Calag Archive

Photochemical air pollution (smog) is harmful to California agriculture, as has been widely recognized since the 1940s, when growers in the Los Angeles Basin reported silvering, bronzing, and other discolorations on leafy crops such as lettuce, spinach, and Swiss chard. Severe smog injury on these crops rendered the produce unmarketable or greatly reduced its value.

Clearing rangeland of dense brush thickets or stands of oak trees produces obvious benefits on the better soils: more and better feed for domestic and wild animals; improved water yield in the watershed; and reduced fire hazard. But there are also costs, which need to be weighed against potential returns before the decision is made to improve the land.

Spray applications of growth inhibitors to the foliage of ornamental plants have been known for many years to be effective. Sprays have been used to some extent, but possible hazards from spray drift to nontarget ornamental plants have led to the development of trunk banding and injection application techniques. However, foliar sprays, when safely used, are still the least expensive means of chemical growth reduction.

Field bindweed, or wild morning glory, probably originated in western Asia or the Mediterranean region and was accidentally transported along with agricultural crops wherever people migrated. It is now considered the world's 12th most important weed.

Biological control is seldom attempted against weeds on cultivated lands, because herbicides generally provide economical, efficient control, and farming practices may interfere with the biological agents. Field bindweed, however, reproduces from seeds that may remain alive in the soil for more than 40 years and from an extensive perennial root system. Control by cultivation or chemicals is difficult, at best. A search for biological control agents therefore seemed warranted. Even if such agents were effective only on field bindweed growing along roadsides and in other uncultivated areas, they would reduce the weed's potential for further invasion of cultivated land. A cooperative U.S. Department of Agriculture and University of California project was begun in 1970 to find biological agents for control of field bindweed.

The navel orangeworm overwinters primarily in the larval stage in mummy almonds that remain in the trees or on the ground after harvest. In the spring, moths emerge and lay eggs on the mummy nuts in the trees, and these nuts provide the principal food source of the first-generation larvae. Moths of this generation emerge to infest the current year's almond crop during the hullsplit period. Infestations may reach as high as 30 to 50 percent.

Landscape plants are often needed for difficult sites. To find plants that would grow in saline, frequently flooded soils, we evaluated 106 species on a nonirri-gated floodplain underlain with salt water along the Napa River in northern California. The site was one of many established throughout the state for landscape tree evaluation.

Before Europeans arrived, the native Americans burned chaparral brush-lands to drive out wildlife in hunting, and to increase accessibility to the land. Now chaparral is often converted to grassland to help control wildfire, increase feed for livestock and wildlife, and increase water yield, as well as to improve accessibility. Reduced sheet erosion is often another benefit.