Now that winter is here, scale insects have started showing up on my potted citrus tree and some orchids. How many other plant pests lurk, ready for a population explosion when conditions become ripe, typically in late winter?

Dowsing plants — especially indoor houseplants — with pesticides is bothersome and hazardous. Repeat applications usually are needed to catch each wave of the emerging pest population at its most susceptible stage.

A systemic pesticide such as Bonide Systemic Insecticide Granules, which spreads within the plant, also has shortcomings. It creates a toxic plant, which can poison any pet or child who nibbles a leaf.

Indoors, where rain and wind can’t carry away residues, you have to be wary even of pesticides labeled “natural.” Natural does not mean nontoxic. Rotenone, for example, is an all-natural pesticide extracted from a tropical plant, yet it is much more toxic than, say, malathion, a synthetic pesticide.

I try to avoid using pesticides altogether. They are just one approach to controlling pests, and should be the last one.

For now, I’m dealing with scale insects by flicking any that I see off leaves with my thumbnail. I know I won’t eliminate them with this brute-force method, but I can at least keep the population in check.

I’ve used similar methods against aphids, crushing them where they congregate on leaves near the tips of stems, and against mealybugs, doing them in with a cotton swab dipped in alcohol.

Keeping an aphid-infested plant in the shower will wash the pests away and create conditions inimical to another common pest, red spider mites, which are hard to see but make their presence known by imparting a bronze cast to leaves.

Trapping is a more elegant approach to pest control. Thwart aphids on single- or few-stemmed plants by blocking travel of the ants that herd and protect them: Wrap a sticky band around the stem or stems. Masking tape coated with sticky Tangle-Trap works and lasts for weeks. If clouds of whiteflies puff up whenever you brush against your geraniums, place yellow cards coated with oil or Tangle-Trap near the plants.