Calag Archive

Eucalyptus trees have been important components of the California urban landscape for almost 150 years. Until 1984, they were free of both insect and disease pests. In the last 16 years, however, a series of herbivorous insect species have been introduced into the state, probably accidentally, causing significant damage to the trees. Research programs have provided solutions to some of these pest problems, but more pests are continually introduced, recently the red gum lerp psyllid, the lemon gum lerp psyllid, and the eucalyptus tortoise beetle. Scientists are developing new strategies to control the recent invaders in concert with existing pest management programs, integrating methods across broad geographic, horticultural and economic scales.

Growers and pesticide applicators in California are legally required to file pesticide use reports with details about every application to commercial crops. We used the individual applicator records to document a decline in the use of organophosphate pesticides (OP) on almond and stone fruit orchards during the rainy season in California, a time period in which the trees are dormant. The decline is important because dormant applications are a major source of surface water contamination and the Federal Clean Water Act mandates a reduction in movement of OPs into surface water. However, the decline in use of OPs has been accompanied by an increase in use of pyrethroid pesticides, particularly in stone fruit orchards. Additional implementation of “reduced-risk” integrated pest management practices could further reduce use of dormant applications of OPs and pyrethroids on almonds and stone fruit orchards.

Mass releases of commercially produced Trichogramma wasps can be used to reduce damage from codling moth by 60% in walnut and pome fruit orchards in California. Results from field trials indicate that release rate and evenness of distribution are important factors influencing the effectiveness of wasp releases, and that damage reduction is more effective in walnuts and pears than in apples. Because the environmental risks of large-scale releases of Trichogramma wasps are likely to be small, wasp releases could be integrated with pheromone-based mating disruption for effective management of codling moth.

During the 1990s, the cotton aphid (Aphis gossypii Glover) escalated from an occasional pest to an annual, severe pest of San Joaquin Valley (SJV) cotton. Although the cotton aphid is not a new insect in the SJV, the change in the bionomics of this pest dictated that new research efforts be directed toward its biology, damage thresholds and management. The 1980s saw major shifts in agronomic practices. For example, the introduction of a plant growth regulator allowed growers to promote vigorous plant growth, rather than limiting growth and yield potential through the practice of water and nitrogen stress. Recent field research has shown that applying high rates of nitrogen to cotton plants increases cotton aphid reproductive rates and can create conditions favorable to aphid outbreaks. The new practice of promoting vigorous growth may have created an optimal host plant environment for cotton aphid reproduction and survival. In addition, the shift to using pyrethroids to control other arthropod pests has enhanced the buildup of cotton aphid populations. The severe aphid outbreak during the 1995 cotton growing season served as a focal point to bring the industry together to discuss the status of cotton integrated pest management and to plan future directions. Results of this effort include increased awareness, greater understanding of cotton aphid biology and improved pest management decisions.

Ongoing research projects integrate chemical, mechanical, cultural and biological techniques to control yellow starthistle, a prolific weed now infesting between 10 million and 15 million acres in California. With many options available to land managers, developing a long-term, strategic management plan most suitable to a specific area can be complicated. It requires careful consideration of the advantages and disadvantages of each option and how best to incorporate appropriate ones into an effective program. Management strategies include timely mowings, grazing, clover plantings, biological control insects, prescribed burning and selective applications of herbicides. In addition to new developments in the management of yellow starthistle, public awareness of invasive weed issues has translated into major legislative changes that should encourage and assist private and public landowners and managers to initiate long-term programs to prevent and manage invasive weeds, particularly yellow starthistle.

Interplanting grasses into alfalfa effectively uses grass competition to reduce the amount of weeds in alfalfa hay. The increased production offsets a lower price for the hay content, making the alfalfa-grass hay equally profitable to alfalfa hay sprayed with herbicide. This technique avoids plant-back restrictions from use of some herbicides. Alfalfa weevil populations can be reduced below threshold levels, providing additional benefit from the technique. The percentage of growers interplanting did not change but nearly half of the 24% of growers using interplanting are new users of the technique. Cooperative Extension was viewed as the most useful source for interplanting information by 64% of farmers surveyed.

Preplant soil fumigation with methyl bromide is scheduled to be phased out by 2005. Chemical and nonchemical alternatives are being researched and identified. Soil solarization and/or biofumigation can help fill the gap in certain cases. These alternative methods of soil disinfestation are also of value to organic growers, home gardeners and others who will not or cannot use the soil fumigation chemicals employed by many conventional commercial growers.

Because of declining anadromous fisheries, resource managers are concerned about the timing and quantity of water flows in Northern California's Scott River. We analyzed 48 years of flow and precipitation data to improve our collective understanding of the Scott River fall flow regime and to provide information for current and future fisheries-restoration efforts. Fall flows are primarily controlled by the water content of snow and precipitation during the previous 12 months. These two factors account for nearly 80% of the variation in fall flows. Our analysis shows that downward trends in fall flows appear to be explained by a decrease in the water content of the snow falling on the Scott River watershed. This information will be useful in assessing the relative benefits of conservation and restoration strategies against the larger background of climate-caused changes in river flow.

Growers and pesticide applicators in California are legally required to file pesticide use reports with details about every application to commercial crops. We used the individual applicator records to document a decline in the use of organophosphate pesticides (OP) on almond and stone fruit orchards during the rainy season in California, a time period in which the trees are dormant. The decline is important because dormant applications are a major source of surface water contamination and the Federal Clean Water Act mandates a reduction in movement of OPs into surface water. However, the decline in use of OPs has been accompanied by an increase in use of pyrethroid pesticides, particularly in stone fruit orchards. Additional implementation of “reduced-risk” integrated pest management practices could further reduce use of dormant applications of OPs and pyrethroids on almonds and stone fruit orchards.

Nutrition knowledge and dietary intake among Hispanic teenage girls were assessed before and after a nutrition education intervention. We found that subjects were consuming several important nutrients at levels below current government recommendations. On average, Hispanic teenage girls consumed folate, calcium, zinc and iron at levels that were 40%, 36%, 18% and 8% below current recommendations, respectively. Participation in the five-lesson nutrition education program resulted in a 50% increase in nutrition knowledge and modest changes in dietary behavior; we observed improved dietary intake of vitamin C. Long-term interventions are needed to improve dietary habits as one means of enhancing overall health.

Tuolumne County retail merchants think that they are not capturing the lion's share of local sales, but they are! County residents do not go out of the county to shop as much as businesses think. A survey conducted in 1997 by the UC Cooperative Extension Office in Tuolumne County surveyed shoppers and checked perceptions of local business owners. The survey found that the proportion of money that is spent out of the county is not as high as businesses surmised. This follow-up to a similar study conducted in 1989 also showed that businesses are capturing more local dollars than they were 8 years earlier.

Grading is important to ensure the production of high-quality foods, but it is usually done with error, distorting market signals and diminishing incentives to produce high-quality products. Size is the main quality criterion for dried prunes and the crucial characteristic in determining prune value. We studied the economic effects of errors in commodity grading, focusing in particular on the implications of one-way (asymmetric) grading errors, namely when small, low-quality product is erroneously classified as high quality, but not vice versa. In an application to the California prune industry, we estimated the extent to which large prunes are undervalued and small prunes are overvalued. We conclude that grading error means that prunes graded as high-quality may not really be high-quality prunes. The presence of these incorrectly graded prunes depresses the prices that growers are paid for high-quality prunes and increases the net returns for small prunes. As a result, growers face reduced incentives to produce larger prunes.