California Agriculture

The years 2003 and 2005 were pivotal for the North American cattle industry. In May 2003, Canada announced its first case of bovine spongiform encephalopathy (BSE), also known as mad cow disease. This was the first time North America’s indigenous cattle had been confirmed to have BSE. Seven months later in December, the U.S. Department of Agriculture (USDA) announced that a dairy cow in Washington state (born in Canada and brought into the United States in 2001, at about 4 years old) had also tested positive for BSE. Then, in June 2005 USDA confirmed another U.S. case, this time “home-grown,” a 12-year-old cow from a herd in Texas. These events have resulted in vigorous debates over testing cattle for BSE in the United States, and several important new USDA regulations. The results of the United State’s expanded cattle-testing program will be watched closely in light of differing risk assessments about the prevalence of BSE in the United States. Increased testing could also have serious impacts on both domestic consumption and export markets for U.S. beef. Even as USDA continues to implement and refine new testing and other regulations, challenges from other countries and watchdog groups may result in more rigorous and transparent testing procedures. Other groups, including the beef industry, oppose more rigorous testing as causing unnecessary alarm.

Preventing the spread of mad cow disease through contaminated cattle feed is a major concern of beef and dairy producers, regulators and consumers around the world. Routine testing of cattle feeds for the presence of banned substances is a critical control point in assuring animal health and food safety. We compared the results of two test procedures (a real-time polymerase chain reaction [PCR] assay and a commercially available ruminant antibody detection kit) on five cattle rations spiked with bovine meat-and-bone meal, or with bovine dried blood. The real-time PCR consistently detected these contaminants at lower levels in each of these diverse cattle rations.

Livestock grazing remains a common practice on California’s hardwood rangelands. This can create problems for oak regeneration because grazing has been identified as one of the factors limiting the establishment of certain oak species. Previous research, as well as recent studies at the UC Sierra Foothill Research and Extension Center, suggests that cattle will damage both planted and/or naturally occurring oaks, but damage varies by season with less during the winter when deciduous oaks do not have leaves. Damage is also influenced by the density and distribution of cattle stocking. Oaks taller than 6.5 feet seem relatively resistant to cattle damage in lightly to moderately grazed pastures, but smaller seedlings need protection.

The glassy-winged sharpshooter (GWSS) is an introduced pest that spreads the bacterium Xylella fastidiosa, which causes a variety of diseases such as Pierce’s disease in grapevines and leaf scorch in oleanders. GWSS has been established in Southern California since about 1990 and has also successfully invaded French Polynesia, Hawaii and Easter Island. Researchers from UC, the U.S. Department of Agriculture and the California Department of Food and Agriculture have introduced parasitic wasps for the biological control of GWSS. Four parasitoids from the southeastern United States have been released and appear to be establishing in Southern California. Parasitoids from Argentina are also being evaluated in quarantine but have not yet been released.

The red gum lerp psyllid is an insect native to Australia, where it feeds upon eucalyptus species. Since 1998 this psyllid has spread throughout California, resulting in millions of dollars in damage and control costs. To help suppress the red gum lerp psyllid, a biological control program was initiated and a psyllid-specific parasitic wasp was imported from Australia in 1999 and released in 2000. In most coastal regions this biological control agent has provided substantial control, but in some interior regions the psyllid still remains a problem. Researchers are continuing their investigations to determine if full statewide suppression will be realized eventually, or if further importation of new parasitoid species is needed.

The Healthy Schools Act of 2000 established right-to-know procedures for pesticide use in California public schools, and mandated using least-toxic pest management methods as state policy. In a survey conducted 2 years after the law’s passage, school districts that had integrated pest management (IPM) programs generally used more ecologically sound pest management tactics than districts that did not, and most of those said that IPM had improved their pest management effectiveness. The Healthy Schools Act requires that schools post warning signs, keep pest management records, provide notifications to parents and staff, and maintain a list of parents desiring further notifications. A majority of California’s school districts have implemented at least three of these four requirements, with about half reporting full compliance.

A comprehensive survey of full-time almond growers in the three primary almond-producing regions of California showed that growers rely substantially on pest control advisers (PCAs) for pest management decision-making. Independent PCAs communicated more frequently with growers than PCAs who are employed by agricultural product suppliers. Growers who use independent PCAs tend to feel more knowledgeable about integrated pest management (IPM) and report the use of more complex pest-monitoring techniques and control practices. The use of insecticide sprays, however, is independent of the type of PCA employed, and the percentage of growers using them has declined substantially since a 1985 survey.

While ‘Paradox’ hybrid seedlings are often the rootstocks of choice for California walnut orchards, there is a resurgence of interest in using English walnut seedlings because walnut blackline disease, which is endemic in many California walnut production districts, does not affect them. We compared the growth and productivity of walnuts on English rootstocks from a variety of sources to those on Paradox rootstock. The growth and productivity of ‘Chandler’ walnut trees were similar among trees on seedling English rootstocks in one trial, but trees on English rootstocks were smaller and had lower production than Paradox hybrid–rooted trees in the other.

Hay stored for prolonged periods of time decreases in value for feeding livestock. The irrigated Sonoran Desert of southeastern California and western Arizona is the hottest inhabited part of the United States, with summer temperatures routinely exceeding 100°F from May through October. We evaluated the effects of three methods of hay storage there during the summer: uncovered, under a roof and under a tarp. After 21 weeks, hay that was protected from summer solar radiation, either by the use of barn storage or plastic tarps, had more digestible content.