The biological control of Hakea sericea Schrader by the Hakea seed-moth, Carposina autologa Meyrick, in South Africa

摘要

Hakea sericea Schrader was introduced to South Africa fromAustralia and has become a major problem in nearly all thecoastal mountain ranges of the Cape Province. The hakeaseed-moth, Carposina autologa Meyrick was released in SouthAfrica for the biological control of H. sericea. The impactof the moth on the canopy-stored seeds of H. sericea wasevaluated at two study sites in the south-western Cape overthree years. The moth has reduced the accumulated seeds atthe two study sites by 59.4% and 42.6%, respectively. Themoth has shown a surprising ability to disperse and establish new colonies at low population levels. Factors contributing to the slow colonization of C. autologa in South Africa was investigated. The moths appear to be unable to distinguish between healthy and previously attacked fruits; 42.5% of the eggs were laid on attackedfruits. Only 13.1% of the healthy fruits with eggs yieldedmature larvae. The high pre-penetration mortality found inthe present study is similar to that found in Australia. The effect of the indigenous fungus, Colletotrichumgloeosporioides (Penz.) Sacc., on both H. sericea andC. autologa was investigated. H. sericea trees and branchesthat die as a result of fungus cause the accumulated fruitson the affected trees or branches to dehisce. This seedloss occurs at a crucial stage during C. autologa larvaldevelopment. Only 42.1% and 33.0% of the trees were foundto be healthy at the two study sites, respectively.One seed crop will always be available for regeneration,since recruitment is linked to fires, and wild-fires occurat a stage when the latest seed crop has escaped attack byc. autologa. C. autologa was released at six sites in thesouth-western Cape by attaching egg-bearing follicles tohealthy fruits in the field. Three release sites wereevaluated the year following release to determine whetherthe moth established or not. The role of C. autologa in the H. sericea biological control programme is discussed. Although seed destruction by C. autologa is not severe, it is expected to contribute to the control of H. sericea.