Wednesday, May 26th, 2010
While the gardener hopes for disease-free plants, multitudes of organisms are ever present and merely biding their time for the appearance of the right conditions and host.
Damping-off is likely the most discouraging problem for the gardener. Although it can occur any time during the growing season it generally attacks seedlings just when they seem to be getting off to a good start.
Damping-off is caused by fungi living right at the soil line where air meets the moist soil’s surface. If soil is kept continually damp the fungi attack the seedlings causing constricted stems at or immediately below the soil’s surface. The young plants fall over at the soil line and die.
Prevention is the only remedy. Allow the soil surface to dry out between waterings. If soil remains moist for a long period of time sprinkle the area around the seedlings with ground cinnamon. Cinnamon is a natural fungicide. The gardener may also make use of another natural fungicide, chamomile. Brew weak chamomile tea, let it cool and use around seedlings.
Mosaic virus robs plants of their genetic organization, diverting energy to themselves. This virus primarily attacks summer and winter squash, gourds, cucumbers, watermelons and pumpkins although it also affects beans, peppers and tomatoes.
The virus causes abnormality in plant growth. Leaves look mottled or distorted and crinkled. They twist up or show bubbles. Often the affected plant will have leaves with yellowish spots on them. The fruit of affected cucumbers can have a variation of mottled light and dark green areas, sometimes paling almost white. Other fruit in the curcurbit family can be blanketed with warts or have skin that is faded, white and smooth. Although this virus may not kill the plant the fruit will taste so bitter that it will be inedible.
Mosaic virus overwinters in garden debris and a number of weed plants. Be sure the garden is scrupulously cleared out after the growing season and reduce or eliminate weed growth near food plants. Aphids and cucumber beetles also spread the virus when they feed from plant to plant. Eliminating these pests will go a long way toward preventing the virus from entering your garden.
Botrytis blight or rot is a fungal disease that affects a number of vegetables and fruits. Among its host plants are asparagus, beans, beets, carrots, grapes, lettuce, onions, peppers, potatoes, raspberries, tomatoes and strawberries. The infection usually occurs when cool rainy or drizzling spring and summer weather lasts for several days. Botrytis rot can infect all parts of the plant except the roots. It appears as a mass of silver-gray spores on dead or dying plant tissue. Heavily infected plants release the spores as a dust that can be spread to other plants. The disease spreads most rapidly on wet or humid days and rain splatter also causes new infections.
As with other diseases, prevention is the best control. Inspect the plants often, watching for any infestation, blighted leaves or dead plants. Wait until the plants are dry before taking steps to sanitize them. Carry a paper bag with you when inspecting the plants. Remove infected plant material or the entire plant and place it in the bag to be thrown in the trash or burned.
Avoid overhead watering or misting which also provide favorable conditions for infection. Give plants plenty of space between them to promote good air circulation and allow the plants to dry out quickly, not giving botrytis the moist, humid conditions it needs in order to prosper.
Another fungal disease, powdery mildew, coats the leaves in dusty white or grey powder. Leaves are usually first attacked on the underside and then the mildew moves around to the top of the leaf, eventually covering the entire surface.
Sodium bicarbonate (baking soda) has proven to be extremely effective as an antifungal in treating active botrytis and powdery mildew. Add 1 ounce of baking soda to 1 gallon of water and spray the solution on the affected plant. Caught early, the disease can be halted and the plant saved.
Feeding all plants with finished compost or compost ‘tea’ foliar spray helps to strengthen their immune system, allowing the plants’ own defensive structures to ward off many debilitating diseases.
Vegetable & Garden Fungicide
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