COMMON PROBLEMS AND DISEASES IN THE GARDEN
Nothing can take the fun out of gardening faster than disease-ridden plants. The most prudent and useful advice is to start with plants that have good disease resistance. Other things that can be done to help control problems include the following:
- Rotate families of vegetables in the garden regularly
- Keep insects under control
- Use mulch to help keep in moisture
- Avoid overhead watering and splashing water on bare dirt that ultimately ends up on the leaves and stems of your plants, possibly spreading disease
- Keep the garden area clean by removing yellow leaves and over-ripe fruits regularly
- Never smoke in the garden as disease can be transmitted to your plants by the use of tobacco products
Common diseases to be on the look out for include the following:
Anthracnose — Caused by a fungus, Colletotrichum orbiculare, it can attack and affect many garden plants, especially cucumbers, cantaloupe and tomatoes. Look for yellow spots and water-soaked areas on leaves and fruits. It is most prominent in the hot temperatures and humidity of August.
- Progression: The yellow spots are the first sign of infection, followed by the areas turning brown, and then leaving ragged holes on the leaves within the spots. Affected fruits will have circular, sunken brown spots that will eventually turn black. Finally the fruit will shrivel.
- Control / Cure: Don’t work in the garden when the plants and leaves are wet. The use of fungicides on a regular schedule is recommended for good control. Any infected plants and fruits should be removed from the garden and buried deeply to prevent spreading the disease. Anthracnose can overwinter in the seeds of infected fruit, so good garden clean-up is encouraged.
Bacterial Wilt — Mainly affecting squash and cucumbers, this is caused by a bacterium, Erwinia tracheiphila, which clogs the vascular system of the plants. Watch for wilting leaves and branches, and if you know the plant has adequate moisture, suspect Bacterial Wilt. This is spread by the cucumber beetle. They can overwinter and emerge in the spring, carrying the bacterium in the digestive tract. The beetles eat the leaves, exposing the plant to their excrement that infects the plants.
- Progression: At first it appears that the plant is just dry. Sometimes only a few leaves will wilt, but it soon progresses to the whole plant.
- Control / Cure: The best control of the beetles is insecticide sprays. Trap and companion plantings can help with repelling and control. The use of fiber row covers is an excellent way to control the beetles, but you need to remove them at pollination time. Remove any affected plants and dispose of them away from the garden area. An absolute must is to practice crop rotation!
Powdery Mildew — Caused by a fungus, it can affect many plants, especially your vine crops. Very fast moving, it can infest your plants in as little as 3 days. Hot, dry days and cool, humid nighs can contribute to the spread. As the name implies, it looks like someone has sprinkled powder on the plants. Crowded plants with poor air circulation are the most susceptible. There are many different types of powdery mildew, each being host specific (each affects only a certain type of plant) but each will multiply under the same conditions. Spores are produced continually and released into the air.
- Progression: You’ll see small patches of white or gray on the top of the leaves or stems of the plants, but it can also be found on the underside of the leaves, on flowers, and even on the fruit. Without treatment it can engulf the entire leaf surface and even spread to the blossoms and fruit. Although rarely fatal to the plant, it can reduce photosynthesis by covering the leaves, or because the leaves can fall off prematurely.
- Control / Cure: Plant in full sun with plenty of room for good air circulation. Improve air circulation by pruning some of the thicker branches or leaves of the plants. Always water from below, avoid getting the leaves wet. Remove and infected plant parts and do not add to your compost pile. Do not fertilize until you have the mildew under control. It thrives on young, tender new growth. Apply a fungicide according to label directions, or use a home remedy. Many recipes are available on the internet and can be quite effective in prevention and control.
Verticillium Wilt — Caused by a soil-borne fungus, it can affect a numer of different vegetables in the garden, including tomatoes, peppers, potatoes and eggplants. If your garden space is affected, use a long rotation period (4-6 years) avoiding the above plants in the area. Also avoid strawberries and raspberries, which are highly susceptible.
- Progression: Leaves wilting in the hottest part of the day and recovering at night, leaves turning yellow and drying up, never appearing to wilt, and sometimes only one side of stem will turn brown and die. Usually will start with the lower, older leaves, and as the plants ability to take up water decreases from vascular damage, the plant will die.
- Control / Cure: Practice long crop rotation periods, keep areas as weed-free as possible (some weeds carry the fungi), feed appropriately for strong, healthy plants and when purchasing plants, look for disease-resistant varieties. Remove old plant material at the end of the season and destroy. Do not dispose of in the compost pile, you could spread the fungus.