Barb goatgrass has a higher rating due to its more limited distribution and, therefore, greater opportunity for containment than medusahead. Both of these species commonly occur with other exotic annual grasses . As annual grasses, barb goatgrass and medusahead produce seed at the end of the growing season for subsequent germination in the fall. Inhibiting this seed production is crucial to suppressing or controlling both weeds. Unfortunately, barb goatgrass and medusahead are prolific seed producers, making management to reduce their abundance possible but eradication difficult and unlikely. Barb goatgrass compounds this problem because in addition to producing seed for the following season, it also produces a dormant set of seed that will not germinate until the second growing season after seed production, making 2 years of control necessary to reduce infestations. For these reasons, grazing has not yet proven to be a fully successful strategy for depleting stands of barb goatgrass. Mowing prior to seed maturity may be a better mechanism to control barb goatgrass. Fortunately, medusahead populations can be drastically reduced with a single event that suppresses seed production, lending it to both grazing and mowing treatment methods. Both of these methods require appropriate timing so that the mechanism matches the biological susceptibility of the plant for successful management. The timing of growth events, including major biological changes in plant growth and development through the season, is referred to as phenology. As applied to managing invasive annual grasses, the important events to consider include germination, vertical grow rack vegetative growth phases, and a series of reproductive growth phases that end in the production of viable seed.

As barb goatgrass and medusahead develop and change visually, other changes are less apparent, though important to consider, related to the nutritional quality for livestock grazing, ability of the individual plant to recover from defoliation , and the ability of the seed to continue to develop and later germinate after it is detached from the plant. While these changes are roughly predictable, variation from year to year, across regions, and even within pastures occurs due tovariation in weather, climate, landscape, presence of grazing, soil differences, and genetics. This means that predicting the timing for control can be somewhat imprecise, making the use of phenology observations imperative to optimize control treatments. University of California research conducted over multiple years describes how observations of plant growth stage can help to optimally time grazing and mowing treatments.The stages in table 1 provide a framework to describe how both of these species progress and change in their physical characteristics over the course of the growing season. The 12 stages are broken into vegetative stages V1 to V3, reproductive stages R4 to R9, a mature stage M10, a summer dry stage D11, and dead residual in the subsequent growing season at stage L12. Defining these stages helps to optimize the timing of grazing and mowing control treatments by defining the windows of susceptibility.During the first two vegetative stages the plants are very small and inconspicuous. They are often unnoticed when viewed on a landscape level and provide very little forage for grazing. When plants are grazed during these stages they will readily recover with new flowering stems; thus, little to no control is achieved. In order to impact plants heavily enough to prevent further reproductive stages from progressing, targeted grazing of the infested areas should begin during the late vegetative stage 3 or boot stage . Plants are affected by grazing from stage V3 until the reproductive stage 4 , when awns fully emerge, and neither grass species is palatable to grazing animals thereafter .

Crude protein of the vegetative grasses drops significantly from approximately 10 to 11 percent at the V3 stage to 7 to 8 percent at the R4 stage in the R8 stage , the seed is able to continue to develop and become viable if spikes detach from the plant. This can be visually approximated as the point that plant leaves and stem are turning brown, but the seeds and seed head are still green. The plant is fully mature once shades of red, brown, and green are apparent on the seed head . The window for treatment is much longer for mowing than grazing since palatability is not an issue.To better understand the timing of phenology of these two grasses in California, UC researchers measured the proportion of barb goatgrass and medusahead at various times through the growing season. Included were 18 locations in 11 counties from Shasta to Monterey at elevations from 80 to 990 feet above sea level during the growing season from 2006 to 2010. Whereas medusahead was present at all sites, barb goatgrass was present in samples taken from Tehama County to Yolo County. The limited range of sample locations for barb goatgrass reflected the more restricted range of this species compared with medusahead .Medusahead was sampled over a larger geographic range than barb goatgrass, and we therefore expected and observed more variability in the timing of phenology of medusahead relative to barb goatgrass. Medusahead became susceptible to grazing treatments from early or mid-April to early or mid-May, depending on the site and year. The transition from grazing susceptibility to only mowing susceptibility reliably occurred in early May and was usually complete in mid-May. Medusahead tends to enter the stage of maturity that is too late for effective mowing treatment between the last week of May and the first week of June. Some cooler locations in the Central Coastal valleys can be about a week later. In addition, there seem to be some locations with warmer winter temperatures and less moisture overall where this transition to maturity occurs much earlier, such as early May. Select sites in Glenn, San Joaquin, and Shasta Counties were consistently 2 to 4 weeks earlier than other sites. This may be due to a number of factors, including locally warmer spring temperatures. Barb goatgrass became susceptible to grazing treatments from mid-March to mid-April; however, grazing is not recommended at this time due to the existence of a dormant seed bank and less complete control compared with mowing, making this approach challenging. In 2007, barb goatgrass began developing notably later; 2007 was the only year when barb goatgrass collections made in late March and early April were not yet susceptible to grazing. During other years, the first collections made in early April were already susceptible to livestock grazing. The transition from susceptibility of grazing to only mowing reliably occurred in early May and was complete by mid-May. Generally, at all sites, barb goatgrass entered the stage of maturity that is too late for effective mowing treatment around June 1, with a variance of about 5 days. One year seemed to have more variability, with several sites maturing earlier and others sites later than other years. At the pasture scale, some individuals and patches of medusahead will mature more quickly than others due to variation in soils, slope, and aspect. In more-uniform pastures, most individual and patches of plants may be well synchronized, while in morevariable pastures there may be a greater range of stages at any given time in the spring. This can lead to patchy areas, with some grasses that are too early for treatment success and others that are too late for treatment success. Variable effects within pastures are amplified when they are not grazed. In these cases, managers will need to keep in mind that grazing should be considered a long-term approach that will not be fully successful every year .While the start of susceptibility varies substantially, commercial vertical hydroponic systems ranging from late March to early May, the duration of susceptibility for both barb goatgrass and medusahead tends to vary across its range and from year to year, but in somewhat predictable patterns.

The period of susceptibility of medusahead to targeted grazing is 2 to 3 weeks, while susceptibility to mowing of both species is about 5 weeks. The length of these periods varies by year, location, precipitation, and soils . Cooler spring seasons tend to lengthen the period of susceptibility relative to drier, warmer sites and years. Livestock stocked at moderate or light stocking rates will avoid medusahead and goatgrass particularly as plants transition fromV3 to R4. To overcome this aversion, heavy stocking rates that far exceed rates considered normal for annual rangelands are required to encourage enough consumption to impact seed production. For grazing to be successful, plants must be impacted enough to prevent the onset of seed set. This is possible because these two species tend to mature so late in the season that soil moisture is not present in adequate amounts for plant recovery , although this is not the case every year. The rate is determined by the forage biomass present, but it often exceeds 1 to 2 animal units per acre during the critical V3 and early R4 stages. This high rate is necessary because of the short window and amount of forage that needs to be removed. The objective is to consume forage biomass to, or even slightly below, 500 pounds per acre . This makes treatment site-specific within most ranches because of the difficulty of fencing, watering, and providing enough cattle to impact an area, as well as the increased management time. The short period of susceptibility for successfully implementing a grazing treatment can be overcome with mowing treatments. When implemented correctly, mowing is more likely to be a successful treatment than grazing because the timing will almost, but not always, prevent subsequent seed production. However, mowing faces other challenges, including the inability to cover steep terrain, rocks that damage the mower, and fire potential, which are very common scenarios on California rangelands. It is important to ensure that these treatments are applied as effectively as possible to get the most benefit out of them. By understanding the phenology of barb goatgrass and medusahead, these treatments can be better planned so that the timing and intensity of treatment corresponds to when they will most effectively reduce the abundance of these noxious annual grasses in the future.Grazing and mowing are two of many successfully tested weed control methods that can be used in combination with other methods for medusahead and barb goatgrass control. Using multiple methods is highly suggested for barb goatgrass areas. Ultimately, treatment decisions are site and management specific. Specifics on the effectiveness and implementation of the various other treatment options, such as burning and herbicide application, are available from sources such as Davy et al. 2008, DiTomaso and Kyser 2013, and Kyser et al. 2014. In addition, articles by Aigner and Woerly and James et al. have also assessed the effectiveness of different treatment tools on barb goatgrass and medusahead, respectively.Crops that grow vigorously can often outcompete weeds. Weeds grow best where competition is sparse; for instance, between rows or in gaps in a crop stand. Crops that are well adapted to their planted areas are often better competitors since they will tend to occupy a site rapidly. If you increase the density of the crop by decreasing the in-row spacing or by reducing the space between rows you will improve the crop’s competitiveness. A close-planted crop will close the canopy more rapidly, reducing the weeds’ ability to compete. Some crops compete effectively with weeds if given an early competitive advantage, while others never establish a competitive canopy. The use of transplants give the crop an advantage over the weeds because transplants enter the field larger and more developed that the weeds. With help from subsequent cultivation or hand weeding operations, a transplanted crop can develop a full canopy and crowd out weeds.Practices that reduce the production of weed seed also reduce weed pressure and can help keep weeding costs down over time. In an ideal situation, no weed would be allowed to go to seed. Any that do go to seed can aggravate weed problems for many years to come. As an example, common purslane seed has been shown to remain viable for over 20 years in the soil, and black mustard seed survives for over 40 years. The longevity of weed seed, together with the large numbers of seed produced by individual plants , can lead to the long-term build-up of enormous seed banks in the soil. If you make it a policy to remove weeds prior to seed production, you can reduce weed pressure in subsequent seasons.