Q: Year in and year out,...

Q: Year in and year out, the most ubiquitous garden pests I have had to contend with have been whiteflies, which suck the juices from both ornamentals and vegetables. What can be done? --R.C., Anaheim A: You can control whiteflies on many fruit and vegetable crops by using either diazinon or malathion. Be sure, however, that the plants you want to treat are specifically listed on the product label. Use the insecticide orthene on ornamentals, such as hibiscus and fuchsias. In all cases, it is important to spray the undersides of the leaves. Repeat treatments, at five- to seven-day intervals, are usually required. It is also helpful to place the yellow-green sticky cards (available at nurseries) that work like flypaper in the vicinity.

Q: Can soil drainage be improved with the synthetic soil conditioners now on the market, or can I get better results with compost?--G.W., Los Angeles A: Synthetic polymer soil conditioners have the advantage over compost in that only a few pounds are needed, rather than hundreds of pounds of compost. Their use improves soil drainage, lessens soil erosion, eliminates crusting on the soil surface and reduces the stickiness of clay soils. Also, these conditioners last for years.