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Field selection for tolerance to redlegged earthmite and lucerne flea in seedling Lucerne

I. Kaehne, E.T. Kobelt and B.M. Martin

Department of Agriculture, Northfield Research Laboratories, GPO Box 1671, Adelaide SA 5001

Redlegged earthmite (Halotydeus destructor) and lucerne flea (Sminthurus viridis) are major pests of lucerne in southern Australia. If high infestation of either occur, they can destroy establishing lucerne and severely damage re-growth in established stands. Higher levels of tolerance to these pests would reduce risk at establishment and reduce the cost of protection.


Lucerne cultivars and breeders lines were sown at 0.2 g seed/in' in 1 m x 5 m plots in a randomized block with four replicates at a site at Tintinara, South Australia, where earthmites and lucerne flea had consistently occurred at densities which severely reduced unprotected establishing lucerne. Results are reported from experiments sown in July in 1987 and 1989. The experiments were not treated with pesticide. Tolerance to pest attack was determined by measuring density of surviving seedlings on 29 September 1987 and 18 October 1989. On this latter date ratings for relative seedling vigour (0 = dead, 100 = best individual seedlings in experiment) and a rating of proportion of undamaged leaf area (0 = none, 100 = no damage) were also recorded.

Results and discussion

The densities and ratings for vigour and undamaged leaf area for two of the best breeders lines and the two cultivars are presented in Table 1. The breeders lines were developed from previous cycles of selection which commenced in 1982 at this site. A few individual plants within breeders lines were only slightly damaged under heavy infestation. It is probable that further gains can be achieved. There have been no survivors in cultivars under heavy pest infestation. Cultivars derived from the best breeders lines should reduce establishment risks and costs of pest control.

Table 1. Tolerance of lucerne cultivars and breeders lines to earthmite and lucerne flea.


This project was funded by the Meat and Wool Research Corporations.

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