For the past few years, we have been bothered by flies that go around and around in circles in our covered entryway. We have sprayed and sprayed, using the strength strong enough to kill mosquitoes, and still they are here. What causes this, and what can we do to encourage them to do this dance someplace else?
– Jackie, Citrus Heights
Most measures to control houseflies are nonchemical, says UC master gardener Bill Pierce. Selective use of insecticides against houseflies is one component of a total fly-management program and should be used only after all nonchemical strategies have been employed.
While humans are most commonly bothered by the adult stage, the larval stage should be the prime target for control. Elimination of larval habitat is the preferred method of fly suppression. By removing the material in which larvae develop, the life cycle of the fly can be broken, preventing subsequent production of the adult pests.
While chemical pesticides may be necessary for suppressing adult fly populations in some situations, they are not a substitute for prevention through elimination of breeding sites. Flies can develop a resistance to insecticides in a few generations, so use insecticides only as a last resort to obtain immediate control.
Outdoors, apply residual insecticides to surfaces such as walls and ceilings that are being used by the flies as resting areas. Fly baits used in trash areas are effective in reducing the number of flies around buildings if good sanitation practices are followed.
For more information on identifying types of flies and appropriate control, send a self-addressed, stamped, 42-cent, business-size envelope to PN 7457, UC Cooperative Extension, 4145 Branch Center Road, Sacramento, CA 95827. This information also is available online at www.ipm.ucdavis.edu.
I want to put in a shade tree in the middle of my patio. When we poured the concrete, we left a 6-foot circle in which to plant a tree. After we dug the hole for the tree, it rained and the hole filled with water but didn't drain. It looks like we have clay soil. It is possible to put a shade tree here? Which one would survive?
– Theresa in Roseville
Your soil probably has an underlying layer of hardpan that limits its ability to drain. The problem may have been complicated in digging the hole; the sides of the hole may have become glazed. Neither water nor tree roots will easily penetrate the soil.
If you haven't yet filled the hole, remove the glaze by shaving one inch of the soil off the sides before you plant. Drilling through the hardpan can improve drainage. An alternative is to provide additional root space by installing a raised planter in the 6-foot circle. You'll probably want to choose a tree that is shallow rooted to compensate for your lack of drainage.
For a list of trees as well as a chart for quick reference to a few of the more common trees found growing in and around Sacramento, send a self-addressed, stamped, 59-cent business-sized envelope to EHN No. 1, UC Cooperative Extension, 4145 Branch Center Road, Sacramento, CA 95827. The Sacramento Tree Foundation Web site is also an excellent resource at www.sactree.org.
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