Houseplants Under Lights

Lesson 4: Proper Plant Selection and Care

Diseases

The most common diseases are discussed below along with some methods to cure the problem. If you choose to use chemicals in your home, follow the package directions carefully. Personally, I would rather lose a plant than use poisons inside the house. Always be sure to properly identify the disease and the best solution before applying chemicals. Using the wrong chemicals on a disease (or pest) may lead to resistant diseases.

Common Plant Diseases

Powdery mildew: White or gray patches on the stems, flowers or leaves of a plant. High humidity, overwatering, or lack of air circulation around the plants causes this. One solution is to simply fix the causes of powdery mildew by correcting the cultural problems listed. Yet another way is to treat it with a commercial spray made for fungus diseases. Some gardeners prefer to make their own spray by combining a gallon of water, 1-3 tablespoons of baking soda, and a teaspoon of liquid soap. Spray the entire plant. Let the plant dry without rinsing.

Stem or Crown rot: The stems and crown (where the leaves meet at the base of the plant) become mushy or slimy. This is frequently caused by low temperatures and wet soil. The best solution is to cut out the affected parts of the plant and repot the remainder in a quick draining soil. Be sure you wash your hands thoroughly before you handle any other plant in your collection or you will spread the disease throughout your entire collection.

Sooty mold: This is a black mold that grows on the honeydew secreted by sucking insects such as scale, mealybugs, aphids and whiteflies. You only have this problem if an insect attacked the plant first. Wash the plant in the shower or sink. Use something like Safer™ soap spray or make your own soap spray with a tablespoon of Ivory Snow™ liquid dishwashing soap mixed in a gallon of water.

Green slimy growth on soil: Algae occurs whenever soil is not allowed to dry out partially between waterings. Normally, it doesn't hurt the plant and just looks unsightly.

Rust: Pelargoniums (called "tender" geraniums in the United States) may develop brown circles on the underside of their leaves. These rings are formed from the spore of the rust fungus. Sometimes improving air circulation will help. Unfortunately, the only guaranteed solution known today is to simply burn the leaves and plant. You don't want this to spread to your entire plant collection.

Damping off: Primarily affects seedlings. This is caused by a fungus that attacks the roots and stem bases of the young seedlings. They suddenly collapse. Using sterilized seed media is the best solution. You may also treat the seed media with a fungicide before planting the seeds.

General Disease Treatments

I suggest you try A plant soap spray or neem oil before resorting to other chemical solutions. These are the least likely to cause resistant problems. Another common solution is 1 teaspoon of Ivory (or other mild soap) in a gallon of water. Some are using baking soda (recipe varies from 1 teaspoon up) in a gallon of water. Either solution is then sprayed on the plant.

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