The number of pesticides that may be used on house plants indoors is limited, so thorough clean-up is important for satisfactory pest control.
Every few weeks, carefully examine leaves, pots, and roots to determine which action may be necessary. Check first for common house plant pests. Among these are spider mites, mealy bugs, and scale.
Outdoor pests, such as aphids and grasshoppers, may be carried indoors unless eliminated during the plant clean-up. Some pests may hide in the pots which should also be checked and eliminated before plants are moved inside.
Mealy bugs and scale are two pests that attach themselves to the leaves and stems of many plants and suck out plant sap. Mealy bugs are covered with a cottony mass, while scales are covered with a brown waxy material.
Because they are so well protected these pests are difficult to kill with pesticides available for house plant use. Addition of detergents to the pesticide solution helps it penetrate the covering, particularly for control of mealybugs.
Household detergents at a rate of about ½ teaspoon per gallon of water added to a malathion dip or spray can make the treatment more effective. For either pest, it will be helpful to remove many of the visible insects before spraying. The eggs of these insects are laid under the protective coverings.
Pesticides normally use for control of the scale and mealy bugs do not kill the eggs, so several spray treatments at four to five-day intervals may be necessary to totally clean a plant. Some of these pests may also live on the roots and therefore a soil treatment as well as a spray or dip is also beneficial.
Spider mites are minute pests usually not noticed until becoming very abundant. Damage can appear as yellowish blotching on the leaves which progressively gets more severe. Fine webbing can appear on the undersides of the leaves or between the leaf base and the stem. Often the webbing will become more apparent when plants are misted with a fine atomizer. If spider mites are suspected, first wash the leaves and stems with a strong stream of water. Direct the spray upward to especially wash underside of the leaves.
After thorough cleaning, an insecticide, such as malathion, might be used to help kill mite eggs so several applications at four to five-days intervals are necessary for complete clean up. Detergents added to the water will also help to make the materials flow into small spaces where pests may hide.
Pot and soil inspection is also important at the time plants are moved indoors. Sow bugs (pill bugs), millipedes, earthworms, slugs, or crickets may have found refuge there. Many may hide in the base of the pot inside the drainage hole or holes.
If plants are small enough, turn them over and knock the root ball out of the pot. This will usually expose these pests and make their removal easy. Large plants may have to be turned on their sides and a stick or other implement used to probe into openings to try to expose hidden pests.