Great Plains Gardening
March 14, 2003
As promised, this week I will deal with houseplant problems and possible causes, plus some comments on keeping the plant healthy. These suggestions come from the IPM Series: Houseplants from Maryland Cooperative Extension.
If your plants are wilting there could be several causes: over watering, lack of water, root rots or stem cankers. "Over watering can cause root rot. Healthy roots should be light colored and firm. To control such a situation use a well drained, peat based potting media. Severely damaged plants should be discarded." Is it root rots? "Pull plant out of the pot and observe roots for discoloration. Diseased roots will appear dark and soft. Remove diseased plants from their pots, cut out infested portions (rotted), and replant remaining healthy sections. Take cuttings and root them in sterile potting mix." Stem cankers are discolored areas on the stem. Simply prune out the affected areas.
If you find leaf yellowing, foliage fades, yellows brown or wilts there are three things that could be the problem—insects, high soluble salts and the above mentioned root rots. The high soluble salts can be leached. "Leach the soil at least three times with pot volume of fresh water." The insects could include aphids, spider mites, mealy bugs, or white flies. "Aphids are small soft-bodied insects found on leaves, stems and flower buds. Spider mites are minute pests that feed on lower leaf surfaces, webbing may be visible. Mealy bugs are white cottony insects. Whitefly adults are tiny white insects that fly from the plants when disturbed. The immature stages are found on lower leaf surfaces. Regularly rinse plants with water to keep down pest problems. Use a registered houseplant spray to control pests. Plants damaged by heavy insect or mite feeding can be injured by insecticidal sprays. Severely damaged plants should be discarded. Remove diseased plants from their pots, cutout portions (rotten), and replant remaining healthy sections. Take cuttings and root them in sterile potting mix.
"Bleached or whitened leaves could possibly be caused by excessive light or sunburn. To control, acclimate plants slowly to higher light intensities."
"Leaf spots and leaf blotches can be caused by water spots, sunburn, various fungi, or bacteria. Remove spotted leaves and impro9ve air circulation for leaf diseases."
"Cold injury can cause leaf or shoot blackening and symptoms may continue for up to a week after exposure. Protect plants from temperatures below 55 degrees"
"Leaf scorch can be caused by abiotic stresses such as over fertilization, high soluble salts, or lack of water. Scorching symptoms can occur along leaf margins or between veins. Leach excessive fertilizer from potting mix by flushing with water or repot with fresh potting media."
"Stunted, twisted and distorted plant growth can be caused by aphids, cyclamen mites or viruses. Cyclamen mites are predominately a pest of flowering plants. New growth is affected first. With viruses, the foliage appears mottled green and yellow, and the plants can be stunted. Aphids can be controlled with a stream of water or with a registered insecticide. Cyclamen mite infested plants and virus infected plants cannot be cured and should be discarded."
"White powdery coating on leaves is a sign of powdery mildew fungi that grows on the leaf surface. For control, provide better air circulation and pick off infected leaves. Spray with a registered fungicide if disease is severe. Check horticultural oil labels for powdery mildew control listings."
"A fuzzy, gray growth on leaves or flowers is caused by gray mold which frequently infects old faded flowers or older, lower foliage. Provide better air circulation. Pick off infected flowers or leaves. Remove old blooms or foliage."
"Fluffy white wax on the plant indicates mealy bug infestation. These can be on foliage, in leaf axles, leaf sheaths, roots and bud scales. As mentioned before, a registered houseplant spray can be used to control them"
"Few or no flowers or spindly growth can be caused by low light levels, excessive fertilizer, or cyclamen mites. Cyclamen mite infested plants should be discarded. Increase light levels by relocating plants closer to a light source or add additional artificial light sources. Reduce fertilizer applications during winter. Irrigate from the top of the pot to leach out excess fertilizer salts."
Do you notice any flying insects around your plants? They could be whiteflies or fungus gnats. Fungus gnats are tiny black flies flying near plants or near light sources. For control allow potting media to dry between waterings. Beneficial nematodes may be added to the potting media to control the fungus gnat larvae. Use a registered insecticide for white flies.
If you have given your houseplants a "vacation" by relocating them outside during the summer months be sure to check them for pests, such as caterpillars, leaf feeding beetles, weevils, grasshoppers, crickets, slugs, earwigs, etc. before bringing them back into the house for the winter. It is best to repot plants with fresh potting media BEFORE bringing them back into the house to keep unwanted pests from becoming a problem.
I hope this information has been of use to you. The Extension Office has a pamphlet called Planttalk Colorado that I’m sure would be of interest. The pamphlet has a listing of over 400 gardening topics that can be accessed 24 hours a day. Planttalk Colorado is a free service that provides reliable information on a variety of horticulture topics. By calling l-888-666-3063, toll free; you will be in touch with recorded information on many subjects. Computer can also access Planttalk. Enter www.planttalk.org. Click on one of 14 categories. Click on desired topic to access text. Click on links provided to find additional information. Fill out evaluation form. Enjoy! Get educated!
Until next time…