Abundance of Grasshoppers in Relation to Rangeland Renovation Practices Item Type text; Article Authors Hewitt, G. B.; Rees, N. E. Citation Hewitt, G. B., & Rees, N. E. (1974). Abundance of grasshoppers in relation to rangeland renovation practices. Journal of Range Management, 27(2), 156-160. DOI 10.2307/3896756 Publisher Society for Range Management Journal Journal of Range Management Rights Copyright © Society for Range Management. Download date 30/09/2021 21:08:14 Item License http://rightsstatements.org/vocab/InC/1.0/ Version Final published version Link to Item http://hdl.handle.net/10150/647071 Abundance of Grasshoppers in Relation to Rangeland Renovation Practices G. B. HEWITT AND N. E. REES Highlight: This study was conducted during a 3-year period, Part 1. Chemical and Mechanical Methods 1969-1971, in northcentral Montana to determine the effect of Controlling Sagebrush of the rangeland renovation practices of scalping, interseeding, contour furrowing, and spraying sagebrush with 2,4-D and the This study was conducted in Petroleum County near resulting vegetational changes on grasshopper (Acrididae: Winnett, Montana, in cooperation with the Montana Fish and Orthoptera) species and abundance. Spraying for control of Game Department and the Bureau of Land Management, U. S. sagebrush with 2 lb of 2,4-D ester in 6 gal H,O/acre only Department of the Interior. Methods of controlling sagebrush slightly reduced grasshopper abundance during the first 3 post- included use of chemicals, furrowing, and scalping and inter- spray years. However, contour furrowing, scalping, and inter- seeding . seeding in general adversely affected the habitat of most grass- hopper species, probably because of changes in the abundance Procedures of preferred food plants. The influence of parasites, predators, Although four study areas were established by the agencies and pathogens on abundance appeared to be slight. that initiated the study, only two (Winnett and King) were used in studying grasshoppers. Within these two areas, the plots used for the study of insects (treated and untreated) The production of livestock, the largest source of income in were located on vegetational transects laid out on each of the Montana, depends on the grazing of 70% of the land area of major soil types present. the state. Montana has 54 million acres of rangeland and 11 YZ Measurements of vegetation were made by Montana Fish million acres of grazeable timberland (Jackson, 1970), but and Game personnel during the summers of 1967, 1969, and approximately 34l+$million acres are vegetated by some species 197 1. The canopy coverage (cm* ) was multiplied by the mean of sagebrush (Beetle, 1960). During the last 20 years, the height (cm) to obtain a reasonable approximation of the removal of sagebrush has been a primary method of increasing volume or “cover index” occupied by each plant species. Thus vegetation on treated and untreated portions of both study the amount of forage (Pechanec et al., 1965). Another method areas could be compared by summing the cover indexes of of increasing forage production is scalping, in which 10 to each species from all plots exposed to a given treatment to 25-inch-wide strips of native vegetation to a depth of 4 inches obtain a total cover index (TCI). The amount of change per are removed, laid over on adjacent sod, and strips between left species (assumed to result from treatment) was then calculated undisturbed. When the scalped strips are seeded, the procedure as the “corrected vegetational change” or CVC (adapted after is termed interseeding (Hervey, 1960). However, little atten- Anderson, 196 1) as follows: tion has been given to the effects on nontarget organisms cvc = resulting from these renovation practices. Two separate studies TCI Treatment 197 1 (Parts 1 and 2) were conducted with the main objective to X TCI Untreated 1967 -TCI Untreated 1971 TCI Treatment 1967 determine the abundance of grasshoppers (Acrididae: Orthop- > tera) and the fluctuations in species resulting from vegeta- Mechanical treatments were applied in the autumn of 1967; tional changes due to treatment. The influence of parasites, chemical treatments were applied June, 1968. Sampling plots, predators, and disease organisms of grasshoppers was also of approximately 3 acres each, were established in both treated and adjacent untreated areas the spring of 1969 as investigated. follows: Winnett Study Area Authors are research entomologist and entomologist, Grasshopper 1. Aerial application of 2 lb of 2,4-D ester/acre to 480 Laboratory, Agricultural Research Service, U.S. Department of Agricul- ture, Bozeman, Montana. acres for total kill of big sagebrush: six plots. The authors wish to thank Elaine Oma, who examined the grass- hoppers for pathogens, and Wayne Burleson for field assistance, both of King Study Area the Grasshopper Laboratory, Agr. Res. Serv., U.S. Dep. Agr., Bozeman, Mont. The cooperation of Thomas Mussehl, Duane Pyrah, and Henry 1. Aerial application of 2 lb of 2,4-D ester/acre to 240 Jorgensen of the Montana Fish and Game Department is greatly appre- acres for total kill of big sagebrush: five plots. ciated. Special thanks go to the owners of the Cornwell ranch, the Nyquist Ranch, and the Veseth Ranch for providing three of the study 2. Contour furrowing of 321 acres: six plots. areas. The cooperative efforts of the Montana Fish and Game Depart- 3. Interseeding of 190 acres (scalped strips were 18 inches ment, Bureau of Land Management, U.S. Department of the Interior, wide and 4 inches deep and interseeded with a mixture of 1 lb and numerous land owners and research workers made the study possible. of western wheatgrass and 2 lb of green needlegrass per acre): Manuscript received March 15, 1973. five plots. 156 JOURNAL OF RANGE MANAGEMENT 27(2), March 1974 o - -. -Winnett Untreated 200 o- _ - -Winnett Untreated o- Winnett 2,4-D Treated o---Winnett 2,4-D Treated D - - - -King 2,4-D Treated .30 180 A- - - -King Untreated A- King Untreated A-King 2,4-D Treated .25 A-A .20 N ‘CI $ .I5 B f .lO ul d y .05 % . I a . 1 . I May- July Aug.- May July Aug.- May- July Aug.- May- July Aug.- May- July Aug.- May- July Aug.- June Sept. June Sept. June Sept. June Sept. June Sept. June Sept. 1969 1970 1971 1969 1970 1971 Fig. 1. Effect of 2,4-D treatment in 1968 on numbers of grasshoppers Fig. 2. Effect of 2,4-D treatment in I968 on numbers of grasshoppers collected by sweeping. per square yard. The distance between treated and untreated plots ranged Putnam (1949) found that treating plots of wheat stubble from approximately 200 to 2,000 yards. Movement of with 2,4-D did not reduce populations of the migratory grasshoppers was probably negligible, since populations were grasshopper, Melanoplus sanguinipes (= mexicanus) (F.): the less than l/yard2 during the study. average population on treated always exceeded that on Each plot was sampled three times a year in each of the 3 untreated plots. However, Bird et al. (1966), thought that the years 1969- 1971: in May or June to sample species that treatment of weedy roadsides with herbicides might minimize overwinter as nymphs, in July, and again in August or increases in populations of roadside grasshoppers during September to sample species that overwinter in the egg stage. periods of drought. In our opinion, any changes in populations The numbers and species composition of grasshoppers were of grasshoppers due to herbicides probably depends on the measured in two ways: success of the treatment in controlling weeds and on the food 1. Density was determined by visually estimating the preferences of the species of grasshopper. number of grasshoppers in a square-yard area while walking in In the 3 years of this study, 42 grasshopper species were a straight line across a plot. Twenty such counts were made in each plot at each sampling time. collected from the two study areas; however, only 39 were 2. Grasshoppers were collected by sweeping with a net for found on the chemically treated plots. Only 16 species were 10 minutes on each plot. They were then taken to the labora- collected in sufficient numbers for comparison of possible tory where the number and species of parasites emerging could treatment effects. These are listed in Table 1 with their be determined and the relative abundance of the different percentage change. species could be assessed. Also, three times in 1969 and once The migratory grasshopper was the most abundant species in 1970 grasshoppers collected in the field and frozen with dry ice were examined in the laboratory for disease organisms. collected from the Winnett area and Psolessa delicatula delicatula was the most abundant species on the King area. Results and Discussion Fewer P. d. delicatula were collected on treated plots of the King area all 3 years, but on the Winnett area no real Chemical treatment of big sagebrush on Winnett and King difference was apparent. The migratory grasshopper was about areas. equally abundant on treated and untreated plots on both The abundance of grasshoppers determined from sweeping areas. Arphia conspersa, Arphia pseudonietana, and Opeia is shown in Figure 1. During the 3 years, 5 10 were collected in obscura were more abundant on treated plots on both areas, treated plots in the Winnett area vs 656 in untreated plots, a but Trimerotropis campestris was less abundant. The other 22% reduction due to treatment. In the King area, the total species listed in Table 1 were not consistent in response to was 45 1 vs 5 17, a 13% reduction due to treatment. The treatment between areas. numbers collected during May-June in treated plots were Changes in vegetation could only be related to changes in always less than the numbers collected in untreated plots at abundance of grasshoppers in a general way.