Q. Is there such a thing as a broad leaf weed killer that I can use on my lawn? Can they be used near trees?

P.M., Hollywood

If herbicides are needed, try to carefully use a spot treatment with a systemic herbicide such as those containing the active ingredient glyphosate. This kills the whole plant, including the roots. Several applications may be needed for perennial weeds.

Herbicide use should be the last choice in weed control. Also, “weed and feed” products have been found to damage shrubs and shade trees when improperly used. The herbicide atrazine has been found to pollute ground water.

To avoid weed problems, use these methods first: encourage turf growth by proper maintenance practices (fertilizer, watering, mowing, pest control). All too often, lawns are cut too short and watered too often. This stresses the grass and allows weeds to become established. Water only when needed (when the majority of grass blades fold in half) and set the mower to the highest setting so that the lawn is three to four inches tall after mowing.

If you have to use herbicides or remove a lot of weeds by hand, an empty spot in the lawn is a great place for the next weed to come up. Quickly fill in any empty spots by cutting a piece of healthy lawn and plant those pieces in the bare area.

Hand pull weeds before they become out of control and before they bloom. Mow the weeds before they produce seeds.

If the area is too shady for grass, grow plants that are shade-tolerant. Here’s a web site showing low-maintenance plants for South Florida: http://miami-dade.ifas.ufl.edu/fyn-publications/index.shtml.

Insect Samples

Send undamaged (live or dead) insects in a crush-proof container such as a pill bottle or film canister with the top taped on. Mail them in a padded envelope or box with a brief note explaining where you found the insects.

Do not tape insects to paper or place them loose in envelopes. Insect fragments or crushed insect samples are almost impossible to identify.

Send them to the address of your county extension office, found in the blue pages in the phone book under county government.

Adrian Hunsberger is an entomologist/horticulturist with the UF/IFAS Miami-Dade Extension office. Write to Plant Clinic, 18710 SW 288th St., Homestead, FL 33030; e-mail dade@ifas.ufl.edu.