RESOLVING AMBIGUOUS RESULTS OF HOST-SPECIFICITY TESTS - THE CASE OF 2LEPTINOTARSA SPECIES (COLEOPTERA, CHRYSOMELIDAE) FOR BIOLOGICAL-CONTROL OF SOLANUM-ELAEAGNIFOLIUM CAVANILLES (SOLANACEAE) IN SOUTH-AFRICA

Two leaf-feeding chrysomelids from North America, Leptinotarsa, sa tex ana (Schaeffer) and Leptinotarsa defecta (Stal), are promising candida tes for the biological control of Solanum elaegnifolium Cavanilles (So lanaceae) in South Africa. Permission for release was delayed because the beetles fed on cultivated eggplant (Solanum melongena Linnaeus) un der cage conditions. After considerable deliberation and further inves tigation, it was concluded that the results of the cage tests had been overemphasized. The beetles were cleared for release in South Africa on the following grounds: (i) neither Leptinotarsa species attacks egg plant in their native North American habitats; (ii) in South Africa, m any insect herbivores of Solanaceae feed on eggplant in cultivation bu t cause minor damage relative to cosmopolitan polyphagous pests; (iii) as with L. texana and L. defecta, Conchyloctenia tigrina Olivier, a S outh African chrysomelid that also occurs on eggplant in cultivation, fed on eggplant in indoor cages, but preferred its natural Solanum hos ts in large outdoor cages; (iv) eggplant cultivation methods include c rop rotation and severe pesticide regimes, which should exclude Leptin otarsa along with the other insects. This evidence showed that L. texa na and L. defecta are, at the most, only a minor threat to eggplant cu ltivation in South Africa, and the beetles were cleared for release in South Africa during 1992.