1 week Ago By Kelly Feehan Nebraska Extension-Platte County
Insects and mites can rapidly develop into high populations on indoor plants. Many are very small and go unnoticed until a houseplant exhibits symptoms of insect feeding. Once a plant is heavily infested, control becomes challenging.
The most common houseplant pests are spider mites, white flies, mealybugs and scales. All are sap feeders who use piercing sucking mouthparts to pull sap from leaves. Unlike chewing insects whose feeding creates noticeable holes in leaves, sapsucking insects can go undetected until leaves begin to turn yellow or brown.
In the warm, dry climate of homes, insect populations increase rapidly with some insects having a new generation once a week up to once a month. Houseplant pests are also protected indoors from wind or rain to knock them off of plants and from natural enemies who keep them in check. Monitor houseplants on a regular basis for signs of insects.
For spider mites, check leaf undersides for very fine webbing between leaf veins. A hand lens may be needed. White fly adults look like tiny, white gnats flying out of plants.
The immature nymphs are white, scale-like, and found on leaf undersides. Sticky or shiny leaves are a sign of white flies, mealybugs and some scale insects. When feeding on sap, insects exude honeydew out of their bodies making plant leaves feel sticky.
Mealybugs appear as a cottony white mass on stems and leaf bases. This moist cottony mass is actually where eggs are laid. After hatching, mealybugs move about the plant.
They can move to the roots for a period of time, then return in high numbers on leaves. Scale insects look like flat brown or white scales on leaves and stems. The insect feeds on sap from beneath the protective scale covering.
Eggs hatch from beneath the scale, and nymphs crawl to new locations where they attach themselves and grow a new covering. The following practices are useful in keeping insect populations at bay. Wash plants periodically with a spray of water or gentle shower.
In the shower, place tin foil over the container and soil to keep it from washing out. Called syringing, this is most helpful for spider mites who are easy to dislodge if leaf undersides are hit by the water stream. Larger insects can be handpicked and scales can be scraped off.
For whiteflies, small, hand-held vacuums may be used on plants on a regular basis. Dabbing mealybugs masses, not plant leaves, with alcohol on a cotton swab is helpful. Be careful as alcohol can damage leaves.
Yellow sticky traps are used to reduce flying insects. Sticky traps are sold commercially or made by cutting bright yellow cardboard to an appropriate size and covering it with petroleum jelly. Attach it to a dowel stick and insert the stick into soil.
Insecticidal soaps help reduce populations. They work best on small, soft-bodied pests like aphids, mealybugs and spider mites. The limitations of insecticidal soaps are they must contact and wet the insect to work, they have no residual effects, and insecticidal soaps can harm plants if label directions are not followed.
And while liquid hand soaps and dishwashing detergents have insecticidal effects, there is greater potential for plant injury if plant owners mix their own. If a houseplant is infested with a soft bodied insect, and insecticidal soap is used, purchase one formulated for houseplants and follow label directions to avoid injuring plants. Kelly Feehan Kelly Feehan is a community environment educator for Nebraska Extension-Platte County.
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