Insects for the biological control of Chromolaena odorata: surveys in the northern Caribbean and efforts undertaken in South Africa

摘要

With recent evidence indicating that the southern African biotype of Chromolaena odorata has a northern Caribbean origin, surveys of insects on chromolaena were conducted in Cuba and Jamaica. These revealed a depauperate entomofauna with no 'new' agents. Compatible biotypes of insects from other countries (e.g. Venezuela) are thus still needed to supplement promising agents from the northern Caribbean. Diptera, Lcpidoptera and eriophyid mites were the main groups of arthropods collected on C. odoratain Cuba and Jamaica. After a prolonged delay, releases of the host-specific, leaf-mining fly Calycomyza enputorivora from Jamaica commenced in South Africa in 2003. Studies completed on the stein-boring weevil Lixus aemulus, that originates from Brazil,have shown it to be host-specific and permission for release should be imminent. The root-feeding flea beetle Longitarsus horni from Venezuela and an unidentified stem-boring cerambycid recently collected from a Chromolaena species in Argentina are alsobeing cultured in quarantine. The stem-lip mining fly, Melanagromyza eupatoriella, from Florida, USA was successfully cultured for a few generations, but died out and a new culture will be imported from Jamaica to enable host-specificity testing. Othercandidate agents that have been imported but unsuccessfully cultured include the stem-galling fly Polymorphomyla basilica and two stem-tip boring moths, Mescinia sp. nr. parvula and an unidentified species. During the past two years, the defoliating mothPareuchaetes instulata from Florida, USA has been released in large numbers, for extended periods, at several sites in KwaZulu-Natat province in South Africa, with little establishment success. Populations of this insect from Jamaica and Cuba, which maybe more compatible with the southern African C. odorata biotype, will be released in a new attempt to achieve establishment in South Africa. Despite successful culluring for several generations, the stem-galling weevil, Canotrachelus reticulatus from Venezuela, died out in the laboratory, with biotype incompatibility a possible contributing factor. This agent will not be re-imported until further biology and host range studies have been conducted in the country of origin. Studies on the biology of thestem-tip mining sesiid moth, Carmenta sp. nov., will also be conducted in Venezuela. Also, studies on the biology and host-specificity of the stem-galling fly P. basilica, and other insect species on C. odorata, will commence in Jamaica once biotype compatibility has been determined In this regard, cooperation with overseas research organisations is of considerable importance in sustaining progress with the biological control of C. odorata.