Indoor or tropical plants are valued for their ability to clean the air as well as add the allure of a tropical location, especially at this time of year when the temperature outside can be frigid. Air inside a typical Central Alberta building is dry in winter, even with a humidifier. Temperatures within the average building range from 15 to 22 ˚ C depending on settings and time of day. This contrasts to the average humid, tropical temperature of 18 ˚ C plus. The typical no-tropical indoor climate stresses tropical plants making them more prone to insect infestations.
When a plant begins to look unhealthy, remove it from the general population and examine it carefully.
Spider mites, aphids, mealybugs, and soil gnats are commonly found in indoor plants. Insects can come in on other plants, clothing or hatch from eggs that have been dormant and waiting for the perfect conditions.
Spider mites are tiny insects that are hard to see without a magnifying glass. They frequent the bottom of leaves and can easily be mistaken for small imperfections or specks of potting soil. If given a nudge, they may move but often they will stay still. These pests feed by piercing the leaf and sucking out the plant’s juices.
As a colony of spider mites expands they are easier to spot. Webs will appear on the bottom of leaves and between leaves and branches. Leaves that have hosted insect often turn yellow and fall off. They may also just shrivel up.
When the infestation covers most of the plant, discard it by removing it from the house. Another alternative is to prune out all infested plant material, placing it in the garbage for a quick disposal. Spray the remaining leaves and stems with a solution of water and liquid soap. This must be repeated as an adult spider mite can lay eggs every five days.
Mature Aphids are larger insects but still under a quarter of an inch (6.5mm) in length. The pear shaped insects are found on stems and the underside of leaves. They too suck out the plants juices. Don’t be surprised if the aphids are any of the following colors: green, white, yellow, brown, yellow or black. If the aphid population becomes too large for the plant to support, the next generation to hatch will develop wings and look for a new food source. Given the correct conditions, an aphids can go from being hatched to hatching in a week.
Plants that are hosting aphids typically have misshapen or curling leaves that may turn yellow and fall off. Aphids secrete a noticeable, sticky substance called honeydew which will appear on anything below the insect.
As with the spider mites, remove any infected plant material. Spraying the remaining plant with a strong blast of water will dislodge a large number of the remaining insects and follow up with a water and soap solution.
Mealy bugs are white, fuzzy and sticky to the touch. They can be anywhere on the plant but are usually found in masses where branches connect. Colonies do not expand rapidly which means the insects are often detected before plant damage is noticeable.
Insects are usually easily removed with Q-tips dipped in rubbing alcohol.
Soil gnats, tiny black flies, do not hurt the plants but can be very annoying. They thrive in soil that is wet or moist. Letting the soil dry out between watering is the best defence. Sticky yellow paper strips can be used to capture the insects.
It takes time and patience to eliminate all insects from plant material. Before taking up the fight take cost, time involved, attachment and ease of replacement into account.
Linda Tomlinson is a horticulturalist that lives near Rocky Mountain House. She can be reached at firstname.lastname@example.org