Soon you will begin the task of bringing in your houseplants for winter. If after a few days, they tend to appear to look poor in health, the cause may be an unfavorable environment in your home or even disease problems. The unfriendly plant environment could be the result of lower light, humidity or temperatures, drafts or improper watering or fertilization. These adverse growing conditions often lead to various diseases indicated by leaf drop, yellow leaves, death of leaf edge and tip and spindly growth. To keep plants looking good, become familiar with each one’s optimum growing conditions including light, moisture and fertility requirements.
If plants require high light intensity, clean the windows where these plants will be put to ensure that they receive the brightest light possible. The highest intensities generally are found in south-facing windows that are not blocked by outdoor vegetation or awnings. Plants likely will need less water and fertilizer when grown indoors so reduce these accordingly.
Another cause of the sickly appearance could be that while outdoors the plants were infested with insect pests or infected with disease organisms. This initial problem may become severe when you bring the plants indoors because the disease or insect’s natural enemies are not in your home. Diseases that spread from one plant to another usually are caused by bacteria, fungi, viruses and nematodes that come into contact with plants outdoors.
Black, brown or yellow spots may indicate a bacterial or fungal leaf spot disease. To combat foliar diseases, pick off and destroy affected leaves, leave plenty of space between plants, move them to less humid area and do not wet foliage.
Viruses are moved to healthy plants by insects and on human hands. To eliminate a viral problem, discard diseased plants. Soil borne organisms cause root and stem-rot diseases, which usually occur under very wet soil conditions. Preventive measures are to avoid over watering plants and provide good drainage.
Common houseplant insect pests are aphids, mealybugs, white flies, scale spider mites and thrips. Insecticides usually are not necessary on small infestations limited to a few plants. Dip swap in rubbing alcohol to remove light aphid and mealybug infestations, or use tweezers or your fingernails to control them. Wash off mites by spraying plants with water.
Use a solution of two tablespoons of mild soap per gallon of water and a soft brush or cloth to eliminate heavy insect infestations. If you decide to use a conventional insecticide, always read and follow the manufacturer’s label instructions.
Jeremy Williams is the Harlan County extension agent for agriculture & natural resources. Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin.