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

The lucerne flea, Sminthurus viridis (L.), is shown to be a pest of irrigated lucerne in the summer-rainfall, temperate-type climate of the Hunter region in New South Wales, an area previously considered unsuitable for its establishment. Main activity occurred at average temperatures less than or equal to 13-15 degreesC, resulting in five generations per season. Establishment and activity were closely related to irrigation. Eggs hatched throughout summer but populations failed to develop. It was unclear if diapausing eggs, the progressive hatching of non-diapausing aestivating eggs or both helped the species survive to form viable populations in winter. Early activity was detected from catches of very small nymphs (< 0.3 +/- 0.14 mm) in pitfall traps, which preceded lucerne flea presence as small nymphs (< 0.82 +/- 0.15 mm) on plants by approximately 2 weeks following irrigations or major rainfall. Predators and grazing by dairy cattle had no effect on lucerne flea numbers. Significant relationships were established between the lucerne flea and several plant growth and damage factors.