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Open Access Publications from the University of California

Scholarly Works (19 results)

  • Article
Proceedings of the Vertebrate Pest Conference, Volume 25 (2012)
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 An additional gopher control study was conducted in October 2011 to evaluate a newer version of the PERC device.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.
    Cover page: Evaluation of a Pressurized Exhaust Device to Control Pocket Gophers and Belding’s Ground Squirrels in Alfalfa
    • Article
    Proceedings of the Vertebrate Pest Conference, Volume 26 (2014)
    The pocket gopher is one of the most damaging vertebrate pests in California and throughout much of North American. Many options are available for managing pocket gophers including the use of rodenticides, burrow fumigation, and trapping. Trapping can be time consuming and labor intensive in some situations, but the efficacy of this approach can often offset these negative attributes. As such, we have engaged in several research projects over the last 5 years to increase the utility and effectiveness of trapping as part of an Integrated Pest Management (IPM) program for pocket gopher control. When comparing traps, we found that the Gophinator trap was a more effective trap than the Macabee, particularly when trapping larger pocket gophers. There does not appear to be a substantial benefit to covering trap-sets in most situations, but if trapping when temperatures are high, covering trap-sets may provide a slight increase in capture efficiency. If covering trap-sets, utilizing peanut butter might provide a slight increase in capture success; attractants provide no benefit if using uncovered trap-sets. Trapping was a highly effective technique for managing pocket gopher populations in crop fields. Furthermore, only 3 days were required for novice trappers to become efficient at capturing pocket gophers, although additional experience does increase the rate of capture. Collectively, these results validate the importance of including trapping in an IPM program, and should benefit all individuals who utilize trapping for managing pocket gopher populations.
      Cover page: Understanding Trapping as a Tool to Manage Pocket Gophers
      • Book
      • Peer Reviewed
      Farm (2011)
      Alfalfa is California's largest user of agricultural water, with about 1 million acres in production most years. When there's not enough water around, it can hit alfalfa growers hard. Here are some strategies that will help you weather a drought.
        Cover page: Drought Irrigation Strategies for Alfalfa
        • Book
        • Peer Reviewed
        Farm (2015)
        Irrigated perennial pasture grasses are the foundation of many crop and livestock enterprises. They are especially important during drought when the productivity of annual rangelands is compromised and cattle producers are in dire need of alternative forage sources. However, forage crop yields are highly influenced by drought because nearly the entire aboveground biomass is harvested. Production systems that maximize forage production and pasture survivability in drought years are of utmost importance.
          Cover page: Drought Tip: Managing Irrigated Pasture during Drought
          • Book
          • Peer Reviewed
          Farm (2018)
          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.
            Cover page: Consejos sobre la sequía: Estrategias para cultivar alfalfa con agua limitada
            • Book
            • Peer Reviewed
            Farm (2015)
            Drought conditions require a whole new approach to crop production, and that includes alfalfa. Learn how to keep alfalfa crop losses to a minimum under a limited-water regime.
              Cover page: Drought Tip: Drought Strategies for Alfalfa
              • Article
              • Peer Reviewed
              California Agriculture, Volume 56, Issue 6 (2002)

              Harvest timing has a profound effect on the yield and forage quality of alfalfa hay. Early harvest results in low yield but high forage quality and price, while delayed harvest increases yield but reduces forage quality and price. Since gross revenue is a function of both yield and price, it is important for growers to select the optimum cutting schedule. We quantified a biological relationship among yield, forage quality and day of harvest, using the results from 2 years of field studies at locations in the intermountain alfalfa production region of California. An economic analysis, including a decision model, was developed to enable producers to assess current market conditions and seasonal effects, and in turn select the most profitable harvest timing. Our analysis demonstrated that no single harvest strategy is always best. The most profitable approach depends on the rate of change in yield and quality for that season and the current price differential between the quality market classes for alfalfa hay.

                Cover page: Proper harvest timing can improve returns for intermountain alfalfa
                • Article
                Proceedings of the Vertebrate Pest Conference, Volume 28 (2018)
                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.
                  Cover page: Fumigation of Burrowing Rodents with Carbon Monoxide: A Comparison to Alternative Management Options
                  • Book
                  • Peer Reviewed
                  Farm (2006)
                  Part 10 of the 14-part Small Grain Production Manual covers the use of small grains as livestock forage, including choosing among the small grains, harvest stages and methods, and effect of maturity on yield.
                    Cover page: Small Grain Production Pt 10: Small Grain Forages
                    • Article
                    • Peer Reviewed
                    California Agriculture, Volume 72, Issue 1 (2018)

                    The Sustainable Groundwater Management Act (SGMA) of 2014 seeks to maintain groundwater discharge to streams to support environmental goals. In Scott Valley, in Siskiyou County, the Scott River and its tributaries are an important salmonid spawning habitat, and about 10% of average annual Scott River stream flow comes from groundwater. The local groundwater advisory committee is developing groundwater management alternatives that would increase summer and early fall stream flows. We developed a model to provide a framework to evaluate those alternatives. We first created a water budget for the Scott Valley groundwater basin and integrated the detailed, spatiotemporally distributed water budget results into a computer model of the basin that simultaneously accounted for groundwater flow, stream flow and landscape water fluxes. Different conceptual representations (using the MODFLOW RIV package and MODFLOW SFR package) of the stream–aquifer boundary provided significantly different results in the seasonal dynamics of groundwater–surface water fluxes. As groundwater sustainability agencies draw up plans to meet SGMA requirements, they must choose and test simulation tools carefully.

                      Cover page: Modeling guides groundwater management in a basin with river–aquifer interactions
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