There seem to be many questions about plant diseases; sometimes ones without marks on the leaves or other lesions. Have any of you had bacterial diseases yet? Here is one way for testing for a bacterial disease in your dying plant.
Remove a diseased plant and slice through the stem with a sharp knife. Then place the stem into a clear glass filled with clear water. leave it for a minute or two. Then hold the plant against the light. If it is a bacterial disease, bacteria will ooze out of the wound. You will quite clearly see a transparent or milky stringy substance coming out from where you made the cut.
There are also many other soil-borne diseases. Many of them are fungal diseases where the mycelium of the fungi grow inside the cells. Most fungi thrives in moist warm conditions. Therefore drainage is quite important in your garden. Soil borne fungi like pythium and phytophthora will infect plants through their roots or around the crown of the plant when free water is around. Typical symptoms include general wilting and yellowing of the whole plant. Raised beds can help with drainage.
Don’t overhead water your plants unless you have no other choice, and if you do, water early enough in the day to allow the water to evaporate again before night comes. Ensure good air circulation (one good reason for having 3 1/2′ aisles!) between plants. For example, prune tomatoes and stick to correct plant spacings as shown in the Mittleider resources.
An integral part of disease management is to REMOVE diseased plant materials from your garden site! If you are serious about getting rid of the disease, burn the diseased plant materials. Fungi are designed for survival; during adverse conditions they produce survival or overwintering structures that can survive for a very long time until conditions improve again. These can survive on old and dying plant materials and other WEEDS in the garden. Therefore the big emphasis on removing weeds promptly (besides serving as a scrumptious food source for cutworms and other insects).
When you have handled diseased plants with scissors, a knife or other implement, you should sterilize it by spraying it with some ethanol, or other alcohol source like denatured alcohol, before using that tool on healthy plants again. This way you stop the spread of disease between plants.
Diseases and pests are here to stay, and they can take over our lives (gardens) unless we subdue them! Promptly remove leaves that show signs of disease. Example: Older tomato leaves (closest to the ground) usually start showing leaf lesions as the season progresses and disease pressure builds up in the area. Remove these promptly to stop the spread to other leaves and plants.
Insects are sometimes the carriers of viral diseases. By keeping insect pests under control you may thus control plant diseases! However, some insects are good, like lady bugs, which have a healthy appetite for plant aphids, and so too do their larvae. Bees are our most famous pollinating insect. If you spray for pests in the garden, do so early or late in the afternoon when bees are not forraging for nectar and pollen.
We work very hard to grow a delicious variety of veggies in our gardens. I have thanked Dr Mittleider and Jim many times over in my mind when I have relied so much upon my home-grown veggies in times of need. I have never had a failed crop when following these “recipes” to the letter. By ensuring cleanliness in our garden and following a few other important steps we can even subdue the pests and diseases.