Biology and Nymph Host Range ofAnchocoema bidentataandAstroma saltense(Orthoptera: Proscopiidae), Potential Biocontrol Agents for Creosotebush,Larrea tridentata(Zygophyllaceae) in the U.S.A.

Abstract

Two stick-like acridids (Orthoptera: Proscopiidae) from Argentina, Anchocoema bidentata Mello-Leitao and Astroma saltense Mello-Leitao, were evaluated as potential biological control agents of creosote bush (Larrea tridentata (DC.) Coville) in the southwestern United States. Their biology, behavior and geographic distribution of those species were studied. The host plant ranges for both insects were established through nymph feeding preference and development tests in the laboratory and in the field. A total of 33 species of plants belonging to 13 families were tested. Anchocoema bidentata and A. saltense are mimetic species, having as many as three generations a year, and exhibit strong sexual dimorphism; females are larger and less mobile than males. In both species, females laid egg masses in the soil. First instars appeared in the field at the end of the spring, the second generation at mid-summer, and a third at the end of the summer. Adults of A. bidentata and A. saltense appeared in the field at the beginning of the spring. The laboratory multiple-choice feeding test showed that A. bidentata preferred Larrea divaricata Cav., whereas A. saltense preferred L. divaricata and L. cuneifolia Cav. In the nymph development test (no choice), A. bidentata was able to complete its development only on L. divaricata and L. cuneifolia, while Astroma saltense completed its development on six plant species: L divaricata, L. cuneifolia, Bulnesia retama (Gillies ex Hooker et Arnott), B. schickendantzi Hieron (all Zygophyllaceae), Zuccagnia punctata Cav., and Prosopis torquata (Cav. Ap. Lag.) (both Fabaseae). We concluded that A. bidentata could be a biocontrol agent for L. tridentata because the first instar can complete its development only on Larrea spp. Regarding A. saltense, this species showed a wide host range and should not be considered as a biological control agent of L. tridentata.