Steneotarsonemus pallidus Cyclamen mites infest several plants, including azalea, begonia, cyclamen, gloxinia, ivy, kalanchoe, schefflera, and African violet. This very small mite cannot be seen with the naked eye. It feeds on new growth, causing it to be stunted, discolored, and curled. Buds fail to open. The female mite lays her eggs on leaf surfaces. The young crawl about the same plant or other plants, where they feed in the buds and cause damage. These mites are favored by high humidity.
Discard severely infested plants. Isolate mildly infested plants. Apply an insecticide labeled for this pest, following label directions. Soak pots from which infested plants have been removed for 30 minutes in a mixture of 1 part household bleach to 9 parts water. Wash the area where pots were sitting with the same dilution of household bleach. Avoid working in the outdoor garden and then on indoor plants without washing up and changing clothes in between.
Several species of this common insect feed on African violet. Mealybugs damage plants by sucking sap, causing leaf distortion and death. The adult female mealybug may produce live young or may lay eggs in a white, fluffy mass of wax. The immature mealybugs, called nymphs, crawl all over the plant and onto nearby plants. Soon after they begin to feed, they produce white, waxy filaments that cover their bodies, giving them a cottony appearance. As they mature, they become less mobile. Mealybugs cannot digest all the sugar in the sap, and they excrete the excess in a fluid called honeydew, which coats the leaves and may drop onto surfaces below the plant.
Separate infested plants from those not affected. Apply an insecticide labeled for mealybugs. If only a few bugs are present, wipe them off with a damp cloth or with cotton swabs dipped in rubbing alcohol. Inspect new plants thoroughly before putting them in the house.
This condition is causes by excess salts on the pot rim. The salts kill the plant tissue where it comes in contact with them. The salts are usually fertilizer, but may be other salts if hard water is used. Dissolved salts in the soil migrate toward the points where water evaporates from the soil and pot, primarily the pot rim. As the water evaporates from the surface, the salts it carries crystallize there. Eventually, the concentration becomes high enough to kill plant petioles and leaves. Excess salts can accumulate if too much fertilizer is used, or if the soil is not leached regularly.
Pinch off the damaged leaves. Flush the soil several times with tepid water, allowing the excess to drain between flushings. If possible, transplant the violet to a clean pot, then soak and scrub the salt-encrusted pot to remove the salts before re-use. Plastic, glass, and glazed pots don''t accumulate salts on the rim. If the violets are bottom-watered, leach them occasionally with tepid water to wash salts from the soil.
Powdery mildew on African violet is caused by a fungus (Oidium species). The powdery patches consist of fungal strands and spores. Air currents carry the spores to healthy leaves and flowers of the same plant and to other African violets. The fungus robs the plant of its nutrients, causing yellowing or browning of the tissues. Dim light, warm days, and cool nights encourage the growth of powdery mildew.
Apply a fungicide labeled for this disease, following label directions. Remove infected flowers and flower buds and badly infected leaves. Keep plants in bright, indirect light away from cold drafts.
This plant disease is caused by a soil-dwelling fungus (Phytophthora parasitica) that attacks the roots of African violets. The disease spreads rapidly through the root system and crown of the plant into the leaves, eventually killing the plant. The fungus is active over a wide range of soil moisture conditions. It may be spread by contaminated soil or pots or carried from one pot to another on the fingers when the soil is tested for moisture. It may also be spread from pot to pot if pans are used to subirrigate plants.
Discard severely affected plants and the soil in which they grew. Wash and disinfect the pots before reuse. After handling infected plants, wash your hands thoroughly before touching healthy plants.
Members of the African violet family are very sensitive to rapid temperature changes. Water spots occur most commonly when cold water is splashed on the leaves while the plant is being watered. If this happens in light, chlorophyll is destroyed. In this plant family, all of the chlorophyll in the leaves is found in a single layer of cells near the upper surface. If the chlorophyll in that layer is broken down, the green color disappears, and the color of the underlying leaf tissue is exposed.
Irrigate with water at room temperature, which will not cause spotting if it touches the leaves. Spotted leaves will not recover. Pick them off if they are unsightly. Water sensitive plants from the bottom to avoid the danger of water spots. Set them in a pan of water that is almost as deep as the soil surface in the pot. Allow them to soak for 15 minutes to 1 hour, then drain them before returning them to their saucers.