1 Department of Primary Industries, PO Box 48, Frankston, VIC 3199, Australia
Mesoclanis magnipalpis Bezzi (lacy-winged seed fly or LWSF) is a tephritid fly whose larvae live and pupate in the flowers and developing fruit of shrubs of the southern African genus Chrysanthemoides Tourn. ex Medik. LWSF is approved for use in Australia as a biological control agent for Chrysanthemoides monilifera (L.) T. Norl. C. monilifera comprises six subspecies of which ssp. monilifera (L.) T.Norl. (boneseed) is a serious weed in Australia and ssp. pisifera (L.) T. Norl. is restricted to South Africa. LWSF utilises both of these as hosts. From 1998 to 2005 four attempts were made to establish LWSF on boneseed in Australia. These attempts were made with LWSF collected from C. m. ssp. pisifera. However LWSF was not recovered except in the boneseed flowering/fruiting season of release, even though LWSF from those introductions readily oviposited on boneseed, and boneseed sustained development from egg to adult. A further introduction was attempted in 2009 with LWSF collected only from boneseed. This attempt to introduce the LWSF to Australia appears to have failed. Possible reasons for failure include, (i) successive flowering of different Chrysanthemoides subspecies is required for LWSF population survival, or (ii) LWSF collected from C. m. ssp. pisifera (pre-2009 importations) represented a biotype of LWSF whose life cycle was not synchronised with boneseed flowering. If (ii) is true then the failure of the most recent introduction might be due to releasing too few LWSF, or the release being too late in the boneseed flowering season.