U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Pest Management Research: Sidney, MT
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                People

                    Staff Listing
                                    Careers


        


                    NPARL
                        Northern Plains Agricultural Research Laboratory
                                    Agricultural Systems Research Unit
                                    Grasshoppers: Their Biology, Identification and ManagementSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Plains Area Sidney, Montana Northern Plains Agricultural Research Laboratory Pest Management Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            Branson, David

                                                         - *Dave*item
                                            Haferkamp, Marshall
  Submitted to: Ecological Entomology
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 1/30/2014
                                    Publication  Date: 2/1/2014
                                    Publication URL: http://handle.nal.usda.gov/10113/58796Citation: Branson, D.H., Haferkamp, M.R. 2014. Insect herbivory and vertebrate grazing impact food limitation and grasshopper populations during a severe outbreak. Ecological Entomology. 39(1):371–381.Interpretive Summary: Grasshoppers are often the dominant herbivore in western U.S. grasslands. Grasshopper outbreaks also cause significant economic hardship for ranchers and can result in competition with livestock for rangeland plants. Grasshopper populations tend to increase with grazing intensity in the northern Great Plains, but our understanding of why specific outbreaks occur is still lacking. Little research has examined how the timing of livestock grazing might negatively impact grasshopper populations. An experiment was conducted at the USDA, ARS, Livestock and Range Research Lab in eastern Montana, during a naturally occurring grasshopper outbreak where densities of grasshoppers reached 130 per m2.  We manipulated grasshopper densities and sheep grazing inside cages to examine their relative importance on grasshopper populations. Both sheep herbivory and grasshopper herbivory led to food limitation and reduced future year grasshopper populations, but the larger effects were from grasshoppers. Grasshopper populations crashed over six fold in the year following the experiment, due to low levels of reproduction. The results indicate that grasshoppers can have stronger effects than livestock grazing in determining future grasshopper populations during outbreak periods, although livestock grazing can have important effects at lower grasshopper densities. The results can be used to better predict the onset and decline of future grasshopper outbreaks. These results indicate that severe outbreaks can rapidly subside when food is limiting, potentially reducing the economic justification for control programs which have non-target effects.
                                Technical Abstract: Interspecific competition between distantly related herbivores, as well as between large vertebrate herbivores and phytophagous insects, has received little attention. Livestock grazing is the dominant land use in western North American grasslands, where phytophagous insects can be the dominant herbivore. Large scale studies have examined interactions between livestock grazing and grasshoppers, but manipulations of grazing and grasshopper densities to clearly examine competition are lacking. In a novel design, we manipulated grasshopper population densities and the timing and frequency of sheep grazing inside 10m2 caged mesocosms to examine their impact on grasshopper population dynamics and vegetation. We utilized a replicated, factorial experimental design during a naturally occurring grasshopper outbreak. Field densities of grasshoppers reached 130 per m2 in 2000. Grasshoppers removed much of the available vegetation biomass during the experiment, as green grass biomass was eight times higher in vegetation control cages than in field density cages. As a result of high densities, exploitative competition from grasshopper herbivory was dominant in all treatments. Proportional survival and number of grasshoppers surviving were lower in field relative to reduced density cages. Higher grasshopper population densities and late season and multiple grazing both accelerated the population decline resulting from food limitation. Strong density dependence was evident in reproduction, as fewer grasshoppers hatched in field density than in reduced density treatments in 2001. Few detailed experiments have been conducted during grasshopper outbreaks. The results indicate that phytophagous insect herbivory can have stronger effects than livestock grazing on population dynamics during an outbreak, but livestock grazing and grasshopper herbivory interacted at the lower density. Additional research examining interactions between livestock grazing and grasshoppers is needed at lower grasshopper densities.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov