Biology and host specificity of the Chondrilla root moth Bradyrrhoa gilveolella (Treitschke) (Lepidoptera, Phycitidae)

The biology and ecology of Bradyrrhoa gilveolella (Treitschke), recently introduced into Australia as a possible biological control agent for the composite Chondrilla juncea, is described for Greece and compared with its known biology in southern Russia. The moth occurs from eastern Europe to southern Russia. In Greece it has two full and possibly a partial third generation each year. Its larvae live in cases below the soil surface and feed on the rootstocks of Chondrilla spp., destroying the thinnest plants. Heavy larval infestations on Chondrilla occur erratically in eastern Greece, being dependent on sites on sandy or very friable soils that are only occasionally disturbed; populations in hotter southern Greece appear to be less stable than those in the cooler northern regions. The larvae are heavily attacked by the fungus Beauveria bassiana as well as by Bracon sp., Copidosoma sp. and Syzeuctus sp. (Hymenoptera) and by the Tachinid Germaria graeca (Br. & Berg.); these cause a total larval and pupal mortality of up to 80%. Host specificity studies, during which the roots of various wild and cultivated composites and 62 cultivated plants were exposed to the moth larvae, showed that only Chondrilla and the closely related genus Taraxacum were attacked. A field survey showed that Taraxacum was not a host under natural conditions. All forms of C. juncea were equally readily attacked by B. gilveolella larvae.