Biology and host range of Omolabus piceus, a weevil rejected for biological control for Schinus terebinthifolius in the USA

Surveys for biological control agents of the invasive weed Schinus terebinthifolius (Anacardiaceae) discovered two Omolabus weevils (Coleoptera: Attelabidae) feeding on the plant in its native range. Molecular and morphological analysis indicated that one of these species consistently fed on the target weed and the other species fed more broadly. Aspects of the biology and host range of the more specific species, Omolabus piceus (Germar) were examined to determine its suitability as a biological control agent of S. terebinthifolius in the USA. Adults feed on newly formed leaves, and eggs, larvae and pupae develop in curled fragments of leaves, called nidi. Larvae consumed an average of 11.3 (±0.4) mg throughout their development which required 15.1 (±0.2) days. An average of 31.6 (±2.7) eggs were laid per female during their 23.8 (±2.2) day lifetime, after a 3.4 (±1.0) day preoviposition period. In no-choice tests, O. piceus adults fed and oviposited on all tested native North American, Caribbean and agricultural Anacardiaceae species except for M. indica. The field host-range of O. piceus, as determined by samples of host use in the native range, included three Schinus, two Lithrea and one Anacardium species. Therefore, we do not recommend O. piceus for biological control of S. terebinthifolius in the USA. However, the utilization of this species in other infested areas such as Hawaií and Australia should be considered.