Beware! : Mold & Mildew

Hydroponic gardens are less likely to have mold problems than a soil garden but it can happen. Proper air movement is needed to bring in Co2, which all plants need to grow healthy. It also encourages the plant to draw food and water up from the roots to the foliage. If you do not notice a mold problem right away, than wind or air movement may pick up spores from the mold and transfer it to other plants. Molds can be crop devastators with the average mold spreading quickly in temperature ranges of 60° to 80°F. Most often molds begin in a shady region of your plant or grow room, search thoroughly, better safe than sorry. The best method of control is prevention. For dealing with powdery mildews or even more rare stronger molds, fungicides work well and are commonly used by marijuana growers. Fungicides function in two different ways, they are used for protectants or eradicants, on occasion both. Sulfur can be used, however it only works if it is in the room before the mold problem occurs. Wettable sulfurs that are specially formulated with surfactants similar to those in dishwashing detergent (e.g., Safer Garden Fungicide), are the best sulfurs for your garden. To avoid injuring any plant, make sure not to apply sulfur when air temperature is near or over 90°F and do not apply it within 2 weeks of an oil spray. Other sulfur products, such as liquid lime sulfur or sulfur dust, are much more difficult to use, irritating to skin and eyes, and limited in use. Also available is a fungicide product containing potassium bicarbonate (e.g., Kaligreen) and a fungicide that can be made at home by combining 2-1/2 tablespoons of horticultural oil (Sunspray Ultra-Fine, Saf-T-Side, etc.) in a gallon of water and adding 4 teaspoons of baking soda. This solution is sprayed on plants to prevent and deal with mild powdery mildew infections. Sprays of both potassium bicarbonate and baking soda can injure the plant if sprayed within a two week time period. If baking soda solutions are used in a dirt or soil operation, you must watch the soil around the plant, you may need to remove small amounts and add more. Use Baking Soda sparingly.

If mild to moderate powdery mildew symptoms are present, the horticultural oils and plant-based oils such as neem oil and jojoba oil should be used. Fungicides should generally be sprayed or applied twice, about 5-10 days apart. One effective, and all natural, fungicide on the market today is SM 90. When sprayed on the stem or leaf of an infected plant, SM 90 is an effective agent for treating many molds, mildew, leaf spot, etc. It is also effective against botrytis, blight, fusarium, leaf mold, rhizoctonia stem rot, sclerotinia stem rot and others. SM 90 is prepared from natural plant oils and is completely non toxic to humans, animals, or plants. It is totally biodegradable and environmentally friendly.

Typical symptoms of disease include spots of various sizes and colors, abnormal localized swelling (galls), blights (sudden death of foliage, branches, or flowers), rots (general decomposition of plant tissue), cankers (dead areas on bark or stems which are often discolored and may be raised or sunken), and general dwindling of plant health. Leaves infected with powdery mildew may gradually turn completely yellow, die, and fall off. There are many different species of powdery mildew fungi, most do not need moist conditions to establish and grow, warm conditions are generally ideal. To begin growth, powdery mildew requires living plant tissue, unlike other molds. Most powder molds also grow as thin layers of mycelium or fungal tissue on the surface of the affected region. One good thing about the common molds is that they are sensitive to extreme heat and sunlight, so if you can take an infected plant outside put it in sunlight for a couple days and watch the mold vanish.

One of the most important things to know about fungicides is what they do. A protectant fungicide prevents new infections from occurring, where as an eradicant can kill an existing infection. You may be able to get away with using a protectant so long as the mildew or mold hasn’t gotten out of hand. Protectant fungicides need to be applied no later than the first sign of infection, in 24hrs powder mildew can infect a whole crop.

An eradicant should also be used with the first sign of infection. Never wait to deal with any mold or mildew problem! Remove any infected plants from the grow room if you need to, and always remember to wash your hands after caring for an infected plant. Several least-toxic fungicides are available, including horticultural oils, neem oil, jojoba oil, sulfur, potassium bicarbonate, bicarbonate of soda (baking soda), and the biological fungicides AQ10 and Serenade. With the exception of the oils, these materials are primarily preventive, although potassium bicarbonate has some eradicant activity. Oils work best as eradicants but also have some protectant activity. To eradicate mild to moderate powdery mildew infections: a horticultural oil such as JMS Stylet Oil, Saf-T-Side Spray Oil, Sunspray Ultra-Fine Spray Oil or one of the plant-based oils such as neem oil (e.g., Powdery Mildew Killer) or jojoba oil (e.g., E-rase). Be careful, however, to never apply an oil spray within 2 weeks of a sulfur spray or plants may be injured. Also, oils should never be applied when temperatures are above 90°F or to drought-stressed plants.

Biological Fungicides: Biological fungicides (AQ10 and Serenade) are commercially available beneficial microorganisms formulated into a product that, when sprayed on the plant, destroys fungal pathogens.

AQ10: A parasitic fungus, Ampelomyces quisqualis, that actively attacks and destroys the powdery mildew fungus. The active ingredient in Serenade is a bacterium, Bacillus subtilis, that helps prevent the powdery mildew from infecting the plant. Both products function to kill the powdery mildew organism and are nontoxic to people, pets, and beneficial insects.

Of the horticultural oils, JMS Stylet Oil is the most highly refined and therefore the least likely to damage plants, but it may be more difficult to obtain than the others.

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