Pre-emergence herbicides such as simazine and diuron (Karmex) are widely used for annual weed control in commercial apple and pear producing areas outside California. A 1964-65 survey of California orchards showed that very few acres of apples and only about 1000 acres of pears were sprayed for annual-weed control during that winter. Both simazine and diuron have been registered for use in apples and pears by the state of California and USDA. New developments in orchard culture, including hedge-row planting of pears, together with the scarcity of hand labor, have resulted in a recent upsurge of interest on the part of California orchardists.

Cooperation in conducting these tests was obtained from D. E. Bayer, L. L. Buschmann, D. I. Grover, H. M. Kempen, F. M. Charles, W. S. Scyman, D. E. Ramos, E. C. Koch, N. W. Ross, G. R. Post and many other farm advisors who contributed information and support to this program—as well as many California farmers. Jim Quick conducted the organic-matter and physical analyses of the soils.