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

Gordon, Antony John (1993) The biological control of Hakea sericea Schrader by the Hakea seed-moth, Carposina autologa Meyrick, in South Africa. Masters thesis, Rhodes University.

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Abstract

Hakea sericea Schrader was introduced to South Africa from Australia and has become a major problem in nearly all the coastal mountain ranges of the Cape Province. The hakea seed-moth, Carposina autologa Meyrick was released in South Africa for the biological control of H. sericea. The impact of the moth on the canopy-stored seeds of H. sericea was evaluated at two study sites in the south-western Cape over three years. The moth has reduced the accumulated seeds at the two study sites by 59.4% and 42.6%, respectively. The moth 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 attacked fruits. Only 13.1% of the healthy fruits with eggs yielded mature larvae. The high pre-penetration mortality found in the present study is similar to that found in Australia. The effect of the indigenous fungus, Colletotrichum gloeosporioides (Penz.) Sacc., on both H. sericea and C. autologa was investigated. H. sericea trees and branches that die as a result of fungus cause the accumulated fruits on the affected trees or branches to dehisce. This seed loss occurs at a crucial stage during C. autologa larval development. Only 42.1% and 33.0% of the trees were found to 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 occur at a stage when the latest seed crop has escaped attack by c. autologa. C. autologa was released at six sites in the south-western Cape by attaching egg-bearing follicles to healthy fruits in the field. Three release sites were evaluated the year following release to determine whether the 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.

Item Type:Thesis (Masters)
Uncontrolled Keywords:Hakea sericea Schrader, Coastal mountain ranges, Cape Province, South Africa, Hakea seed-moth, Carposina autologa Meyrick, Impact, Seeds, Reduction, Colonies, Fruit, Larvae, Fungus, Colletotrichum gloeosporioides (Penz.) Sacc., Role, Follicles
Subjects:Q Science > QL Zoology > Invertebrates > Insects
Q Science > QL Zoology
S Agriculture > SB Plant culture
Divisions:Faculty > Faculty of Science > Zoology & Entomology
Supervisors:Hulley, P.E.
ID Code:4086
Deposited By: Philip Clarke
Deposited On:19 Nov 2012 06:11
Last Modified:19 Nov 2012 06:11
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