The Hakea fruit weevil, Erytenna consputa Pascoe (Coleoptera: Curculionidae), and the biological control of Hakea sericea Schrader in South Africa

Abstract

Hakea sericea is a shrub, introduced into South Africa from southern Australia, that is now invading the indigenous "fynbos" vegetation in the Cape mountains. Presently an area of 480 000 hectares is affected. One of the main factors contributing to the success of H. sericea as a weed is its copious seed production. The seeds are accumulated on the plant throughout its life-time. When the plant eventually dies, usually after a fire, the fruits dehisce and all the seeds are released within the space of a few days, resulting in seed densities of up to 7 500 seeds per m². Dense, impenetrable stands of H. sericea develop which suppress the indigenous vegetation. Apart from the labour intensive mechanical clearing of H. sericea, biological control appears to be the only other means of control. This study deals with the post-release evaluation of the effectiveness of the first successfully-established, biological control agent, the hakea fruit weevil, Erytenna consputa. Most of the damage is done by the larval stage of the weevil which attacks the young developing fruits, thereby reducing seed production.