Damage potential of Hesperotettix viridis (Orthoptera: Acrididae) on a rangeland weed, Gutierrezia sarothrae

• Published in: Environmental entomology Vol. 24; no. 5; pp. 1315 - 1321
• Main Authors: Thompson, D.C, McDaniel, K.C, Torell, L.A, Richman, D.B
• Format: Journal Article
• Language: English
• Published: 1995
• Subjects: Acrididae; defoliation; density; density dependence; Gutierrezia sarothrae; insect defoliation; mortality; population density; rangelands; size; New Mexico
• ISSN: 0046-225X; 1938-2936
• DOI: 10.1093/ee/24.5.1315

The vulnerability of broom snakeweed, Gutierrezia sarothrae (Pursh) Britton & Rusby, to herbivory by the grasshopper, Hesperotettix viridis (Thomas), was quantified by placing various densities of grasshoppers on individual caged plants. Field experiments were conducted in the summers of 1989 and 1990 at 2 shortgrass prairie locations in eastern New Mexico. In general, grasshoppers removed most photosynthetic tissue from small plants within 7 d at an initial density of 16 grasshoppers per plant, and in approximately 14 d with an initial density of 8 per plant. Grasshopper densities of 2 per plant rarely consumed all photosynthetic tissue, irrespective of plant size, during caged experiments. Although not consistent over sites and years, grasshopper feeding reduced plant volume and the number of photosynthetic stems from small and medium plants at densities of 8 and 16 grasshoppers per plant. Grasshopper defoliation caused 8, 23, 34, and 47% G. sarothrae mortality at densities of 2, 4, 8, and 16 grasshoppers per plant, respectively. Grasshopper feeding pressure was significantly correlated with observed defoliation and suggests feeding by >4 H. viridis per plant results in a significant decrease in aboveground photosynthetic biomass.