The biology and host specificity of the Echium leaf miner Dialectica scalariella (Zeller) (Lepidoptera: Gracillariidae)

The gracillariid leaf miner Dialectica scalariella (Zell.), which occurs in Mediterranean Europe, North Africa, the Middle East and the Canaries, is a potential biological control agent for the weed Echium plantagineum in Australia. The moth has a high fecundity and oviposits on the leaves of Echium spp. and other Boraginaceae. The larvae destroy the leaves by forming large bulbous blotch mines. There are 5-7 generations per year. Host restriction of D. scalariella to Boraginaceae was tested by exposing a wide range of cultivated plants considered to be most at risk from it because of their close relation to Boraginaceae, because they were of Australian or non-European origin, because they did not occur in the same ecoclimatic region as D. scalariella , because their entomological fauna was poorly known, and because they or related plants were known to be attacked by insects closely related to D. scalariella . The host restriction of the moth was confirmed as only boraginaceous plants were attacked. It was concluded that both in terms of effectiveness and specificity D. scalariella could serve as a biological control agent in Australia for E. plantagineum .