The influence of the lucerne bud mite (Eriophyes medicaginis Keifer) on the growth of annual and perennial Medicago species

Abstract

Studies were made of the influence of E. medicaginis on the growth of 11 wild or cultivated lines of perennial Medicago, embracing seven species, and one cultivar of each of the annual species M. littoralis and M. truncatula.

Mite infestation of the perennial species caused significant (P < 0.05) reduction in shoot dry weight of six of the 11 lines. It did not significantly influence leaf number and generally did not reduce stem length. However, it caused significant (P < 0.05) reduction in petiole length in most of the lines. Mite infestation of annual species caused highly significant (P < 0.01) reductions in shoot dry weight and produced leaf symptoms similar to some of those observed on the perennial species.

Mites reproduced on all species, but to a greater extent on the perennials than the annuals. There were no significant differences in either mite or egg numbers per seedling amongst the perennial species, 26 days after infestation with 10 mites per seedling.

The occurrence of symptomless plants bearing high mite numbers amongst the perennial species, M. coerulea, M. falcata, M. glutinosa, M. hemicycla and M. quasifalcata, suggested the presence of physiological tolerance to the mite within these species.