Dialectica scalariella

Dialectica scalariella (Zeller, 1850)
(previously known as : Gracilaria scalariella)
Echium Leaf Miner
GRACILLARIINAE, GRACILLARIIDAE

Don Herbison-Evans ( donherbisonevans@yahoo.com )
&
Stella Crossley

(updated 3 November 2004)

(Photo: courtesy of the South Australian Research and Development Institute)

This Caterpillar was introduced deliberately from the Mediterranean region into Australia to control :

Paterson's Curse ( Echium plantagineum, BORAGINACEAE ),

which it attacks by mining the leaves. 'Paterson's Curse' was accidently introduced into Australia and is poisonous to cattle. However it is also known as 'Salvation Jane', as it is resistant to drought and is fodder for sheep in drought conditions. The flowers are also a good source of nectar for bees, and make the fields of NSW and South Australia an attractive and unusual purple colour when in flower.

Biological control was first suggested for Paterson's curse in 1928, but it was 42 years before anything was done about it. Then, in 1972, CSIRO began surveying the western Mediterranean region for natural enemies of the plant. One was the Caterpillar of Dialectica scalariella, and this was the first agent released (in 1980). It did not establish well, probably because of drought and grasshoppers. Shortly after the species was released, some beekeepers and graziers obtained a legal injunction preventing further releases. A legal battle followed for eight years. Eventually, the federal Government passed the 'Biological Control Act' in 1984. which prevents biological control programs being stopped by legal challenges if they aid the majority of the people. All state and territory governments passed complementary biological control legislation between 1986 and 1988. The injunction was then lifted in November 1988, allowing further releases of the moth. The moth was finally re-released in South Australia in 1988.

(Photo: courtesy of Ken Bond, Dept of Zoology, Ecology & Plant Science,
University College, National University of Ireland, Cork, Ireland)

The moth superficially resembles the Australian native species Dialectica aemula, which has made monitoring the progress of the species difficult, but the cocoons are more easily distinguished. The effects of increased Carbon Dioxide concentration on the species has been investigated.

The species has since invaded New Zealand accidentally.