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California pistachio growers have traditionally grown only one female cultivar (‘Kerman’) and one male pollenizer (‘Peters’). Starting in 2005, the UC breeding program released several improved cultivars, which are being planted on increasing acreage — and tested now under commercial conditions at multiple sites over multiple years. We conducted six experimental trials in the San Joaquin Valley to evaluate the performance of the UC cultivars ‘Gumdrop’, ‘Golden Hills’ and ‘Lost Hills’ and their associated UC male pollenizers ‘Famoso’, ‘Randy’ and ‘Tejon’ against the performance of the traditional pair, ‘Kerman’ and ‘Peters’. The new cultivars demonstrated a range of earlier bloom and harvest dates than ‘Kerman’ and some improved nut quality characteristics, such as a higher percentage of split, in-shell nuts. Results indicate that by growing the new female cultivars and synchronous pollenizers, producers can avoid the peak harvest period for ‘Kerman’, when equipment and processing facilities are limited, and maintain or improve their yield and nut quality.

Restoring habitat in retired farmland could reduce water demand and provide ecosystem services for farmers and local communities.

Wild pigs cause around $1 billion of damage to agriculture in the United States each year — foraging on crops, breaking branches and vines, and damaging irrigation lines and fences — but little is known about how and when they access agricultural fields. We used wildlife camera traps to document and describe wild pig access to two fenced southern San Joaquin Valley farms. Pigs breached fences around agricultural fields, especially during the harvest period when crops were ripe, and almost exclusively at night, outside of the regulated, daytime recreational pig hunting period. GPS data from an adult boar revealed that pigs may travel long distances from wildlands to reach crops. The results of our case study suggest that increasing monitoring and maintenance of fences during the harvest season and removing pigs that have learned to access farms may help reduce pig damage to agricultural fields. The results also suggest a formal scientific investigation of risk factors and strategies to reduce wild pig damage is warranted.

In the late 1990s, widespread outbreaks of Pierce's disease in grapevines were linked to transmission via the glassy-winged sharpshooter (GWSS), threatening California's multibillion-dollar table, raisin and wine grape industries. Government agencies responded to the crisis by implementing two control programs to manage GWSS. We analyzed the long-term economic impact of these two programs on citrus, grape and nursery producers. The net economic effects on all citrus producers and on grape producers in the southern San Joaquin Valley were insignificant, while all grape producers in the Temecula Valley saw an average increase in annual production costs of about $13.04 an acre. Based on our survey of nurseries in Southern California, approximately 11% had an infestation in 2008 and 2009, but only 3.0% in 2010. Average losses to nurseries per GWSS infestation were about $12,238. Nursery producers also undertook a variety of pest control methods to prevent infestations and plant losses, and to meet quarantine regulations. Average annual per-acre costs of these approaches were $2,975 for barrier methods to prevent GWSS from entering a premises, $1,032 in pesticide controls and $1,588 for in-house monitoring.

Research news Asian citrus psyllid and huanglongbing disease threaten California citrus Santa Clara San Benito Merced Madera Fresno Inyo Tulare Monterey Kings San Luis Obispo Kern M.E. Rogers A sian citrus psyllid is slowly spreading in California, and huanglongbing disease (also known as citrus greening) will likely become established in the state, requiring citrus farmers and residents with citrus in their landscapes to become ac- customed to a new reality. “Asian citrus psyllid and huanglongbing dis- ease have played out this way around the world, including in Florida, Texas and other states,” said UC Cooperative Extension specialist Beth Grafton- Cardwell. “There is no reason to believe California will be immune to the natural progression of this dis- ease complex.” The aphid-sized Asian citrus psyllid was first iden- tified in California in 2008 and is currently found in Imperial, San Diego, Los Angeles, Orange, Riverside, and San Bernardino counties. Asian citrus psyllid injects a toxin when it feeds on citrus leaves or stems, causing shoot deformation and plant stunting. Of greater concern is the fact that it vectors the bacterium associated with huanglongbing disease. Every tree infected with the pathogen will suffer a premature death, sometimes in as little as 3 years. But that doesn’t mean UC researchers and UC Cooperative Extension specialists and advisors are Asian citrus psyllid carries the vector of huanglongbing disease, also known as citrus greening. One symptom of the disease is mottling and chlorosis of leaves. giving this serious citrus disease free rein in the Golden State. UC is working with officials from the citrus industry, U.S. Department of Agriculture and California Department of Food and Agriculture (CDFA) to wage an all-out battle. They aim to contain psyllid populations, catch the infection early in order to rapidly remove infected trees, and monitor commercial citrus using geospa- tial technology. Meanwhile, scientists in university laboratories are exploring the trees, the pest and the pathogen at the molecular and genetic levels to find a long-term cure, while advisors are engaging and educating the public to help in the fight against the disease’s spread. Spread of the psyllid San Bernardino In March 2012, huanglongbing disease was de- tected in California for the first time. The multigrafted citrus tree in a Los Angeles County backyard was destroyed, but it is likely there are more infected trees nearby or in other areas. The disease is also spreading Riverside Orange northward in Mexico toward California. The psyllid and disease together present a grave ACP Observations Imperial threat to California’s $2.1 billion citrus industry, the Commercial Citrus San Diego livelihood of citrus farmers and thousands of farm- Counties workers, and the fragile economies in California’s rural citrus belt, extending from San Diego through Asian citrus psyllid total trap count, 2008–2012. The Geographic Information Systems Facility interior and coastal Southern California and up at the UC Kearney Agricultural Research and Extension Center in Parlier has entered a into the San Joaquin Valley. Their presence prevents partnership with the Citrus Research Board and CDFA to develop a statewide citrus mapping database, enabling the citrus industry to make strategic responses to ACP and HLB outbreaks. exports to countries that do not have this pest and To date, the database has mapped 29,865 Asian citrus psyllid detections. disease. The loss of citrus trees in urban areas of Santa Barbara Ventura Los Angeles http://californiaagriculture.ucanr.edu • October–December 2012 127

We compared standard tillage (ST) and conservation tillage (CT) for tomato and cotton production systems, with winter cover crops (CC) and without (NO), in Five Points, Calif., from 1999 to 2003. Conservation tillage reduced tractor trips across the field by 50% for tomatoes and 40% for cotton compared to standard tillage. When averaged over the 2001 to 2003 period (when the conservation tillage systems were established), tomato yields in CTNO were 6 to 8 tons per acre higher than the other treatments. In cotton, the STNO cotton yields during this period were the highest of all treatments and were 276 pounds per acre higher than the CTNO system. In-field dust concentrations were also significantly reduced by conservation tillage. Our results suggest that conservation tillage may be a viable alternative for managing tomato and cotton crops in the San Joaquin Valley, but that fine-tuning of the systems is needed.

Tillage operations, including preplant soil preparation, in-season weed control and postharvest stalk management, can account for 25% or more of overall cotton production costs. These operations reduce soil organic matter and contribute to air pollution. Conservation tillage practices similar to those used successfully elsewhere in the Cotton Belt may be a viable means for increasing profitability and improving soil in San Joaquin Valley cotton fields. In a comparison of reduced-tillage production methods, conservation tillage planting and stalk-management systems had yields comparable to those of standard tillage practices in two back-to-back cotton crops in Riverdale, Calif. These reduced-till systems decreased the number of tractor operations by 41% to 53%, fuel use by 48% to 62%, and overall production costs by 14% to 18%.

Boron deficiency of grapevines occurs occasionally on the east side of the San Joaquin Valley. Its symptoms include shot berries, shoot-tip dieback and leaves with yellowish mottling between veins. Boron must be applied carefully because the range between deficiency and toxicity is narrow. Our research evaluated the safety and efficacy of boron fertigation of grapevines using drip irrigation. Applying boron annually at 1/3 pound per acre to a moderately deficient vineyard elevated tissue levels into the adequate range within 2 years. However, the amount of boron used in a fertigation maintenance program will vary with leaching potential. Blade samples should be routinely monitored following fertigation and fertilizer amounts adjusted accordingly to avoid boron toxicity or deficiency.

This study evaluated the potential for subsurface drip irrigation in processing tomato to reduce subsurface drainage, control soil salinity and increase farm profits in areas affected by saline, shallow groundwater. Subsurface drip irrigation systems were installed in three fields of fine-textured, salt-affected soil along the West Side of the San Joaquin Valley. No subsurface drainage systems were installed in these fields. Yield and quality of processing tomato were compared with sprinkler irrigation systems. Yields increased 5.4 tons per acre to 10.1 tons per acre in the drip systems with similar amounts of applied water. The solids content of drip-irrigated processing tomato was acceptable. Water-table levels showed that properly managed drip systems could reduce percolation below the root zone, reducing subsurface drainage. Yields of the drip systems were also similar over a range of soil salinity levels.

The olive fruit fly was detected in Southern California in October 1998. This nonnative pest, which can render fruit unmarketable, has since moved throughout California and is now believed to be present wherever olives are grown in the state. Seasonlong trapping of adult flies in the San Joaquin Valley, and Ventura and Santa Barbara counties in 2001 and 2002 showed similarities in seasonal phenology, but also differences primarily due to varying temperatures and fruit availability. In the San Joaquin Valley, fly activity declined as maximum daily temperatures rose above 90°F, but increased when temperatures were between 70°F and 85°F. On the Southern California coast, the combination of available, susceptible fruit and moderate climate throughout the year may allow continuous reproduction of OLF with six or perhaps even seven generations per year.

As concerns increase over changes in pesticide regulations, farmworker safety, surface and groundwater contamination and escalating costs and uncertainties associated with chemical controls, walnut growers need effective and cost-efficient ways to produce walnuts with minimal use of pesticides. This study compared the effectiveness of Biologically Integrated Orchard Systems (BIOS) with conventionally managed walnut orchards in the northern San Joaquin Valley from 1999 to 2001. We found no significant differences between BIOS and conventional blocks in nut quality or yields. Codling moth was effectively controlled by pheromone disruption and alternative pest-control methods. Mating disruption, by itself, appears to provide good control of codling moth in many orchards. However, it is still more expensive for growers than conventional pest-control methods.

Central San Joaquin Valley farmers have been working with researchers and consultants to evaluate soil and crop management practices, enhance biologically integrated pest management and facilitate information exchange through the West Side Biologically Integrated Farming Systems (BIFS) Project. As part of this project, the amounts and composition of aboveground bio-mass in postharvest residues of typical rotational crops of the region were surveyed from 1996 to 1998. Crop residue biomass ranged from 9,560 pounds per acre for corn following grain harvest to 570 pounds per acre for onions. A very large range of organic matter recycling thus results from the various intensive cropping strategies that are currently used in this region.

Salt is currently being transported into the San Joaquin Valley via rivers and irrigation water at about three times the rate that it is being removed, endangering the productivity of agricultural land. As a possible salt-management solution, the San Joaquin Valley Drainage Implementation Program seeks to reuse saline water, such as tile drainage water or shallow well water, in crop production. Sugarbeet is a deep-rooted, salt-tolerant crop that can be used as part of a cyclic reuse program to reduce drainage-water volume and conserve high-quality water. Although sugarbeets grown with saline water produced adequate yields on test plots, sugar percentages declined because nitrogen also was present in the irrigation water source. For this reason, irrigating sugarbeets with alternative water sources is more complex, requiring accounting of nitrogen in reused water together with soil nitrogen to assure adequate crop quality.

A study conducted in 1995 reveals farmworkers are generally content with their jobs. Seasonal and year-round workers in orchard, vineyard, vegetable, agronomic, dairy and livestock operations in the Northern San Joaquin Valley were interviewed. Workers were generally complimentary to both supervisors and farm employers. One worker summed it up best, when he explained that he loved the job but it would be perfect if it paid better. An important implication is that workers may not necessarily be looking for work outside of agriculture. The 265 survey participants did, however, suggest numerous changes that supervisors and farm employers can make to improve the working conditions of agricultural laborers. Their suggestions included treating workers with more respect, constructive criticism of job performance, reasonable work pace and complete job instructions.

The Grasslands Bypass Project in the western San Joaquin Valley of California was conceived as a means of diverting selenium-contaminated agricultural drainage water from fresh water channels serving Grassland wetlands. Use of the federally owned San Luis Drain was made contingent on the formation of a regional drainage management authority by the project proponents and compliance with strict monthly and annual selenium-load targets and agreement to strict monthly and annual selenium-load targets for discharges from the 97,000-acre (44,000 hectares) project area. During the first year of this 5-year project, the Grasslands Basin farmers were successful in reducing selenium export from the project area by 44% and 33% when compared to water years 1995 and 1996. Although monthly targets were exceeded during the spring months of 1997, in part due to unusually high rainfall runoff from the project area and upper watershed, the goals of the project were met. There is popular sentiment that more was learned about selenium drainage management and achieved in selenium load reductions by participating water districts during the first year of the project than in the past decade.

Growth and development pressures and environmental regulations are forcing dairy enterprises in the Chino Valley to relocate. Alternative areas for producing raw milk for the Los Angeles–San Diego basin will be needed. Two areas of particular interest are the Imperial and Palo Verde valleys. For the scenario studied, milk can be produced in the Imperial Valley at least as efficiently and cheaply as in the southern San Joaquin Valley. Transportation costs will determine profitability. Establishing a viable dairy industry in the Imperial Valley will also depend on the size of herds, the establishment of milk processing plants and the regulatory environment that surrounds it.

Red color development is an important factor for consumer acceptance of California "Fuji" apples. Several attempts to improve red color development, including delaying harvest, have been unsuccessful in warm production areas. In California, late harvest has been associated with physiological problems such as skin cracking and internal browning. A study conducted under the warm San Joaquin Valley conditions reveals a new approach to economically enhance "Fuji" red color. The use of reflective materials between tree rows enhanced red color development without reducing fruit quality under poor and good orchard conditions.

Basal leaf removal, which has been used to reduce damage from bunch rots and seasonal leafhopper infestations, was tested for its effects on powdery mildew in the San Joaquin Valley. Powdery mildew is one of the most damaging diseases of wine grapes in California. On-farm experiments showed that leaf removal reduced the disease in two of five experiments and facilitated improved spray coverage in grapevine fruiting zones. Leaf removal can improve the effectiveness of fungicide programs in reducing powdery mildew damage, but should not be relied upon alone to control the disease.

California almond growers commonly use organophosphate pesticides, which can be disruptive to biological control. Sprays during the spring and summer kill beneficial arthropods, including parasitic and predatory insects and spiders. In addition, pesticides have been detected by Cal EPA in winter fog and in runoff water flowing into the rivers of the San Joaquin Valley, which may lead to further restrictions in pesticide use. However, some almond growers are able to grow nuts with low insect damage without using toxic insecticide sprays. This article reports the results of a 6-year study, begun in 1988, of three almond orchards in Merced County to identify grower practices that permit reduced pesticide use.

Codling moth and rosy apple aphid limited production and profitability in the organic Granny Smith apple production system in the northern San Joaquin Valley. Over the course of this 4-year study, organic techniques were developed to control codling moth, but not rosy apple aphid, which is an occasional pest. Fertility was easily maintained in the organic system with leguminous cover crops, which also served as a habitat for insects beneficial to apple production.

Pheromone confusion worked best in isolated orchards with low codling moth populations. In areas where codling moth developed three to four generations and apples were exposed to egg laying for each generation, mating disruption with pheromones was not consistently successful in suppressing codling moth populations. For an orchard with an established history of codling moth infestation, well-timed insecticide sprays had to be integrated with the confusion technique to obtain adequate control.

The California Ozone Deposition Experiment, using Instruments mounted In an airplane and on the ground, shows that agricultural land in the San Joaquin Vailey removes large amounts of ozone from valley air. The most active pathway Is uptake through sto-mata In plant leaves, the process leading to crop yield losses. Other pathways, Including ozone destruction on leaf, stem and soil surfaces, are slower but very important on a valley-wide basis. Ozone deposition to crops may have a slgnlflcant Impact on air qualify, and should be considered when farmland Is converted to urban uses that contribute more to ozone production and less to ozone removal.

Since the 1950s growers have routinely used soil fumigants such as methyl bromide (MBr) and 1,3-dichloropropene (1,3-D) before replanting orchards and vineyards. Fumigants double plant growth in the early years after replanting and provide several years of nematode relief when resistant rootstocks are unavailable. However, the recent suspension of 1,3-D and the mandated phase-out of methyl bromide by 2001 have clouded the future of fumigant use. To develop alternatives, we must first document the pest control value and plant growth benefit of fumigation. Over the last decade, we have initiated several 2-year field trials in replant sites in the San Joaquin Valley. Our results quantify fumigation benefits and point to the feasibility of some alternatives, including a portable soil drencher.

The domestic and world market for grape juice concentrate is growing. We discuss several options that may enable the San Joaquin Valley's grape industry to capture a larger share of this growth market.

During summer, especially in pistachio orchards irrigated with high-trajectory-angle sprinklers, sprinkler water spreads fungal inocula of Botryosphaeria blight disease to fruit clusters, shoots and leaves. In tests, altering the sprinkler irrigation trajectory angle from 23 degrees to 12 degrees prevented release and spread of spore inoculum and significantly reduced the disease in three commercial pistachio orchards in the Sacramento and San Joaquin valleys.

Only one-fifth of the drainage-impacted lands in the San Joaquin Valley's west side discharge their irrigation return flows into the San Joaquin River. One option for the remaining lands is to dispose of drainage waters in evaporation ponds. Eventually, the evaporite salts that form in these ponds must also be removed. In some cases, these evaporites could constitute hazardous wastes.

In the spring of 1991, a water quality model was used to predict flows and salinity in the San Joaquin River for the following summer. It was predicted that the flows and salinities should be more favorable than in 1977, primarily due to improved water quality in the Tuolumne River and increased flows in the Stanislaus River. Actual levels would be largely determined by the amount of diversions from the river.*

A hardwood rangeland classification system for California is described. The system provides private landowners, land managers, and researchers a unifying framework from which known ecological and management information can be retrieved. Standardization of type names facilitates the exchange of information on hardwood rangelands within and among agencies, landowners, and universities. The dichotomous keys to the type descriptions ensure that the system is field oriented and user-friendly. The classification system consists of 57 subseries arranged hierarchically within 7 Series. The oak series are defined by the dominant oak species present on the site. A Mixed Oak Series is also defined from sites that contain three or more species of oak at constancies of greater than 30%. This system does not include subseries descriptions for Engelmann or garry oak types. The classification system was developed from approximately 4,300 plots collected as part of the Vegetation Type Map (VTM) survey conducted during the 1920s-1940s by the USDA Forest Service, Pacific Southwest Forest and Range Experiment Station, and approximately 500 plots collected as part of the Forest Inventory conducted by the USDA Forest Service, Pacific Northwest Research Station in the 1970s and 1980s. The base information on species composition, percent cover by species, tree stand structure, and environment was collected on 1/5-acre plots. Species cover was determined from a 33' by 66' belt transect on each plot. The classification structure was developed using TWINSPAN, a polythetic, divisive classification program developed by Hill (1979a). Further analyses were performed using DECORANA, and frequencies, regression, and analysis of variance. The information contained in the final type descriptions was developed from VTM data only. The keys and type descriptions have been field tested and verified at several locations in the State, such as Hopland Field Station, Sierra Field Station, Hastings Reserve, and the San Joaquin Experiment Station. The tests were conducted by individuals familiar with hardwood rangeland ecosystems and those who were not. Ongoing use of the keys and descriptions in other parts of the State will provide information for further refinement of keys and descriptions. Additional information on potential productivity and response to management will be incorporated into the descriptions by users as they identify the types that they are working in by the classification subseries names.

The silverleaf whitefly (formerly "sweetpotato whitefly strain B," see p. 7) has caused extensive damage in Southern California's Imperial, Coachella, and Palo Verde valleys. It is now present in the San Joaquin Valley and is raising increasing concern among California's agricultural interests.

Cotton yield data collected from 32 fields in the Broadview Water District are negatively correlated with several measures of soil salinity, sodicity, and irrigation uniformity. Results suggest that farmers may be able to increase cotton yields by improving irrigation uniformity on surface-irrigated fields.

Pheromone traps in the San Joaquin and Sacramento valleys indicate that seasonal patterns of the tomato fruitworm are similar across large areas. Catches were greatest late in the season. A non-pest species (false corn earworm), also captured at all locations, is easily confused with the pest.

Policies to reduce agricultural drainwater in the San Joaquin Valley are complicated by different existing drainage conditions on farms. Drainwater reduction policies that address such variations will be more efficient in achieving regional drainage goals.

The likelihood of global warming and its potential consequences are major concerns to global climate researchers, government officials, and members of the public. Conferences, workshops, and various publications have considered the effects of higher global temperatures on ocean levels, rainfall, and other climatic variables.

Each year, irrigation runoff from West Stanislaus County farmland carries about 1.2 million tons of sediment into the San Joaquin River. The sediment contains pesticide residues which threaten aquatic wildlife. One solution for this problem is to inject polyacrylamide polymers into irrigation water, a practice which reduces soil erosion and has economic benefits to the grower, such as increasing infiltration rates. In recent trials, this practice reduced soil erosion and runoff water from a furrow-irrigated spinach field. Polyacrylamide-treated furrows had a 10% lower outflow rate than the untreated furrows. In addition, the polyacrylamide flocculated the suspended soil particles; on average, 99.7% settled out compared to soil particles in untreated furrows.

Not Available – First paragraph follows: The conflict over water diversions from the Sacramento-San Joaquin Delta has been one of the longest and most severe of California's water wars. This conflict developed in 1951 when the massive pumps of the federal Central Valley Project began pumping water from the south Delta to supply water to San Joaquin Valley farms.

This paper analyzes optimal management strategies for farms with limited natural drainage and no access to off-farm disposal facilities. A representative farm with conditions typical of a drainage problem area in the San Joaquin Valley is considered, using a long-run steady-state model. Optimal, profit-maximizing water applications were significantly less for this farm than would be profitable for a farm with no drainage problems. Relatively high yield levels were maintained, and the required pond size was relatively small. Comparatively little crop switching occurred relative to that on a farm with unlimited natural drainage, and drainwater reuse was not profitable when all costs were considered. Access to an off-farm disposal facility brought significant benefits, and a moderate discharge fee significantly reduced effluent volumes. A plausible amount of underground drainage flow to the farm had little effect. With uniform water applications, returns to land and management are significantly greater than with non-uniform applications, and the pond size is almost negligible. Water application levels are almost identical in the limited and unlimited drainage cases, when water is applied uniformly.

The content of total, nitrate, fixed, exchangeable, and organic nitrogen in Cretaceous and Tertiary formations in two representative drainage basins of the east central Diablo Range was determined. The results of these analyses showed that high concentrations of organic nitrogen (up to 1,200 ?g/g) occur predominantly in the Cretaceous formations while high concentrations of nitrate (up to 4,800 ?g/g) occur predominantly in the younger Tertiary sediments. The concentrations of fixed and exchangeable ammonium were variable and generally low. Available geomorphic data for the western side of the San Joaquin Valley were analyzed to seek a possible cause for the observed large accumulations of nitrates in west side soils. It was concluded that the occurrence of mudflows and intermediate flows in the alluvial fans bordering the Diablo Range on its east side, in conjunction with a semi-arid climate, is the principal factor responsible for the retention of soluble nitrogen. A method for predicting high nitrate soils in the western San Joaquin Valley was developed by assigning a score to each basin and associated fan based on the occurrence of high nitrate formations, the percentage of fine-grained sediments, and the predominance of mudflow deposits.

A model of the flight phenology of the beet armyworm (Spodoptera exigua Hubner) was constructed using a combination of laboratory and field experimentation. The model incorporates the following relationships: 1) developmental rates of immature stages as linear functions of temperature, 2) age-dependent immature mortality rates, 3) age-dependent oviposition rates, 4) age and temperature-dependent adult mortality rates, and 5) adult flight activity as a function of temperature. The model was used to examine beet armyworm flight phenology by simulating light trap catches. An extensive black light trapping program was conducted at five locations in three climatic regions within central California to provide a total of six data sets for these tests. Results of the simulations were generally favorable. When initialized with early season light trap data, the model was able to predict the patterns subsequently observed for the locations in the San Joaquin and Sacramento valleys, indicating that a good understanding of beet armyworm flight phenology in these regions was incorporated. The model did not reproduce observed patterns of flights in the cool Salinas Valley, however, indicating that one or more of the relationships in the model was not valid under the conditions of this region.

Four cotton varieties of genetically different growth and fruiting habits were grown on two widely different soils under three extremes of water management. Performances of the contrasting genotypes were evaluated in terms of yields, vegetative growth, and lint quality. Yields were influenced both by water management and variety, with an intermediate irrigation treatment generally most favorable. Low spring temperature reduced yields, especially on a soil having high water-retention capacity. Excessive irrigation caused rank growth in all varieties, but a significant variety-irrigation interaction was observed. Fiber quality was influenced by water management as well as by cotton variety. Less-frequent irrigation generally reduced fiber length in all varieties but the reduction was less for the two Acala varieties. Reduced frequency of irrigation lowered elongation percentage but increased fiber strength.

Populations of the sorghum midge, Contarinia sorghicola (Coquillett), are maintained at low levels in johnsongrass, Sorghum halepense (L.) Pers., from late spring to mid-summer. A slow buildup occurs on grain sorghum, S. bicolor (L.) Moench, during early August, and numbers capable of causing severe yield reductions are reached after ca. 20 August. Fields planted prior to 15 June will likely escape midge damage. Those planted between 15 and 22 June may or may not escape damage, depending on the season. Virtually all plantings made after 22 June risk severe midge infestations and yield reductions. Plant population appears to have little influence on ultimate yield. The yields in plots thinned to 13 and 26 plants per meter were not significantly different from those thinned to 39 plants per meter, although the midge infestation in heads from the low plant population was more than double that in heads from the high plant population. Plants in the low population produced larger heads and were able to tolerate a much higher level of infestation without suffering a yield reduction.

Subsurface drainage water of agricultural lands collected in tile lines may contain nitrate-nitrogen which serves to pollute surface waters. The objective of the research was to determine quantities and concentrations of nitrate-nitrogen in tile drainage and their relationship to soil, fertilizer input, crop, and time with respect to water applicaiton. The first research phase consisted of extensive monitoring of tile drainage effluents collected in important agricultural areas in California. More intensive investigation of nitrate-nitrogen within a few soil profiles was done during the second phase. Nitrate-nitrogen concentrations were not well-correlated with any measured parameter. The amount of nitrate-nitrogen contained in tile effluent was quite well-correlated with total water discharge and fertilizer nitrogen application. Higher amounts of nitrate-nitrogen were removed from coarse-textured soil profiles as compared to profiles containing a layer of fine-textured material. Some alluvial soils on the west side of the San Joaquin Valley apparently contain significant native nitrogen which contributes both to high nitrate-nitrogen concentrations and total mass emissions in tile effluent. Implications of the research findings to nitrogen and water management to achieve a desired water quality standard are discussed. It appears that the most positive approach to controlling nitrate-nitrogen in irrigated agriculture is through control of leaching.

does not appear. First page follows. Introduction At the confluence of the Sacramento and San Joaquin rivers in central California an area of about one quarter million acres, known as the Delta, is made up entirely of peat (fig. 1). These highly organic soils are said to comprise the second largest continuous body of peat land in the United States, exceeded only by the Everglades in Florida. With minor exceptions, the entire Delta has been reclaimed from tule swamp. In its present high state of cultivation, it produces farm products with an annual value of more than 25 million dollars. The area consists of a number of tracts and islands, each organized into one or more reclamation districts under state law for the construction, maintenance, and operation of levee and drainage systems. There are more than 80 reclamation districts in this area. Around the borders of the Delta the peat soils merge gradually into the adjacent mineral soils, or feather out in shallow depths of peat overlying mineral soils. The center of the Delta is composed of islands which are entirely surrounded by the interlacing channels of the two major rivers. In portions of this area the peat is 30 feet or more in depth. All of the channels surrounding the islands are navigable to barges and other freight-carrying craft. Cultivation in the Delta region dates from the passage of the Swamp and Overflow Act of 1850, when title to these lands passed from the federal government to the state. The first levees were low dikes, truly handmade by Chinese labor with wheelbarrows and shovels. The early reclamation, therefore, did not penetrate deeply into the heart of the peat lands. Prior to reclamation, the entire area was covered with a dense growth of tule (Scirpus lacustris), with a fringe of willows and other woody plants along the slightly higher stream banks, where the soil contains the greatest amount of mineral material. The surface of the area was at zero, or sea-level, elevation and was inundated at high tide or at flood stage in the rivers.

does not appear. First page follows. Introduction The lettuce crop is a very important one in California, and the product is shipped in considerable quantity throughout most of the year. The production of lettuce seed is also an important industry. While the variety New York is the only one produced for shipping fresh, almost all of the important varieties are grown for seed. The growing of lettuce for seed is confined almost entirely to the delta lands of the Sacramento and San Joaquin rivers and to the Santa Clara Valley. Wherever a large number of varieties are grown in close proximity, there arises constantly the question of the danger of cross pollination. Pollination investigations reported herein were initiated because of this question. The morphological studies reported in this paper were commenced to furnish information needed in order to prosecute more successfully other lines of investigation that have been started on lettuce. Material and Methods The lettuce seed used for growing the material for the morphological studies herein reported, was planted at the University Farm, Davis, California, in December, 1923. The variety employed was Iceberg. The material for study was killed in formalin-alcohol solution, then dehydrated and embedded in paraffin according to the usual procedure. Most of the sections were stained in Delafield’s haematoxylin, or safranin and gential violet.

does not appear. First page follows. Introduction Celery affected with yellows was first observed in the San Joaquin delta in 1925 during an investigation of economic plants naturally infected with curly top. During 1926 and 1927 an average of 5 per cent of the crop was affected in the delta, the most important celery producing region in California; in 1928 about 10 per cent of the celery showed symptoms of the disease. Some celery growers hoe out the diseased celery so that an exact percentage of yellows could not be obtained in some fields. During 1927, 7,000 acres of celery, valued at $3,096,310, were grown in the San Joaquin delta so that the loss due to yellows amounted to $154,815. During 1928, 7,400 acres of celery are being grown in the delta, but the value of the crop has not been estimated; the loss due to this disease will probably exceed $300,000. Lettuce yellows, known as white-heart or rabbit-ear in New York, and Rio Grande disease in Texas, is a rather serious malady of lettuce. Lettuce yellows is of no economic importance at present in California, but its nature is such as to demand field observations year after year to determine its potential importance.

does not appear. First page follows. Introduction The early history of the alfalfa butterfly as a pest is well covered in the works of (Wildermuth (1911), (1914), (1920).4 In California and other parts of the West the caterpillar of this butterfly, Colias eurytheme Boisduval,5 is the most serious pest attacking alfalfa. Here, in cases of severe outbreaks, entire fields are often defoliated. During the course of the alfalfa weevil investigation in the region adjacent to the San Francisco Bay and in the northwest portion of the San Joaquin Valley, it was observed that the amount of damage done by the alfalfa butterfly varied not only from year to year but from field to field. One of the reasons for this behavior came to light during September, 1938. In an alfalfa field near Tracy a large number of larvae were collected for use in toxicity studies. The alfalfa was about one third grown and supported a very large population of small larvae. At first it appeared that the developing population was sufficient to inflict serious damage. However, most of the larvae collected proved to be parasitized by a hymenopterous parasite, Apanteles flaviconehae Riley. (Wildermuth (1914)) probably referred to this parasite when he recorded A. fiavicombe as a relatively unimportant parasite of the alfalfa butterfly at Salt Lake City, Utah.

does not appear. First page follows. During 1918-1932 field investigations were carried on to determine where the beet leafhopper spends the winter and to locate the natural breeding areas in this state. Trips were taken to Death Valley, Mojave Desert, Imperial Valley, and the Tulare Lake and Bakersfieid sections of the San Joaquin Valley—areas from which Ball(2) believed the beet leafhopper migrated into sugar-beet fields—and also to the middle and northern sections of the San Joaquin Valley, to the Sacramento Valley, Santa Clara, and Salinas valleys, and to all other important sugar-beet districts in California. After a general survey of this enormous territory, it soon became evident that it would require many years of field work to map the natural breeding areas of this insect, and hence the work was limited to the San Joaquin, Sacramento, Santa Clara, and Salinas valleys and to several small valleys. No foothill investigation has been carried on in Death Valley, Antelope Valley, Mojave Desert, and Imperial Valley. Such results as were obtained in these districts have been published in previous papers.(28), (30), (40) The host plants of the beet leafhopper on the uncultivated plains and foothills, in the cultivated areas, and the original native host plants, the spring and summer dispersals and migrations, natural barriers, causes of fluctuation in population, and natural enemies were also observed during the investigations. Distribution of Beet Leafhopper The beet leafhopper is a native species and has been taken in western North America from Canada into Mexico. Davis(11) found the northern limit of the leafhopper was Cache Creek, British Columbia, 140 miles north of the international boundary. Carter(10) used the climograph as a means of comparing climates with respect to precipitation and temperatures in determining the probable limits of the range of the beet leafhopper; these studies were supplemented with surveys of the distribution of the insect. He considers that the presence of the leafhopper in British Columbia is due to a northward migration. Carter(9) published the results of the Canadian survey conducted by H. L. Seamans and states that the leafhopper was not found in the province of Alberta, although the results of the survey were not conclusive. Davis(11) found that the leafhopper was generally distributed in western Washington and Oregon.

Population studies in southern San Joaquin Valley vineyards showed that the distributional patterns of Willamette mite, Eotetranychus willamettei Ewing, and Pacific mite, Tetranychus pacificus, differ in the Valley, in the vineyard, and on the vine itself. Pacific mite generally does best under hot and dry conditions while Willamette mite prefers cooler and more humid conditions, although there is considerable overlapping of the two species. Detailed populations studies showed that untreated vineyards with no histories of pesticide treatment often exhibit more efficient levels of predation than do vineyards which have been treated. Also, contrary to the views of some investigators, these studies indicate that Metaseiulus occidentalis (Nesbitt) has no self-limiting aspects in its response to low or high prey densities. In undisturbed vineyards, a mild predator-prey interaction appears to help perpetuate effective control of low prey densities by M. occidentalis. In disturbed vineyards, widely fluctuating predator and prey populations may lead to population crashes and continuation of imbalance. Moreover, when regulating low, but potentially serious, Pacific mite densities in undisturbed vineyards, M. occidentalis appears to benefit from the presence of the less seasonally restricted Willamette mite. Tonnage and fruit-quality data showed that Willamette mite is often not a significant pest. Little differentiation has been made in the past between Pacific mite and Willamette mite, and treatments have been applied as if both were serious pests.

does not appear. First page follows. Introduction The strawberry rootworm, Paria canella quadrinotata (Say), is a serious pest of strawberries and raspberries in California. Its biology was studied intensively in the Santa Clara Valley from 1939 through 1942, when World War II, and the consequent reduction in berry acreage, caused work on the problem to stop. The results of the study of the strawberry rootworm are now reported in this paper. Since the-war there has been a marked increase in berry acreage, with an accompanying increase in actual and potential damage by the strawberry rootworm. Further studies were therefore conducted on control during the past three years, and these will be reported in another paper. Geographical Distribution The strawberry rootworm is probably indigenous to North America, since it has been reported only from the United States and Canada. Published reports indicate its presence in Alabama, Arizona, California, Connecticut, District of Columbia, Illinois, Indiana, Kansas, Louisiana, Maine, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Montana, Nebraska, New Jersey, New Mexico, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Tennessee, Texas, Virginia, and Wisconsin. From its known distribution, the pest may be assumed to occur throughout the entire United States. Its distribution in the United States is shown in figure 1. In California, the strawberry rootworm occurs in Alameda, Contra Costa, Merced, Monterey, Placer, Sacramento, San Benito, San Francisco, San Joaquin, San Mateo, Santa Clara, and Yuba counties.

The critical importance of water supply problems in the San Joaquin Valley indicates a need for reliable information on the possible effects of forests on accumulation, losses, and melting of snow on the west slope of the Sierra Nevada. The present study was made in part of the Stanislaus National Forest, and covered the seven years, 1934-38 and 1940-41. The aim was to find what kinds, sizes, and densities of forests are most effective in promoting accumulation of snow, in minimizing losses by evaporation, and in retarding and prolonging the period of melting. Recommendations for improved forest management in relation to water supply are made in the light of the findings for the seven seasons under study.