San Joaquin Valley Has Its Own Fall Color Display

While not producing the world-renowned color display of the Northeastern United States, trees in the San Joaquin Valley can offer up vibrant yellows, oranges, even reds and purples as days become shorter and weather cools. Liquidambar and Chinese pistache are among the most colorful shade trees in the fall. Willow, birch and poplar contribute yellows. Perhaps the most colorful of natural landscape shrubs is poison oak, according to John Karlik, Kern County UC Cooperative Extension environmental horticulture farm advisor. In the fall, chlorophyll in the leaves breaks down and orange and yellow pigments which have been present all along become visible. The best weather for glorious autumn color, Karlik said, is sunny and dry with cool but not freezing temperatures. Under these conditions, plants synthesize new pigments, each with a particular color, which may be crimson, scarlet, blue-violet, red, purple or mauve. For more information contact John Karlik at (805) 868-6220, jkarlik@ucla.edu.

Looking at the Big Picture for Whitefly Control

Farmers have long known insects ignore farm boundaries, but controlling them is still almost always done on a farm-by-farm basis. Kern County UC Cooperative Extension farm advisor James Brazzle believes the destructive silverleaf whitefly is demanding a new approach. For two years, Brazzle has teamed up with a diverse group of scientists, farmers and industry representatives to try waging a regional battle against a pest capable of devastating economic damage. "Whiteflies are overwintering in citrus, then moving to certain weeds, melons and vegetables, and later to cotton," Brazzle said. Damage in cotton is minimized when sunflower, thistle, ground cherry and morning glory weeds are controlled, melons are harvested early and the residue is quickly, and repeatedly, plowed under. Then meticulous care is taken to mature the cotton crop early, making it less attractive to silverleaf whiteflies looking for luscious green leaves in late August. With over 10,000 acres of Kern County farmland understudy, Brazzle has found that reducing early-season hosts can keep late-summer populations at manageable levels. For more information contact James Brazzle at (805) 868-6215, jrbrazzle@ucdavis.edu.

Nitrate Pollution Potential of Sewage Sludge in Agriculture Measured for First Time in Kern County

The use of human and animal wastes to fertilize crops is as old as cultivated agriculture. But the large-scale application of sewage sludge on farmland still raises questions. One issue surrounding biosolids is the conversion of organic forms of nitrogen into inorganic forms. Inorganic, or mineralized, nitrogen is the preferred form for plants but, because it moves freely with water, raises the potential for groundwater pollution. "Mineralization rate study results on biosolids have ranged from 10 percent or less to as high as 85 percent the first year after application," said Blake Sanden, Kern County UC Cooperative Extension farm advisor. "The Kern County industry currently uses a 20% assumption, but we don't have any in-field nitrate mineralization data for our area. That's what we're trying to generate." Sanden is now starting the study on two 300-acre fields in western Kern County. For more information contact Blake Sanden at (805) 868-6218, blsanden@ucdavis.edu.

Jeannette Warnert
Public Information Representative
Ag and Natural Resources
UC Center
550 E. Shaw Avenue
Fresno, CA 93710