Biology and host range of the stem-boring beetle Aphanasium australe, a promising agent for the biological control of Hakea sericea in South Africa

Gordon, A.J.

BioControl Dordrecht 48(1): 113-122


DOI: 10.1023/a:1021245017334
Accession: 003661806

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The invasive Australian shrub Hakea sericea Shrader is a major environmental weed in the Western and Eastern Cape Provinces of South Africa. Dense, impenetrable thickets severely threaten the unique endemic vegetation of the Cape Floristic Kingdom, increase fire hazards and reduce water yields in catchments. Biological control, initiated in the 1970s, is largely confined to the use of seed-feeding insect agents. Because none of these agents reduce the density of existing hakea populations, a stem-boring beetle, Aphanasium australe (Boisduval) (Cerambycidae), was imported into quarantine in South Africa in 1975. During multichoice oviposition tests, involving 12 Australian and six South African proteaceous species, in a walk-in cage, A. australe only oviposited on four species of Hakea and two exotic species of Grevillea. However, culturing difficulties resulted in the suspension of host-specificity testing after three years. Testing was resumed following re-importations in 1995, also because A. australe also attacks Hakea gibbosa (Sm.) Cav., which is not attacked by any of the existing biocontrol agents. During no-choice survival tests, involving 66 test plant species from 15 families, A. australe only developed on H. sericea, H. gibbosa and one exotic species of Grevillea. The contention that A. australe is confined to the genus Hakea was confirmed by host records and surveys in Australia which provided no evidence of attacks on crop, pasture or related plants. The regulatory authorities accepted these results and A. australe was cleared for release in South Africa during 2001.