Lucerne flea and other springtails

Grower, Evan Ryan, has experienced significant insect attack to a seedling lucerne crop near Yarrawonga, in the Northeast of Victoria. The pest has been identified by researcher, John Roberts (cesar), as Entmobrya unostrigata. This species is a collembolan (or ‘springtail’), belonging to the Family Entomobryidae. E. unostrigata is known to be an occasional pest of field crops and pastures. It is a slender insect, approximately 2-3 mm long when adults.  They have long antennae, prominent hairs and a well developed forcula (a specialised organ allowing springtails to ‘jump’ when threatened).  

Collembola are soil and litter dwelling insects that prefer wet, damp surroundings. They lack wings and always have antennae. They are among the most abundant of all soil-dwelling insects. Evan reports very high numbers of E. unostrigata were present within the affected paddock and that individuals could be seen directly feeding on lucerne seedlings.

Evan says these insects have not been a problem in previous years and believes the warm autumn conditions may have favoured the build-up of collembolan numbers. This pest was reported to survive an application of omethoate at crop establishment, although spray efficiency may have been compromised by the large amount of litter on the soil surface.

Grower, Robert Fraser, has reported lucerne flea (Sminthurus viridis) in a canola crop near Lake Bolac, in the Western district of Victoria. The lucerne flea, an important pest of winter grain crops in southern Australia, is also a collembolan.  Adult lucerne flea are approximately 3 mm in size and green-yellow in colour. They work up the plants from ground level, eating tissue from the underside of the foliage. They leave distinctive feeding damage of ‘windows’ of transparent leaf membrane and ‘spring’ off vegetation when disturbed.

Robert says large areas of the affected paddock were severely damaged and required re-sowing. If spraying for lucerne flea, it is recommended that growers assess the complex of beneficial species (including snout mites) present, and if spraying is necessary, do not use synthetic pyrethroids. Robert says dimethoate will be used to control this outbreak.

Click here for images of the lucerne flea.