UC IPM Online UC ANR home page UC IPM home page

UC IPM Home

SKIP navigation

 

Research and IPM

Grants Programs: Projects Database

Project description

Grazing management practices for long-term yellow starthistle control in established perennial grasslands. (00CC023)
Program UC IPM competitive research grants program
Principal
investigators
S.B. Orloff, Cooperative Extension, Siskiyou County
D. Drake, Cooperative Extension, Siskiyou County
K. Tate, Agronomy and Range Science, UC Davis
Host/habitat Rangeland
Pest Yellow Starthistle Centaurea solstitialis; Wheatgrass
Discipline Weed Science
Review
panel
Cultural Controls
Start year (duration)  2000 (Two Years)
Objectives Determine the effects of spring, early summer and continuous grazing strategies on pubescent wheatgrass and yellow starthistle populations.

Determine the effects of different grazing regimes on soil moisture use patterns by pubescent wheatgrass, yellow starthistle, and annual grass dominated rangeland.

Determine the population dynamics of yellow starthistle following previous clopyralid applications of 1, 2, or 3 years in wheatgrass or annual grass dominated rangeland.

Measure and contrast total forage production and quality under simulated spring, early summer and continuous grazing management strategies.

Economically evaluate all grazing strategies to determine the most cost-effective method for maintaining a perennial grass stand and preventing yellow starthistle invasion.

Final report Previous research has determined the proper grazing strategies for yellow starthistle management in annual grasslands. However, the effectiveness of those strategies has not been evaluated in reseeded perennial grass systems where timing of grazing is critical for maintaining productive grass stands. We examined the effects of simulated grazing (clipping) in a high intensity, short duration fashion at three growth stages of yellow starthistle (rosette, bolting, and early flower) in mixed stands of yellow starthistle and pubescent wheatgrass. These clipping timings corresponded to the vegetative, early flowering, and seed set stages of pubescent wheatgrass. In 2000, yellow starthistle vegetative cover and biomass production were strongly affected by the timing of clipping and the previous clopyralid treatments used for wheatgrass establishment in the system. When grazed during the rosette stage, yellow starthistle cover was significantly increased compared to the other grazing treatments.

In 2001, a severe drought resulted in complete yellow starthistle mortality in the experiment. However, pubescent wheatgrass, a drought-tolerant perennial, produced 900 kg/ha more dry matter than the downy brome that replaced yellow starthistle. Forage dry matter was higher at the later two grazing stages than the early stage. Forage quality was not different between range types (annual grass or perennial grass) and significantly decreased in both types over the growing season. Pubescent wheatgrass fall recovery was not significantly different among clipping treatments and wheatgrass recovery one year after clipping was also not significantly different between treatments.

These results suggest that pubescent wheatgrass is initially robust to clipping and provides the highest level of yellow starthistle suppression when clipped later in the season. The yellow starthistle suppression it provides is likely a more important factor than the reduction in forage quality with late season clipping. These results stress the need for large scale grazing research in perennial grass revegetated areas given the increased promotion of native grass restoration.

Second-year
progress
Previous research has determined the proper grazing strategies for yellow starthistle management in annual grasslands. However, the effectiveness of those strategies has not been evaluated in reseeded perennial grass systems where timing of grazing is critical for maintaining productive grass stands. We examined the effects of simulated grazing in a high intensity, short duration fashion at three growth stages of yellow starthistle (rosette, bolting, and early flower) in mixed stands of yellow starthistle and pubescent wheatgrass. These grazing timings corresponded to the vegetative, early flowering, and seed set stages of pubescent wheatgrass. In 2000, yellow starthistle vegetative cover and biomass production were strongly affected by the timing of grazing and the previous clopyralid treatments used for wheatgrass establishment in the system. When grazed during the rosette stage, yellow starthistle cover was significantly increased compared to the other grazing treatments.

In 2001, a severe drought resulted in complete yellow starthistle mortality in the experiment. However, pubescent wheatgrass, a drought tolerant perennial, produced 900 kg/ha more dry matter than the downy brome that replaced yellow starthistle. Forage dry matter was higher at the later two grazing stages than the early stage. Forage quality was not different between range types (annual grass or perennial grass) and significantly decreased in both types over the growing season. Pubescent wheatgrass fall recovery was not significantly different among grazing treatments and wheatgrass recovery one year after grazing in 2000 was also not significantly different between treatments.

The results from 2000 and 2001 suggest that pubescent wheatgrass is initially robust to grazing and provides the highest level of yellow starthistle suppression when grazed later in the season. The yellow starthistle suppression it provides is likely a more important factor than the reduction in forage quality with late season grazing. However, the long-term sustainability of pubescent wheatgrass grazed during its reproductive stages is still uncertain.

Top of page


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright 2014 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   web template revised: August 27, 2014 Contact webmaster.