Host Specificity Tests of Gratiana graminea (Coleoptera: Chrysomelidae), A Potential Biological Control Agent of Tropical Soda Apple, Solanum viarum (Solanaceae)

J. Medal, N. Bustamante, M. Vitorino, L. Beal, W. Overholt, R. Diaz, J. Cuda


Multiple-choice and no-choice tests were conducted at the Department of Agriculture, Division of Plant Industry Quarantine facility in Gainesville, FL to determine the specificity of the Brazilian leaf-beetle Gratiana graminea Klug, a candidate for biological control of Solanum viarum, tropical soda apple. One hundred fifteen plant species in 32 families were included in the feeding-oviposition multiple-choice tests including the target weed and the 5 major cultivated Solanaceae Capsicum annuum L., Lycopersicon sculentum Mill., Nicotiana tabacum L., Solanum melongena L., and Solanum tuberosum L. Eight to 12 plant species, including always the main target weed, growing in 1-gallon pots were simultaneously exposed to 20 G. graminea adults (10 males and 10 females that most of the time had recently emerged from pupae) in an aluminum cage (60 × 60 × 60 cm). At the beginning of each test the insects were placed at the bottom center of each cage to allow them to orient by themselves to the tested plants. Plant species in each test were replicated 3–4 times (one replication of tested plants in each separate cage). Plants tested were exposed to G. graminea adults from 3–6 weeks. Observation of oviposition and feeding were made during almost all the weekdays. No-choice host specificity tests were conducted with G. graminea adults on potted plants in cages made of clear-plastic cylinders and with G. graminea larvae placed on cluster of leaves of each individual plant tested. Ten G. graminea adults were exposed to 29 plant species individually tested during 3 to 5 weeks, and 10 neonate larvae were exposed to 31 plant species. Plant species in each test were replicated 3–4 times. Results indicated that G. graminea fed and developed only on the target weed. The tests indicated that a host range expansion of G. graminea to any of the major cultivated Solanaceae species is highly unlikely. A petition for field release in Florida was submitted to the Technical Advisory Group for Biological Control Agents of Weeds (TAG) in Sep 2008.

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