Ecology of Rhopalomyia californica Felt at Jasper Ridge (Diptera: Cecidomyiidae).
Rhopalomyia californica develops in terminal galls on Baccharis pilularis in California and is under investigation as a possible biological control agent against related species of Baccharis that are rangeland weeds in Texas and Australia. An ecological study of the cecidomyiid in California in 1982-83 suggested that predators and parasitoids were largely instrumental in maintaining the population density at a low level, especially 2 species of Torymidae, 2 of Pteromalidae and 1 each of Eulophidae, Eupelmidae and Platygasteridae. Bait-sprays with a malathion base applied to an adjacent area resulted in a massive outbreak of R. californica and also altered the spatial structure of the population. For its successful introduction and establishment as a biological control agent in Texas or Australia, care would have to be taken not to introduce its natural enemies with it.