Fungus, Mold, Mildew and Other Plant Diseases

Fungi – the plural of fungus – are distinguished from bacteria by their size and the fact that they have cells with distinct organs, like cell nuclei and mitochondria, the food-manufacturing cells in plants.

They are scientifically divided into three categories: yeasts, molds and mushrooms. All thrive in damp conditions. Unfortunately, drying out your garden by not watering for a week will not kill them, as fungi have a remarkable ability to survive drought in spore form (a simple, reproductive structure).

Fungi are a serious plant problem, producing diseases like mildew and rust, but they also have a beneficial side. In the roots of plants, they form mycorrhizal, or symbiotic, relationships, helping plants take up nutrients from the soil and defending against other, harmful fungi and insects. This makes them useful as biological (rather than chemical) weapons in large-scale gardening, like greenhouses, forestry and food production, because chemical fungicides wipe out both bad and good fungi.

Mildew is a form of mold. Most gardeners see it as either powdery mildew (on roses) or downy mildew, most often seen on grapes and vine-like vegetables. Powdery mildew is an obligate parasite, like a virus, and can’t survive without a host. This is not helpful to know if you have a prize Therese Bugnet cultivar dying in your rose bed, as you’re not likely to pull it up and burn it just to get rid of mildew.

Garden stores sell fungicides, but remember when using them that they can be lethal, both to humans and other, beneficial fungi. If improperly used, they can even kill the plants they are meant to help. Wear gloves and safety glasses, cover your arms and other exposed skin, mix the formula precisely as the manufacturer directs, spray or spread on a warm day when there is no chance of rain for at least 48 hours, and mark, safely store, or dispose of all containers used to mix fungicide. Do not use cooking utensils unless you plan to throw them away afterward. Washing will not remove all residue; dishwashers spread the residue. Wash off any spray on your skin under the garden hose, and again inside,with soap .

There are some ‘safe’ fungicides – like neem oil – sold as organic fungicides, and organic gardeners swear by them. Overall, they require more applications and are not as immediately effective as chemical fungicides. The advantage is they will not kill you, your family, your pets, or the honeybees that pollinate flowers and food crops. If you have the time and patience, by all means use them. Another interesting fungicide I discovered in my years of gardening is one part cow’s milk (non-pasteurized) in 10 parts water. Another is a coffee solution, one part very black coffee to 10 parts water. You can also use baking soda (one tbsp. per gallon), a drop of mild detergent like Ivory (make sure there are no additives), and a drop of vegetable oil to bind it to the leaves. You can also use white vinegar (1:3) in water. This probably works because vinegar alters pH, and pH is a significant factor in plant disease.

Fertilizers with potassium will remedy that deficiency. Phosphorous is required by plants in order to achieve photosynthesis. It also helps plants develop adequate root network. Symptoms of phosphorous deficiency include yellowish leaves, and red stems. Without magnesium plants will not be able to absorb light energy, also it would be unable to neutralize acids, or toxic elements. Without iron plants leaves will appear pale and sick looking. Boron is essential for production of seeds, and it helps plants to pollinate. When boron is deficient the plant will look like it has been burnt. Zinc is required for the growth of plants, and without it the plant leaves will appear whitish. It is important to note that all of these issues could be rectified by the application of complete fertilizer. But there are all essential for the appropriate development and ripening of crops and plants in general.