Q. When I brought my houseplants in last fall, they had accumulated insect pests from spending the summer outdoors. How can I prevent that this year?

Q. When I brought my houseplants in last fall, they had accumulated insect pests from spending the summer outdoors. How can I prevent that this year?

A. One of the only downsides to a summer vacation outdoors for your houseplants is the insects that can hitch a ride indoors. The best line of defense is prevention. Don't neglect your plants during their time outdoors, and deal promptly with any major insect and mite problems that appear.

When the time comes to bring them inside, plan ahead.

Instead of working frantically the first night that frost is forecast, spray them before then with a 1 percent solution of horticultural oil. Bring them indoors when the spray has dried. Spray the plants thoroughly, and concentrate on the underside of the leaves.

Some insects may still find their way indoors. Pillbugs and millipedes always come indoors with plants. They are not a major threat to the plants, and they seldom appear in sufficient numbers to cause any concern.