Larval Insects Boring in the Roots of Perennial Broomweed (Gutierrezia Sp.) In West Texas
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Rangeweeds in the Southwestern United States present a serious problem to agriculture. The density of native weeds has increased dramatically due to a change in the range ecosystem from an area periodically grazed to one extensively grazed by domestic animals. Broomweed (Gutierrezia sp.) is a native plant which is toxic to cattle and competes with desirable grasses for water and nutrients. The purpose of this study was to determine the insects which infest the roots of broomweed in order to estimate the amount of competition an introduced biological control agent may encounter, as well as the amount of control exerted by natural populations of root boring larvae. Plants closely related to broomweed (family Compositae) were also sampled to determine the host-range of a moth larva (Sesiidae) reported on broomweed. Five borer species were found on broomweed. Members of the order Coleoptera included the families Buprestidae, Cerambycidae, Cleridae and Curculionidae. Lepidopterous larvae from the family Sesiidae were also encountered. The Sesiid moth larvae were not found on four additional composite species collected in the same area.