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Open Access Publications from the University of California

Volume 63, Issue 3, 2009

Issue cover


Native bees are a rich natural resource in urban California gardens

Evidence is mounting that pollinators of crop and wildland plants are declining worldwide. Our research group at UC Berkeley and UC Davis conducted a 3-year survey of bee pollinators in seven cities from Northern California to Southern California. Results indicate that many types of urban residential gardens provide floral and nesting resources for the reproduction and survival of bees, especially a diversity of native bees. Habitat gardening for bees, using targeted ornamental plants, can predictably increase bee diversity and abundance, and provide clear pollination benefits.

Diaprepes root weevil, a new California pest, will raise costs for pest control and trigger quarantines

This study presents an economic analysis of cost increases for citrus, avocado and nursery producers should the Diaprepes root weevil become established in California. First identified in Southern California in 2005, Diaprepres would mainly affect orange, grapefruit, lemon and avocado crops. The primary impacts would be increased production costs for pest treatments and increased harvesting costs to conform to quarantine regulations, in particular to ship ornamental plants out of infested regions. The estimated increase in production cost to treat Diaprepes was $609 per acre on average for citrus and avocado and $525 per acre for infested nurseries. The average increase in total cost as a share of revenues was 21.61% for oranges, 11.35% for avocados, 9.80% for grapefruit and 5.62% for lemons; for nursery growers it was less than 1%.

Losses due to lenticel rot are an increasing concern for Kern County potato growers

In recent years, lenticel rot of potato tubers, caused by the bacterium Erwinia carotovora subsp. carotovora, has become an economically important postharvest disease for Kern County growers. Disease symptoms are sunken and rotted tissue surrounding tuber lenticels, which develop after harvest and packing. In the field, the bacterium also causes Erwinia early dying, characterized by wilt and progressive necrosis of leaves, eventually resulting in potato plant death. This study confirms Erwinia carotovora subsp. carotovora as the causal agent of both problems in Kern County and establishes the link between the field and postharvest diseases. Control of both diseases is difficult and relies on the integration of cultural methods, from preplant seed-piece handling to postharvest processing.

Drip irrigation provides the salinity control needed for profitable irrigation of tomatoes in the San Joaquin Valley

Despite nearly 30 years of research supporting the need for subsurface drainage-water disposal facilities, the lack of these facilities continues to plague agriculture on the San Joaquin Valley’s west side. One option for coping with the resulting soil salinity and shallow water-table problems is to convert from furrow or sprinkle irrigation to drip irrigation. Commercial field studies showed that subsurface drip systems can be highly profitable for growing processing tomatoes in the San Joaquin Valley, provided that the leaching fraction can achieve adequate salinity control in the root zone. Computer simulations of water and salt movement showed localized leaching fractions of about 25% under subsurface drip irrigation, when water applications equaled the potential crop evapotranspiration. This research suggests that subsurface drip irrigation can be successfully used in commercial fields without increasing root-zone soil salinity, potentially eliminating the need for subsurface drainage-water disposal facilities.

Model could aid emergency response planning for foot-and-mouth disease outbreaks

Infectious animal diseases are an ever-present threat to intensive livestock production. We analyzed control technology for foot-and-mouth disease (FMD) in a livestock-intensive region of the Central Valley, using a previously developed, numerical, optimal disease-control model. We found that the alternative FMD controls we studied (early detection, herd depopulation and vaccination) can be partially substituted for one another (substitutability) without substantially changing outbreak costs. This information can be used to develop effective and efficient policies to prepare for an FMD outbreak in California.

Hay harvesting services respond to market trends

In recent years, there has been a trend in California from harvesting hay in small hay bales of about 125 pounds to very large bales of 1,300 pounds or more. This shift is driven by both production considerations and the preferences of some consumers, but has significant implications for the hay market and its many consumer segments. We conducted a survey of rates and the rate-setting methods among custom alfalfa hay harvesters in the northern intermountain region and the San Joaquin Valley. The results show that large bales are cheaper to produce than small bales.

Whole-farm nutrient balances are an important tool for California dairy farms

In terms of nutrient balances, modern dairy systems are more complex than ever before. Feed is the primary nutrient input on the average California dairy farm. Whole-farm nutrient balances are an important tool for evaluating the economic and physical viability of each dairy farm, improving nitrogen imbalances and complying with environmental regulations. This article discusses the concept of nutrient balances and variables affecting the improvement of nitrogen imbalances in California dairy systems.