spots grow to about 1/8 inch in diameter, then develop grayish-white centers. The edges then turn dark. The spores of this fungus are spread through rain and from watering from above. Eventually, the leaves turn yellow and fall off. While the infection can invade the plant at any time, it is most commonly seen after the plant sets fruit, according to the University of Iowa. Control septoria leaf spot by planting healthy plants with the proper amount of space between them, watering at the base of the plants, watering in the morning, removing dead and decaying branches, and keeping any fallen plant debris cleaned up. Control existing infection with fungicides.
One of the most common pests on tomatoes is the aphid. Aphids suck the sap of the plant causing misshapen foliage and fruit. Introducing beneficial insects into the garden can help this problem. The natural predators of aphids are laceywings and ladybugs. Both can be purchased by mail order or at some garden centers.
Hornworms are a green caterpillar with small black spots and two protruding antennae on their heads. They eat foliage and the tomatoes and can do a lot of damage before you find them. The best defense against hornworms is to go in your garden often and pick them off the plants. Put them in a bucket of soapy water. Another remedy is to sprinkle flour on the tomato plants. They eat it and then die.
Cutworms and whitefly
Cutworms damage tomatoes by cutting the stems. If you see this damage on your plants use wood ashes on the ground around the stems. Another common pest is the whitefly, which makes the tomato leaves yellow and distorted. Laceywings and ladybugs are also effective for this insect, as well as spraying with garlic oil or using yellow sticky traps.
Go organic for pest control
The Arlington Organic Gardening Club says “organic insecticides are more effective controlling pests and are safer and easier to use. Take your chemical pesticides to your city’s next hazardous waste collection day and use the following techniques for controlling unwanted insects in your home and garden.” Pest control for tomatoes begins with creating nutrient-rich soil so plants are strong and resistant to disease. Add organic compost to soil before planting.
Traditional gardening wisdom teaches that certain plants grown together create mutual strength and disease resistance. Companion planting is one way to create a disease-resistant tomato plant. The National Sustainable Agriculture Information Services provide charts and lists of companion planting. Tomatoes become more disease free and pest resistant when planted near onions, nasturtiums, marigolds, asparagus, carrots, parsley, and cucumber. Basil repels whiteflies. Dill and borage repel hornworms.
Organic Insect Sprays
Organic pest control sprays do not cause harm to children or pets that come into contact with them. They leave no chemical residue on the tomatoes. Many gardeners prefer to make their own bug sprays out of common household ingredients, as you can see one example in the video below. There are many types of and recipes for organic sprays to control pests. Garlic and pepper spray (made like a tea) is a common all-purpose pest deterrent for many common tomato plant problems such as aphids and hornworms. Its strong odor keeps many insects away and it also helps stop mildew and fungus. You can increase its power by adding plants that are deadly to insects such as wormwood to the mix. Simple organic soap is also incredibly effective, just add a teaspoon or two to each bottle you make and shake it up.
Baking soda has been found to have fungicidal properties. Baking soda spray is effective for tomato blight, powdery mildew, and as a general fungicide. Use it as a preventative or after blight problems have already developed. An effective mixture is baking soda, vegetable oil, and Castile soap. Apple cider vinegar and water mixture is another popular organic fungicide, and many find that a simple milk and water spray is quite effective against tomato virus such as the cucumber mosaic virus. And again, tomatoes love their calcium, so make sure you amend your soil with a dose of agricultural lime each year so that they can fight off most fungus issues on their own.
Keep blight and other pathogens away from tomato plants with a compost tea mixture to spray on affected leaves. It is also used as a soak around the base of the plant and works wonders as a fertilizer. Compost tea is rich in microorganisms that have anti-viral and anti-fungal properties. You can make it by simply diluting some “worm tea” from your bin, otherwise you can brew it by taking a small bag full of aged compost (not fresh stuff that is just starting) and soaking it in a large bucket with an air pump keeping the mixture as oxygen rich as possible.
Ladybugs, praying mantis, lacewings, wasps, assassin bugs and the like are known as beneficial predators as they eat the pest insects which chew and destroy tomato plants, such a flea beetles and aphids. Ladybugs and preying mantids can be purchased at most garden centers or by mail order. You can also attract beneficial insects to your garden by building an insect hotel for them to live in.
Free PDF Download on – Companion Planting: Basic Concepts & Resources
Sources: Garden Guides, Guardian, Mother Earth News
About Fritz Kreiss
Fritz Kreiss is the founding head of Occupy Monsanto. He has a history in natural health, nutrition, herbal medicine, Eastern Medicine, acupuncture, kinesiology, physiology, and many years of practice as a professional massage therapist and teacher.