Distribution and ecology of the lucerne flea, Sminthurus viridis (L.) (Collembola : Sminthuridae), in irrigated lucerne in the Hunter dairying regionof New South Wales

The lucerne flea, Sminthurus viridis (L.), is shown to be a pest of irrigat ed lucerne in the summer-rainfall, temperate-type climate of the Hunter reg ion in New South Wales, an area previously considered unsuitable for its es tablishment. Main activity occurred at average temperatures less than or eq ual to 13-15 degreesC, resulting in five generations per season. Establishm ent and activity were closely related to irrigation. Eggs hatched throughou t summer but populations failed to develop. It was unclear if diapausing eg gs, the progressive hatching of non-diapausing aestivating eggs or both hel ped the species survive to form viable populations in winter. Early activit y was detected from catches of very small nymphs (< 0.3 +/- 0.14 mm) in pit fall traps, which preceded lucerne flea presence as small nymphs (< 0.82 +/ - 0.15 mm) on plants by approximately 2 weeks following irrigations or majo r rainfall. Predators and grazing by dairy cattle had no effect on lucerne flea numbers. Significant relationships were established between the lucern e flea and several plant growth and damage factors.