Disease prevention relies on a little background knowledge, especially since you’re dealing with a largely invisible enemy. Plant diseases are caused by fungi, bacteria, and viruses These disease-causing organisms, or pathogens, create disease by using portions of the host plant as both home and food. Once pathogens begin to feed, they cause a variety of symptoms. By carefully examining your plants for these symptoms, you’ll be able to get a good idea of what type of organism is causing the problem.
Once you’ve identified the type of disease organism that has infected your plants, you’ll be able to treat it – or at least prevent it in the future. In many cases, you won’t be able to identify the disease organism by species
Fortunately, preventive measures are effective for all types of disease, and organic control measures for each broad group of disease organism generally help lessen the problems caused by all organisms in that group. Therefore, if you at least distinguish a fungal disease from a viral or bacterial one, you’ll be able to choose the proper control steps to take.
Below is the profile on fungi – in order to help you learn more about how this enemy operates so you can mount an effective defense of your garden.
Fungi are responsible for the greatest number of plant diseases, causing rotted tissue, moldy coatings, or spots on flowers, foliage, and stems. So-called fairy rings (ever-widening circles of yellowed grass that appear on lawns) also are caused by fungi. Despite the menace they pose, there are some good fungi, like the ones that transform garden debris into compost
Fungi can invade and rot stem bases, crowns of plants, foliage, flowers, or fruit. They can also cause blighted areas to appear, in which case plant parts wilt and die suddenly, but may only rot afterwards. Other symptoms of fungal diseases include: wilting; spots or blotches on leaves, flowers, fruit, or stems; galls (swelling); moldy or mildewed coating on plant parts; and blistered or curled leaves.
Fungi also cause smuts, which are sooty masses on plant parts usually found on cereals and grasses; scabby areas on fruit or foliage; rust, characterized by powdery blisters – generally red-brown or yellowish – on leaves; and cankers, which are lesions on twigs or bark. If you suspect a fungal disease, use a hand lens to look at diseased plant parts very closely. You may be able to spot the fine, threadlike web that makes up the body of most fungi or see clusters of tiny, spore-bearing stalks.
Some fungi live only on material that is already dead (like the species involved in the composting process). Other fungi that live on dead material are capable of attacking living plants as well. They manage this by releasing toxins that kill plant cells in advance of their spread through the plant Other fungi survive equally well on living or dead material. They attack living plants during the growing season but dine just as happily on dead stalks, leaves, and roots. Many are attracted to bruised, damaged, or stressed plant tissue.
Fungi reproduce by releasing spores. Some spores can germinate within a few minutes of being released from the growing fungus. Others remain dormant until environmental conditions, such as the amount and temperature of water on a leaf surface, signal good growing conditions. Some spores can wait as long as 20 years before germinating.
Swimming spores live both above and below ground, moving through dew or soil water in response to chemical or electrical emissions from host plants. Wind-borne spores can
Since most fungi germinate in high-moisture conditions, good soil drainage is crucial to control. Adding organic matter to improve soil drainage, double-digging beds, or planting in raised beds are all effective ways to improve soil drainage. Good air circulation is also important because it helps reduce moisture on foliage, stems, flowers, and fruit. Space plants so they have ample access to light and enough space so air can circulate freely Avoid working in the garden when foliage is wet to keep from spreading the spores from plant to plant. Try not to wet the leaves while watering, and water early in the day so leaves can dry before nightfall.
When you spot the first sign of a fungal infection, remove all plants or plant parts that show symptoms. If you have a newly built hot compost pile, one that will heat to 160F, you can bury infected plant parts near its center to kill all traces of the fungus and avoid reinfecting the garden. Otherwise, dispose of infected plants in sealed bags in the trash, or bum them. If the fungi are ones that live or spread through the soil, like club root of cabbage family plants, dig and dispose of the infected soil as well.