Browsing Journal of Range Management, Volume 35, Number 2 (March 1982) by Subjects
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Destructive and Potentially Destructive Insects of Snakeweed in Western Texas and Eastern New Mexico and a Dioristic Model of Their Biotic InteractionsThe relationships of the principal destructive and potentially destructive insects associated with Xanthocephalum microcephalum (DC) Shinners (threadleaf snakeweed) and Xanthocephalum sarothrae (Pursh) Shinners (broom snakeweed) have been identified and depicted with a dioristic model. Every region of the host plant is utilized by insects in one or more of the following feeding categories: defoliators, fluid feeders, borers, and gall-formers. Roots, stems, leaves, flowers, and fruit each have their own complement of insect associates. A system analysis reveals a complex picture of insect-host plant interactions as well as potential insect-insect interactions. The roles that these insects play in the natural biological control of threadleaf and broom snakeweed are poorly understood but the general information portrayed in the model of their interactions will help future workers to determine the most productive avenues of research.
Grass Response Following Thinning of Broom SnakeweedComplete removal of broom snakeweed resulted in perennial grass production 833% of that on untreated rangeland after one growing season, and 712% and 300% the second and third year, on a pasture heavily grazed and in poor range condition. On a moderately grazed pasture in good range condition, grass standing crop increased 42% the first year, 81% the second, and 25% the third compared to untreated rangeland. Perennial grass production on the heavily grazed pasture was far below that on the moderately grazed pasture at the start of the study (40 vs 454 kg/ha). After 3 years, with complete broom snakeweed removal and no grazing, perennial grass production was comparable on the pastures once heavily and moderately grazed (1014 vs 939 kg/ha, respectively).