A virosis-like proliferation (Witches' broom) of lucerne (Medicago sativa L.) caused by an eriophyid mite (Aceria medicaginis Keifer)

Abstract

A witches' broom condition of lucerne, characterized by foliage symptoms similar to those attributed to a leafhopper-transmitted virus, is described.

The lucerne bud mite, Aceria medicaginis Keifer, has been found to be consistently associated with affected plants collected in a number of localities in northern Victoria.

Mites transferred to healthy lucerne seedlings induced the leaf and foliage proliferation symptoms observed on field-collected plants. Experimentally and naturally affected plants recovered when sprayed with thiometon, which indicated that the mite was not acting as the vector of a virus.

This previously unreported association of eriophyid mites with witches' broom of lucerne is discussed in relation to findings from earlier aetiological and ecological studies on the disease in Australia.