Pre-dispersal seed predation by Bruchidius villosus (Coleoptera, Bruchidae) in Laburnum anagyroides (Fabaceae, Genisteae)

The pre-dispersal seed predator, Bruchidius villosus (Coleoptera, Bruchidae) destroyed ca. 8% of seeds of its major host-plant, Laburnum anagyroides (Fabaceae, Genisteae), a tree-like legume, in Hungary. However, almost 40% of the pods were infested by the beetle. Females did not show a resource concentration response: with increasing number of seeds per pod, the number of uninfested seeds also increased. A high seed abortion rate of 75% left an average of two full-grown seeds per pod. Females laid three-four times more eggs on pods than the number of full-grown seeds present in a pod. Despite this, a high level (ca. 15%) of egg parasitism and pod abortion that reached levels up to 50% on pods which already bore bruchid eggs, decreased the infestation level. Larval parasitisation rate of B. villosus by chalcids and braconids exceeded 30%. Nomenclature for plants follows: Tutin et al. (1968). tonio 2003) that rapidly change the stability and structure of the community which they enter. Bruchidius villosus (F.), a pre-dispersal seed predator in the tribe of Genisteae, has been intensively studied in New Zealand where it is used as a biological control agent for C. scoparius (Syrett et al. 2000, Syrett and O’Donnell 1987, Harman 1999, Haines et al. 2004). Studies on the beetle were also conducted in the UK (Parnell 1966, Waloff 1968, Syrett and O’Donnell 1987) where C. scoparius was a common host to B. villosus and results suggested that it was host specific to this plant. Until this study, the effect of the pre-dispersal seed predator on plant performance of golden rain, Laburnum anagyroides, has not been known. Therefore, the aims of the present paper were: to provide data on the phenology and pre-dispersal seed predation of one of the major hosts of B. villosus in Hungary; to find out whether the pre-dispersal seed predator utilizes the usually considerable seed crop of this perennial legume by a density dependent manner, and to give information on the biology of B. villosus for biological control projects where it is used as a natural enemy against introduced legume weeds. Materials and methods