Master Gardener: Houseplant patrol

Healthy plants have fewer pest problems. Prevent, or at least minimize, pest issues on indoor plants by choosing the right plants and providing good overall plant care. Learn about basic care and growing needs for your plant. Select plants with growing requirements that match the indoor environment (humidity, light, temperature). Plants cannot fight off pests when they are struggling to grow in too little light, overly wet or dry soils, too hot or too cold air temperature, etc.

Water plants properly. Know how much water your plant needs. Water the soil at the base of the plant, not the leaves. Be sure the plant’s pot drains well. Avoid letting plants stand in water. Over-watering and poor drainage can cause root rot and encourage fungus gnats as well as other pest issues.

Understand your plant’s nutritional needs. Apply fertilizer at half the recommended strength. Fertilize when the plant is actively growing. Keep the plants clean. Keep soil surface free of dead leaves, stems and flowers. Wash plant leaves with a damp cloth as dust and grime can reduce plant health. Never use leaf shine products or milk. Prune out dead branches and stems.

Use new, sterile potting soil when potting plants. Never pot indoor plants using soil from the garden. Avoid using soil from open bags of potting soil that have sat outside for potting indoor plants. Save it for your outside pots. Plant in clean pots and wash soil off of plant roots.

Early detection is key to managing pests. Finding pests before they become a problem is the best way to keep insects at bay. Thoroughly examine all plant parts and containers before bringing them home from the store or indoors for the winter. Inspect tops and undersides of leaves for insects, webbing, holes and eggs. A magnifying glass may be helpful. Watch for honeydew, a shiny sticky substance made by aphids, mealybugs and scale insects found on the upper surface of leaves as well as on table tops and other items around and under the plant. Check plant containers for signs of pests along edges, rims, the bottom of pots, saucers, crevices. Remove if found. Isolate newly acquired plants for one to two weeks to allow any possible pest problem to become visible. Check for pests when you water, fertilize or clean plants. Some pests like springtails and fungus gnats will move due to the water, making it easier to detect them. Use yellow or blue sticky traps to detect flying insects like whiteflies, fungus gnats, winged aphids or thrips.

Many insect problems on indoor plants can be managed using nonchemical methods. Leaves can be washed by wiping leaves with a damp paper towel, changing towels often to prevent spread, or spray small plants in a sink or large plants in a shower. Physically removing pests by handpicking earwigs, caterpillars, slugs and millipedes is successful. Small numbers of scale insects can be removed using a fingernail file or something similar. Mealybugs can be removed using tweezers or a cotton swab dipped in alcohol. Some pests can be removed using a forceful spray of water. Repot with new potting soil to eliminate soil-borne pests. Use clean pots and wash soil off plant roots.

Pruning the plant may work if the pest issue is isolated to a few leaves, stems or branches, but it may be necessary to discard the plant if it is heavily infested. If you need to use pesticides for pest management, be sure to follow label directions of the product.

Information from Jeff Hahn, Extension Entomologist and Julie Weisenhorn, Extension Educator 2018.