Suppression of grasshoppers in the Great Plains through grazing management
AuthorOnsager, J. A.
twice-over grazing system
MetadataShow full item record
CitationOnsager, J. A. (2000). Suppression of grasshoppers in the Great Plains through grazing management. Journal of Range Management, 53(6), 592-602.
PublisherSociety for Range Management
JournalJournal of Range Management
AbstractIt was hypothesized that grazing management could mitigate grasshopper outbreaks on native rangeland in the northern Great Plains. Key practices would require deliberate variation in timing and intensity of grazing events, preservation of canopy during critical periods of grasshopper development, and reductions in areas of bare soil. The twice-over rotational grazing system appeared compatible with those requirements. Grasshopper population trends were monitored during 1993–1995 and 1997–1998 on commercial native rangeland under twice-over rotational grazing vs traditional season-long grazing. A ubiquitous pest grasshopper, Melanoplus sanguinipes (Fabricius), occurred at every sample site during each year in numbers sufficient to provide life history parameters for comparison between treatments. Under rotational grazing, the nymphs developed significantly slower and their stage-specific survival rates were significantly lower and less variable. Consequently, significantly fewer adults were produced signifi-cantly later in the season under rotational grazing.Seasonal presence of all grasshopper species combined averaged 3.3X higher under season-long grazing than under rotation-al grazing. Local outbreaks that generated 18 and 27 adult grasshoppers per m2 under season-long grazing in 1997 and 1998, respectively, did not occur under rotational grazing. The outbreaks consumed 91% and 168%, respectively, as much forage as had been allocated for livestock, as opposed to 10% and 23%, respectively, under rotational grazing. Of 9 important grasshopper species, none were significantly more abundant at rotational sites than at season-long sites. Three species that were primary contributors to outbreaks under season-long grazing remained innocuous under rotational grazing. It therefore appears that outbreak suppression through grazing management is feasible in the northern Great Plains.
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Some effects of a rotational grazing treatment on cattle grazing behaviorWalker, J. W.; Heitschmidt, R. K. (Society for Range Management, 1989-07-01)Research was conducted on the effects of rotational grazing (RG) compared to continuous grazing (CG) on the behavior of cattle grazing on rangelands. Different livestock densities in the RG treatments were created by varying the size of paddocks in a 465-ha, 16-paddock, cell designed RG treatment stocked at a rate of 3.6 ha/cow/yr. Paddock sizes of 30 and 10-ha were used to simulate RG with 14 (RG-14) and 42-paddocks (RG-42), respectively. The CG treatment consisted of a 248-ha pasture stocked at 5.9 ha/cow/yr. Data were collected using vibracorders, pedometers and observation to estimate time (min/day) spent: intense grazing, search grazing, trailing, or sleeping; distance walked (km/day), and individual animal space ( m2/animal) in grazing subherds. Total grazing time did not vary among grazing treatments, but the components of total grazing (i.e., intense and search grazing) did vary among treatments. Cattle in the RG-14 paddocks spent less time search grazing compared to the ones in the other treatments presumably because the rotational grazed paddocks were more uniform because of less mixing of live and dead forage. Search grazing was highest in the RG-42 paddocks which may be due to the high stock density in this treatment coupled with an attempt to maintain individual animal space. Grazing time tended to be longer the first day in a RG-14 paddock than the last. Time spent trailing and the distance walked increased as the frequency of rotation increased among the different treatments. Sleeping was similar among grazing treatments. Individual animal space within a grazing subherd decreased as the stock density increased because of the grazing treatment.