Fumigation of Burrowing Rodents with Carbon Monoxide: A Comparison to Alternative Management Options

Pocket gophers and ground squirrels cause extensive damage to many crops. Pressurized exhaust injection devices are increasingly used for managing these rodents, although no data were available to support their use. Therefore, we established a study to: 1) determine the efficacy of pressurized exhaust machines for pocket gopher and ground squirrel management, 2) compare these results to other burrow fumigant options, and 3) compare their cost effectiveness. Specifically, we tested two different pressurized exhaust machines for both ground squirrels and pocket gophers: Pressurized Exhaust Rodent Controller (PERC), and 2) Cheetah rodent control machine. For California ground squirrels, efficacy for the PERC machine was greater in moist soils (mean = 100%) than in drier soils (mean = 66%). Initial treatments using the PERC machine were more expensive than other burrow fumigation options, given the large cost of the machine. However, costs quickly dropped below that of gas cartridges (~44 days), and eventually dropped below that of aluminum phosphide if used extensively (~830 days). Efficacy for the Cheetah rodent control machine was far less encouraging for California ground squirrels, with results showing increased squirrel numbers at treatment sites (mean = +115%) post-treatment. For pocket gophers, aluminum phosphide (mean = 86%) and trapping (mean = 81%) proved to be more effective than PERC applications (mean = 56%) in heavy organic soils. We observed somewhat greater PERC efficacy in mineral soils (mean = 68%), suggesting potential variability in efficacy across soil types. At this point, the use of the PERC machine appears to be a viable option for inclusion into Integrated Pest Management programs for burrowing rodents where alternative options are limited; the Cheetah rodent control machine showed no utility for ground squirrel management in our study. More extensive testing of pressurized exhaust devices in differing soil types and under variable moisture levels is needed to determine their utility across a broader spectrum of treatment situations

SEQUENTIAL STOCHASTIC PRODUCTION DECISIONS FOR A PERENNIAL CROP: THE YIELD/QUALITY TRADEOFF FOR ALFALFA HAY

The "optimal cutting schedule" for alfalfa hay is described as a function of the trade-off between rising yield and falling quality of alfalfa over time and the local market prices being offered for different qualities of hay during the harvest season. Field test results quantify the yield/quality tradeoff for a California case study. A general decision rule is then derived to assist growers in making cutting decisions during a season. Finally, the optimal cutting schedule is shown to be the sum of sequential decisions for cuttings throughout the harvest season, with no schedule being best a priori.Crop Production/Industries,

Consejos sobre la sequía: Estrategias para cultivar alfalfa con agua limitada

Las condiciones de sequía requieren un enfoque completamente nuevo para la producción de cultivos y eso incluye a la alfalfa. Conozca cómo mantener las pérdidas de cultivos de alfalfa a un nivel mínimo durante un régimen de agua limitada

Monitoring Soil Moisture Helps Refine Irrigation Management

Soil moisture sensors can be used to determine the appropriate interval between irrigation, depth of wetting, depth of extraction by roots and adequacy of wetting. We tested the performance of soil moisture sensors in different crops. Sensors that read on a continuous basis, such as the Enviroscan device, can provide valuable information that may not be readily evident from periodic measurements. The Watermark blocks responded well throughout the wetting and drying cycles, indicating that they function more consistently over a wider range of soil moisture contents compared with tensiometers and gypsum blocks. Irrigation scheduling addresses the questions of when to irrigate and how much water to apply. Determining when to irrigate requires estimating the irrigation timing so that yield reductions will not occur due to excessive soil moisture depletions. One method for irrigation scheduling is to measure or monitor soil moisture content. This paper discusses methods for estimating when to irrigate and presents case studies of using various soil moisture sensors for irrigation scheduling. When should you irrigate? Available soil moisture is the water that plants can use. It is the difference between the field capacity moisture content and that at 15 bars (1,500 centibars), sometimes referred to as the permanent wilting point. Normally, recommended soil moisture tensions and allowable depletions are presented independent of climate and soil texture. However, research has shown that for cool, humid conditions, relatively large allowable depletions can occur before transpiration and yield are reduced. For warm, dry conditions, allowable depletions may be relatively small for the same soil type. Some incompatibility may exist between the two methods. A recommended tension of 70 centibars may deplete 60% to 70% of the available soil moisture in sandy soil, based on generic soil moisture release curves (not shown). In contrast, the 70-centibar recommendation may deplete only 15% to 20% of the available soil moisture in clay soil. However, a 50% allowable depletion in this soil may cause a soil moisture tension of 150 centibars. Which irrigation scheduling method is the best? The best method is that which maximizes crop yield. The recommended values in tables 2 and 3 reflect site-specific conditions, and thus some adjustment may be necessary for other soil types, salinity, climate, cultivars and cultural practices. Site-specific conditions under which recommendations were developed are not known, and thus any adjustments may require some trial-and-error. We developed the following guidelines using the recommended values in tables 2 and 3 and the generic moisture release characteristic curves: • For sand/loamy sand, consider using allowable depletions as the criterion for irrigating. Use of soil moisture tension may result in soil moisture depletions greater than allowable depletions. • For sandy loam/loam/silty loam soils, either method may be appropriate. Compatibility between the two methods is more likely for these soils. • For clay loam/clay soils, consider using allowable depletion as the criterion for irrigating. Use of soil moisture tension may result in small depletions. These recommendations are appropriate for low-frequency surface and sprinkler irrigation, where irrigation intervals are such that large soil-moisture depletions occur between irrigations. For high-frequency irrigation (microsprinklers, drip emitters and drip tape), small irrigation intervals recommended for these systems result in very small soil moisture depletions between irrigations. Therefore these recommendations do not apply for high-frequency irrigation. Methods of monitoring/measuring soil moisture include tensiometers, electrical resistance blocks, neutron moisture meter and dielectric soil moisture devices. Advantages of measuring/monitoring soil moisture include determining soil moisture depletions, adequacy of wetting from irrigation, patterns of soil moisture extraction due to root uptake of water and trends in soil moisture content with time during the irrigation season. This information can also be used to validate other irrigation scheduling techniques. The following examples illustrate the type of information that can be obtained from monitoring/measuring soil moisture. Flood-irrigated walnut orchard We used Watermark blocks, gypsum blocks and tensiometers to evaluate flood or border irrigations of a walnut orchard planted on sandy loam

Switchgrass is a promising, high-yielding crop for California biofuel

Ethanol use in California is expected to rise to 1.62 billion gallons per year in 2012, more than 90% of which will be trucked or shipped into the state. Switchgrass, a nonnative grass common in other states, has been identified as a possible high-yielding biomass crop for the production of cellulosic ethanol. The productivity of the two main ecotypes of switchgrass, lowland and upland, was evaluated under irrigated conditions across four diverse California ecozones - from Tulelake in the cool north to warm Imperial Valley in the south. In the first full year of production, the lowland varieties yielded up to 17 tons per acre of biomass, roughly double the biomass yields of California rice or maize. The yield response to nitrogen fertilization was statistically insignificant in the first year of production, except for in the Central Valley plots that were harvested twice a year. The biomass yields in our study indicate that switchgrass is a promising biofuel crop for California

A Multidisciplinary Investigation of a Polycythemia Vera Cancer Cluster of Unknown Origin

Cancer cluster investigations rarely receive significant public health resource allocations due to numerous inherent challenges and the limited success of past efforts. In 2008, a cluster of polycythemia vera, a rare blood cancer with unknown etiology, was identified in northeast Pennsylvania. A multidisciplinary group of federal and state agencies, academic institutions, and local healthcare providers subsequently developed a multifaceted research portfolio designed to better understand the cause of the cluster. This research agenda represents a unique and important opportunity to demonstrate that cancer cluster investigations can produce desirable public health and scientific outcomes when necessary resources are available

A Review of Events That Expose Children to Elemental Mercury in the United States

Concern for children exposed to elemental mercury prompted the Agency for Toxic Substances and Disease Registry and the Centers for Disease Control and Prevention to review the sources of elemental mercury exposures in children, describe the location and proportion of children affected, and make recommendations on how to prevent these exposures. In this review, we excluded mercury exposures from coal-burning facilities, dental amalgams, fish consumption, medical waste incinerators, or thimerosal-containing vaccines. We reviewed federal, state, and regional programs with data on mercury releases along with published reports of children exposed to elemental mercury in the United States. We selected all mercury-related events that were documented to expose (or potentially expose) children. Primary exposure locations were at home, at school, and at others such as industrial property not adequately remediated or medical facilities. Exposure to small spills from broken thermometers was the most common scenario; however, reports of such exposures are declining. The information reviewed suggests that most releases do not lead to demonstrable harm if the exposure period is short and the mercury is properly cleaned up. Primary prevention should include health education and policy initiatives

Evaluation of a Pressurized Exhaust Device to Control Pocket Gophers and Belding’s Ground Squirrels in Alfalfa

Intermountain alfalfa fields are ideal habitat for burrowing rodents like pocket gophers and Belding’s ground squirrel, due to an alfalfa stand life of at least 5 to 7 years and sprinkler rather than flood irrigation. Current control measures are only marginally effective and are expensive or extremely labor intensive, so many alfalfa producers have no rodent management program whatsoever. A new device called the Pressurized Exhaust Rodent Controller (PERC) was developed to control burrowing rodents using an internal combustion engine to generate and pressurize carbon monoxide that is injected into the burrow system using multiple hand-held probes. Field trials were conducted in April and May 2006 to evaluate the effectiveness of this device for controlling both pocket gophers and Belding’s ground squirrels in Siskiyou County, CA. An additional gopher control study was conducted in October 2011 to evaluate a newer version of the PERC device. Gopher studies were conducted in three commercial alfalfa fields and ground squirrel studies in an alfalfa field and a dryland range field. The PERC unit was used to inject exhaust fumes into the gopher burrow system. Approximately 24 hours after treatment, the gopher burrow systems were opened. Control was estimated by assessing the number of burrow systems that remained open the following day. Using the open-hole index technique to assess gopher activity, control efficacy was calculated to be 61%, 63%, and 45% for the two 2006 studies and the 2011 study, respectively. In the Belding’s ground squirrel studies, the hand-held probes were inserted into the open burrows and the burrow opening closed with soil prior to injecting the carbon monoxide exhaust. Control was assessed by determining the percentage of burrow systems that were reopened the day after treatment. Control efficacy for the two squirrel studies was calculated to be 81% and 71%. These preliminary results suggest that the injection of pressurized exhaust in gopher and squirrel burrow systems may be effective as part of an integrated vertebrate pest management program, but additional research is needed to further define the parameters required for effective control

THE ECONOMICS OF MANAGING BELDING’S GROUND SQUIRRELS IN ALFALFA IN NORTHEASTERN CALIFORNIA

We used estimates of yield loss from 1995 to 1999 and the reported costs and effectiveness of available control methods to provide a basis for developing a cost-effective management strategy for Belding’s ground squirrels in alfalfa in northern California. Mean annual losses varied between US$110/ha and US$300/ha of alfalfa. Growers usually spend less than US$25/ha on control methods that are implemented haphazardly and provide poor control. We suggest that growers can afford to spend more on control methods such as burrow fumigation or exclusion fencing that previously have been viewed as being too expensive. Control efforts should be focused on new fields supporting low-density populations