Original post @ Organic Tomato Garden Tips to read full article, in addition to Using Hydrogen Peroxide with added information.
Early Blight"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.
Verticillium Wilt"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."
Bacterial Spot"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."
Bacterial Canker"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"
Aphids"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.
Hornworms"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... Another remedy is to sprinkle flour on the tomato plants."
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."
Blossom end rot
"A water-soaked spot at the blossom end of tomato fruits is the classic symptom of blossom-end rot. This relatively common garden problem is not a disease, but rather a physiological disorder caused by a calcium imbalance within the plant." Some gardeners suggest using eggshells because it contains calcium, but other gardeners protest that using eggshells is not useful because the shells take time to break down. In turn, they suggest keeping consistent soil moisture around the plant. Frequency or amount of water is not key, just consistency. Additionally, "Excess ammonial types of nitrogen in the soil can reduce calcium uptake as can a depleted level of phosphorus" according to one user at a garden forum here. This user also suggested Tums tablets, which I would consider Calcium vitamins as a handy "supplement" to the plant/soil if you have nothing else on hand.
Companion 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. 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 Spray"Garlic and pepper is an all-purpose bug spray for common tomato plant problems such as aphids and hornworms. Its strong odor keeps many insects away. This spray also stops mildew.
Organic Fungicide"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 as a preventative or when blight problems have already developed. An effective mixture is baking soda, vegetable oil, and Castile soap. Another popular organic fungicide is an apple cider vinegar and water mixture."
*Peroxide is another useful ingredient in the garden regarding health and prevention. This is because peroxide "works by releasing oxygen. It acts as an oxygen supplement for plants. It seems to really support both good health and strong growth for plants.
Hydrogen peroxide can also help with soil fungus: it aerates the soil, and it is anti-fungal. (It is also anti-bacterial)" according to Using Hydrogen Peroxide. Additionally, peroxide works as a General fertilizer, either in plant water or sprayed on foliage. Secondly, peroxide helps sick plants, which can be applied by using a Spray bottle on the leaves and add to water. Mold or fungus on plants or in the soil can be controlled by using Hydrogen peroxide on plants or in the soil. If you’ve got mold on the plant, spraying the leaves is probably best. Third, Hydroponic gardeners often use peroxide to feed plants, by adding it to the watering system. Also, a Peroxide Spray on tree cuts, helps prevent infection. Peroxide as a spray in the greenhouse controls mold and mildew. Sprouting seeds before planting using water and peroxide that seeds soak in for seeds to sprout faster and grow stronger. Rooting cuttings appreciate the added peroxide in water, if you’ve put the cuttings directly into water before planting. Or, if you’ve put the cuttings into soil or medium, use peroxide in the water you’re using to water the cuttings with.
*Epsom salt as a fertilizer for tomatoes as well. A healthy plant that is more mature will be less susceptible to pests and/or pathogens. Overall, 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.
Compost Tea Spray"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. Compost is rich in microorganisms that have anti-viral and anti-fungal properties. Dilute the compost/water mixture and let it sit for 1 week before use to ensure that plants are not burned".
Beneficial Insects"Ladybugs, praying mantis, and lacewings are known as “beneficials” and they are a very effective organic pest control for tomato problems. They eat the insects which chew and destroy tomato plants, such a flea beetles and aphids."
*You can attract beneficial insects through creating their ideal environment. Recently I posted examples of ways other gardener made "bug hotels" that attract these insects, here: Beneficial insect/bug hotel ideas