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

Abstract

The lucerne flea, Sminthurus viridis (L.), is shown to be a pest of irrigated lucerne in the summerrainfall, 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 ≤ 13-15°C, 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.

Population Dynamics and Diapause Response of the Springtail Pest Sminthurus viridis (Collembola: Sminthuridae) in Southeastern Australia

“…The data presented here is consistent with previous studies (Davidson 1934, Wallace 1967, Bishop et al 2001a) with at least two generations of S. viridis occurring per season. Typically, an autumnÐwinter generation hatches from diapause eggs and another generation in spring lays diapause eggs.…”

“…Previous studies have consistently found two peak abundance periods that result from autumn emergence of the Þrst generation and then from favorable spring conditions (Davidson 1934, Wallace 1967, Bishop et al 2001a). However, considerable variation has been observed for the number of generations that occur, with between three and Þve relatively distinct generations reported (Davidson 1934, Wallace 1967, Bishop et al 2001a).…”

“…2). A generation was identiÞed as in previous studies (Davidson 1934, Bishop et al 2001a) by a large increase in the presence of nymphs. Additional third generations also were indicated by an increase in nymphal abundance at Irrewarra and in the irrigated plots at Bears Lagoon in both years.…”

“…Importantly, the diapause response of S. viridis also may be a potential target for control strategies. However, this requires a strong understanding of the S. viridis life cycle in Australia and despite previous investigations (Davidson 1934, Wallace 1967, Bishop et al 2001a, there is still ambiguity around the life cycle and a lack of current research. Furthermore, in the last decade S. viridis has signiÞcantly increased in prominence and has expanded its distribution in Australia (Bishop et al 1991).…”

“…However, considerable variation has been observed for the number of generations that occur, with between three and Þve relatively distinct generations reported (Davidson 1934, Wallace 1967, Bishop et al 2001a). In addition, the timing of emergence and cessation of the active stage can vary greatly between seasons and locations (Wallace 1967), whereas Bishop et al (2001a) observed hatching of nymphs throughout summer in irrigated lucerne, Medicago sativa L. This apparent plasticity in the S. viridis life cycle also may inßuence its diapause response. Since Þrst being demonstrated by Holdaway (1927), one study by Wallace (1968) has examined diapause in S. viridis in detail.…”