Alice Cortese, Washington: I recently discovered small black bugs in my humidi-tray and on the bottom of pots. I threw out the gravel and used a 50 percent solution of malathion to clean the tray and bottom of pots. In a few days I noticed bugs were still on the pots. I mixed another solution of malathion and poured it on the plants. After a few minutes two of my plants wilted.

Did the plants wilt becuase the malathion solution was too strong? Did I do the right thing to get rid of the bugs?

A. First, an accurate identification of the insect is important in order for correct treatment to be given.

Second, washing with soapy water and a soft brush or cloth may be all that is needed to remove pests on houseplants. Use two teaspoons of a mild detergent to a gallon of water. Rinse plants with clear water.

Third, malathion is generally applied as a spray or dip rather than as a soil drench.

Pushbutton sprays for plants contain small quantities of rotenone, pyrethrins or other killing agents. They may be used to kill pests that can be hit readily with the spray. Read and follow all directions and precautions given on the label of the pesticide used. Several applications at weekly intervals may be required to control successive hatch-outs of pests. Malathion sprays should be used outdoors.

You can clean your humidi-tray and pebbles with soapy water or with a diluted solution of household bleach. Rinse afterwards.

The wilting of your plants was proabaly caused by lack of roots, the result of over-watering or standing in water at some earlier point in their culture.

Indoor gardening questions may be sent to Jane Steffey, The Weekly, The Washington Post, 1150 15th St. NW, Washington D.C. 30071. Please include your address and telephone number.