We are becoming interested in organic methods for growing plants. The fertilizers are not hard to find, but we're having a difficult time locating biological controls for pests. Do you know where we could find a listing of controls and suppliers?
Your request is among many that we've received, and our thanks go to two publishers of this information.
You can write to: California Department of Food and Agriculture, Biological Control Services Program, 3288 Meadowview Road, Sacramento, Calif. 95832, as well as Resources for Organic Pest Control 1982, Readers' Service, Organic Gardening, 33 East Minor Street, Emmaus, Pa. 18040.
The first addressee lists suppliers of predators, parasites, and diseases that attack insect pests; the second addressee lists suppliers of insect traps, mechanical barriers, and the like, in addition to the predators and parasites of insect pests.
We're sure these folks would appreciate a self-addressed, stamped envelope along with your request.
A friend offered us some sawdust last summer, and we used it as a mulch between the rows of our vegetables. A short time later the plants appeared stunted and turned yellow. Was the sawdust at fault?
When fresh sawdust (or other ''raw'' organic matter) is added to soil, fungi and bacteria pounce on it to break it down. They consume so much nitrogen in the decomposition process that plants are temporarily robbed of this necessary element, which produces green growth in plants.
This shortage may be offset by adding a gallon of liquid plant food (mixed according to directions for regular feeding) per bushel of sawdust.
What are some of the orchids we can grow in our home without a lot of fuss and bother? What are the main requirements?
A surprising number of similar questions came to us after Peter Tonge's recent mention of the Eleventh World Orchid Conference, scheduled for March 5-12 , 1984, in Miami, Fla. It should be a spectacular and informative affair.
We have grown cattleyas and phalaenopsis (moth orchid) with less trouble than African violets. In general, night temperatures should run between 60 and 65 degrees F. Daytime temperatures from 70 to 85 degrees F. are acceptable to both. They need a special well-drained medium, which can be one part osmunda (tree fern) or fir-bark chips and one part perlite.
Cattleyas need watering about once a week (and can dry in between); phalaenopsis should not be allowed to dry out completely between waterings. Both should have regular feedings and humidity of about 50 percent.
We have supplied the required moisture by setting the pots on slats covering a 3-inch-deep pan containing about 2 inches of water. Cattleyas need good light, but should be lightly shaded from direct sun. Phalaenopsis thrives with less light, and can be grown in north windows.
If you want more information on growing orchids in the home, send a self-addressed, stamped envelope to us at The Christian Science Monitor, One Norway Street, Boston, Mass. 02115. Write ''orchid'' on the mailing envelope.
Of 30,000 species, about seven grow well in a home, and many more if you have a greenhouse.