Josh Davy

Managing Medusahead (Taeniatherum caput-medusae) on Rangeland: A Meta-Analysis of Control Effects and Assessment of Stakeholder Needs☆

ABSTRACT Invasive plant response to control efforts is strongly modified by site-specific factors, treatment timing, and environmental conditions following treatment, making management outcomes challenging to predict. Systematic reviews, which involve quantitative synthesis of data, can address this challenge by identifying general patterns of treatment effects across studies and quantifying the degree to which these effects vary. We conducted a systematic review of medusahead (Taeniatherum caput-medusae [L.] Nevski) control treatments that couples a meta-analysis on control data with an assessment of stakeholder needs to identify critical medusahead management knowledge gaps. With the meta-analysis we generated effect size estimates of how combinations of herbicide, burning, seeding, and grazing impacted medusahead on rangeland dominated by either annual or perennial vegetation. All combinations of treatments in both rangeland systems provided significant short-term control of medusahead, although treatment effects were highly transient on perennial rangeland, particularly for seeding treatments. Stakeholders listed grazing as a preferred management tool, and on annual rangeland an almost twofold reduction in medusahead abundance was achieved by timing high stocking rates to match phenological stages when medusahead was most susceptible to defoliation. Insufficient data were available to evaluate effects of grazing on medusahead on perennial rangeland. On the basis of these data and our stakeholder survey, four major information needs emerged, including the need to better understand 1) seedbank response to burning and herbicide treatments, 2) how to optimize grazing animal impacts on medusahead given ranch enterprise constraints, 3) costs and benefits of control and risk of practice failure, and 4) impacts of adaptive management treatments conducted on larger scales and at longer time intervals. Addressing these knowledge gaps should help overcome key ecological and economic barriers inhibiting implementation of medusahead and other invasive plant management programs on rangeland and provide a positive step toward conserving the critical ecosystem services these systems provide.

Preemergent Control of Medusahead on California Annual Rangelands With Aminopyralid

Abstract Medusahead (Taeniatherum caput-medusae [L.] Nevski), the most problematic invasive grass on many California rangelands, is difficult to control selectively in grasslands. Prescribed burning, grazing, and herbicides have been tested with some success but are not practical in all situations. The selective herbicide aminopyralid, normally used for control of certain broadleaf species such as thistles, suppresses some annual grasses when applied pre- or early postemergence. In 2009–2010, we tested the efficacy of aminopyralid for medusahead control in preemergence applications at three foothill rangeland sites in northern California. We compared a rate series of aminopyralid (53, 88, 123, and 245 g · ha−1 acid equivalent [ae]) with rimsulfuron (18 and 35 g · ha−1 active ingredient) and imazapic (140 g · ha−1 ae). Plots were 3 × 9 m with four replications at each site. Treatments were applied in early fall 2009. In May 2010, we took visual cover estimates and biomass/seedhead samples in three quadrats per plot. In regression analysis, medusahead cover was found to decrease consistently with increasing rates of aminopyralid. Medusahead control at the highest rates of aminopyralid was consistent across the three sites, averaging 89% ± 3 standard deviation (SD) with 245 g · ha−1 ae and 59% ± 10 SD with 123 g · ha−1 ae. Aminopyralid at lower rates, rimsulfuron, and imazapic were less consistent. Cover of other annual grasses increased in plots treated with aminopyralid at all sites. Aminopyralid has potential utility for suppressing medusahead, particularly in sites also infested with invasive members of the Asteraceae. However, the most effective rate (245 g · ha−1 ae) is registered for use only as a spot application. In situations where this rate can be justifiably used, it would be expected to give season-long control of medusahead, as well as longer-term control of thistles and other susceptible species. Resumen Medusahead (Taeniatherum caput-medusae [L.] Nevski), la especie de pasto invasiva más problemática en muchas áreas de California, es difícil de controlar selectivamente en los pastizales. Se ha probado el fuego prescrito, el pastoreo, y los herbicidas con algo de éxito pero no son prácticos en todas las situaciones. El herbicida selectivo aminopyralid, normalmente usado para el control de ciertas especies de hoja ancha como cardo, suprime algunos pastos anuales cuando se aplica durante la etapa de pre o al inicio de pos-emergencia. In 2009–2010 se evaluó la eficiencia de aminopyralid para controlar medusahead en aplicaciones pre-emergentes en tres sitios localizados en pastizales del norte de California. Se compararon una serie de rangos de aplicación de aminopyralid (53, 88, 123, y 245 g · ha−1 acido equivalente [ae]) con rimsulfuron (18 y 35 g · ha−1 de ingrediente activo) e imazapic (140 g · ha−1 ae). Las parcelas fueron de 3 m por 9 m con cuatro repeticiones en cada sitio. Los tratamientos se aplicaron durante el inicio del verano de 2009. En mayo de 2010 se tomo una estimación visual de la cobertura y muestras de biomasa/inflorescencia en tres cuadrantes por parcela. En los estudios de regresión encontramos que la obertura de medussahead disminuyó consistentemente con el incremento en el rango de aplicación de aminopyralid. El control de medusahead bajo los niveles más elevados de aminopyralid fue consistente en los tres sitios, promediando 89% ± 3 SD con 245 g · ha−1 ae y 59% ± 10 SD con 123 g · ha−1 ae. La aplicación de aminopyralid a bajos niveles, rimsulfuron, e imazapic fueron menos consistentes. La cobertura de otras especies de pastos anuales se incrementó en las parcelas tratadas con aminopyralid en todos los sitios. Aminopyralid tiene un potencial para suprimir medusahead, particularmente en sitios infestados con los miembros invasivos de asterácea. Sin embargo, la tasa más efectiva (245 g · ha−1 ae) está documentada para uso solo de aplicación a un sitio específico. En situaciones donde esta tasa puede ser usada justificadamente, se esperaría que ofreciera control durante toda la temporada sobre medusahead así como control a largo plazo de cardos y algunas especies perenes.

Coping with Drought on California Rangelands

On the Ground Rangeland livestock producers were among the first agricultural communities affected by Californias multiyear drought. Rancher surveys and in-person interviews have identified key strategies for coping with and adapting to drought. Increasing flexibility, resource valuation, and information sharing are important components of building adaptive capacity. Web-based communication systems have provided new tools for peer-to-peer learning, public education, and extending knowledge to larger audiences. Insights from managers experiences are important for adaptation planning to enhance resilience of rangeland social-ecological systems to climate stresses.

Using Phenology to Optimize Timing of Mowing and Grazing Treatments for Medusahead (Taeniatherum caput-medusae)☆

ABSTRACT The invasive annual grass medusahead (Taeniatherum caput-medusae [L.] Nevski) poses a substantial threat to the health and function of rangelands across the western United States. On rangelands containing other desirable annual grasses, selective control of medusahead is difficult as this invasive species has traits similar to those of desired species. One key trait that differs between medusahead and other annual grasses is the rate and timing of phenological development. In this study we define management states for medusahead on the basis of the patterns of variation of forage palatability and susceptibility of seed production to defoliation over phenological stages. We integrate these management states with field observations to model the rates and timing of phenology-based management states to identify when targeted grazing or mowing treatments are most appropriate using Dirichlet regression and multistate modeling. While defoliation at any phenological stage from V3 (boot) to R8 (milk stage) was effective in reducing medusahead seed head production, clipping after anthesis almost eliminated seed production. However, the observed decline in crude protein at this point (11–8%) suggests that the transition from R4 (emergence of awns) to R5 (anthesis) is also the point at which medusahead becomes both unpalatable and not adequately nutritious to livestock. As a consequence there was a window of 10 to 15 days when 90% or more of medusahead reproductive tillers are susceptible to grazing but could also support nutritional needs of cattle and sheep to prevent avoidance in diet selection. In contrast, the window of opportunity for mowing, on average, extended for about 35 days. In a given year, the timing in which different medusahead populations entered each phenological stage varied at both the landscape and pasture scale, which creates both challenges and opportunities in using grazing animals and other defoliation mechanisms to control medusahead.

Mineral status of California beef cattle

Abstract Optimal mineral nutrition is required for cattle reproduction, immune function, and structural development. Formal evaluation of the current mineral status of California beef cattle is currently lacking. In 2017, a survey was initiated that evaluated a panel of 10 different minerals in 14 counties across California. Samples were collected from 555 cattle at 50 different ranches. Region of the state significantly affected herd mineral status. Herd use of supplements was also significant, and increased most blood levels of the mineral(s) targeted for supplementation. Forage source was idiosyncratic on its effect of mineral status. Previous blood survey data showed selenium to be widely deficient in California cattle in the 1970s and 1980s, but in this case, it was generally adequate in all areas of California. This indicates a good producer understanding of where supplementation is needed. Copper deficiency was more widespread in the southern region when compared with further north. Zinc deficiency was seen ubiquitously statewide, with 36% of animals being deficient. Manganese has been largely ignored in California. This study is the first known documentation of manganese levels in the state. Sampling found 92% of cattle fell below critical manganese levels. However, further research to better define manganese critical levels is probably warranted. The status of other minerals is presented.

Timing Aminopyralid to Prevent Seed Production Controls Medusahead (Taeniatherum caput-medusae) and Increases Forage Grasses

Abstract Exotic annual grasses such as medusahead [Taeniatherum caput-medusae (L.) Nevski] and downy brome (Bromus tectorum L.) dominate millions of hectares of grasslands in the western United States. Applying picloram, aminopyralid, and other growth regulator herbicides at late growth stages reduces seed production of most exotic annual grasses. In this study, we applied aminopyralid to T. caput-medusae to determine how reducing seed production in the current growing season influenced cover in the subsequent growing season. At eight annual grassland sites, we applied aminopyralid at 55, 123, and 245 g ae ha-1 in spring just before T. caput-medusae heading. The two higher rates were also applied pre-emergence (PRE) in fall to allow comparisons with this previously tested timing. When applied in spring during the roughly 10-d period between the flag leaf and inflorescence first becoming visible, just 55 g ae ha-1 of aminopyralid greatly limited seed production and subsequently reduced T. caput-medusae cover to nearly zero. Fall aminopyralid applications were less effective against T. caput-medusae, even at a rate of 245 g ae ha-1. The growing season of application, fall treatments, but not spring treatments, sometimes reduced cover of desirable winter annual forage grasses. The growing season after application, both spring and fall treatments tended to increase forage grasses, though spring treatments generally caused larger increases. Compared with other herbicide treatment options, preheading aminopyralid treatments are a relatively inexpensive, effective approach for controlling T. caput-medusae and increasing forage production.

Targeted Grazing Impacts on Invasive and Native Plant Abundance Change with Grazing Duration and Stocking Density

ABSTRACT The science underpinning targeted grazing has been advancing for decades, supporting a major paradigm shift concerning the role of grazing in addressing critical natural resource management challenges across the globe. A next step for expanding adoption is to understand how conservation benefits derived from this practice may change depending on howthe components of a targeted grazing strategy change. Using two studies on California annual rangeland, onewith heifers and one with ewes, we evaluated how two stocking attributes that underpin a targeted grazing plan, animal density and grazing duration, influence the ability of livestock to reduce the abundance of the invasive annual grass medusahead (Taeniatherum caput-medusae [L.] Nevski) and increase the abundance of native plants. Across studies, conservation benefits tended to be higher (lower invasive plant abundance and greater native plant abundance) under higher stocking density and shorter stocking duration, but we also found evidence that stocking density could be relaxed in some situations, allowing some conservation benefits to be achieved by grazing fewer animals over a longer duration. For California annual rangelands where most vegetation growth occurs over a period of a few short weeks, the potential to achieve similar conservation benefits by extending grazing duration and using fewer animals represents a major opportunity to apply targeted grazing over larger areas in one season with a set number of grazing animals. These initial findings provide justification formore extensive research in how changes in targeted grazing strategies may alter conservation benefits from grazing. Such insight is essential for understanding the range of cost-benefit trade-offs thatmay occur with this practice.

Longevity of a Controlled Burn’s Impacts on Species Composition and Biomass in Northern California Annual Rangeland During Drought

ABSTRACT Controlled burning timed in early summer can dramatically change the species composition of annual rangeland the following season. Although this has been well documented, the longevity of these shifts has not. Presented is a case study of a single 200-ha burn to begin to understand how long plant communities and biomass production remain diverged between burned and unburned annual rangeland. Species composition and biomass production were monitored before and for 3 yr after burning. Burning drastically reduced medusahead (Taeniatherum caputmedusae; P < 0.01) the following year from 69% in the control to 4% cover in the area burned. In the same year, filaree (Erodium spp.; P < 0.01) filled in the area left vacant, subsequently lessening production (P < 0.01) in the burn area by over half that of the control. No difference existed in the occurrence of native wildflower species due to fire. Three consecutive drought years following the burn shifted the control from medusahead dominance to filaree in a linear fashion. At the same time, in the burned area medusahead cover increased fourfold between 1 and 3 yr after the burn. By 3 yr post burning, the area had 4% more medusahead cover than the control and was equal in filaree, rose clover (Trifolium hirtum), and soft brome (Bromus hordeaceus) cover. Our results suggest that a controlled burn followed by drought can cause the divergence in species composition and production to become void in as little as 3 yr after a well-timed burn in a low-elevation annual rangeland system.

Broadleaf weed control in irrigated pasture containing Trifolium repens

Abstract. Increasing lease and purchase costs for irrigated pasture are encouraging producers to use herbicides to control broadleaf weeds and maximise forage production on their current land base, as opposed to seeking out additional pastureland. There are two challenges to using herbicides to control broadleaf weeds in irrigated pasture. One challenge is that producers often encounter weed species for which herbicide information is limited or non-existent. Another challenge is that broadleaf herbicides tend to damage desirable legumes. We evaluated the efficacy of several broadleaf herbicide options for Symphyotrichum divaricatum, a species not previously the subject of research in irrigated pasture. Additionally, we monitored herbicide impacts on desirable legumes, principally Trifolium repens. We also evaluated control of Convolvulus arvensis and Plantago lanceolata, subjects of considerable herbicide research. Our goal was to identify herbicide options that controlled all three weeds while causing the least damage to legumes. Several rates and combinations of dicamba, diflufenzopyr, triclopyr, MCPA, and 2,4-D provided statistically indistinguishable control of C. arvensis and P. lanceolata, with point estimates suggesting 66–88% control in 2011 and 43–86% control in 2012. 2,4-D + triclopyr appeared to provide the best control of P. lanceolata and C. arvensis, with point estimates for high rates indicating nearly 100% control in both years. However, this combination was particularly damaging to legumes. Based on these findings, we recommend 2,4-D + triclopyr where desirable legumes are absent. Where desirable legumes are present, we recommend 2,4-D alone. Whereas 2,4-D alone appeared not to perform as well as 2,4-D + triclopyr at controlling S. divaricatum in 2012, it was less damaging to desirable legumes.