Lucerne Flea

Sminthurus viridis

Family: Sminthuridae

Order: Collembola

Description:

Colour Variable and often green or yellow. Often with a white stripe down their back.

Body -Stout and globular. Soft. 2-4 mm long, 2-4 mm wide.

Wings - None.

Mouthparts - chewing.

Antennae - 4 segments

Legs - 5-6 segments

Head - primitive eyes with 8 ocelli

Thorax - 3 segments

Abdomen - Globular. 6 segments. Has a spring tail for jumping on segment 4.

Egg - Spherical, pale and smooth

Nymph - 5-6 instars. 0.5 mm long when born. They look like a small version of the adult.

Habits - Jumps up to 30cm high when approached.

Biology:

Life Cycle:

Over summering eggs hatch with the break of the winter season and pass through 3-9 nymphal stages to become adults within 3-5 weeks. Females lay several batches of eggs in the soil which hatch a few days later. There are 3-4 generations from autumn to late spring. Over summering eggs are laid in spring and hatch with the break of the season in autumn. Adults are killed by hot weather in early summer.

Populations peak in autumn, fall in winter and peak again in spring.

Habitats:

Clayey soils.

Origin and History:

European origin. They were probably introduced to Australia in 1933.

Distribution:

They are most prevalent in areas with a Mediterranean climate and winter rainfall. They are a major pest in southern NSW, SA, Vic, Tas and WA.

They are limited by the 250 mm isohyet for May-October rainfall.

They only occur on soils with significant clay content.

Significance:

A serious pest of Lucerne, legume pastures, capeweed, legume crops, cereals and ryegrass. Seedling deaths may occur in heavy infestations. Mature plants are retarded as the leaf material is removed leaving the leaf as a white film or they leave holes or windows in the leaf. It is a cool season pest often associated with Redlegged Earth Mite. Damage is often patchy and usually on the heavier soil types.

Management and Control:

Systemic and contact insecticides are used for control.

It is rarely a problem on sandy soils. On heavier soils control is often practised.

Predatory mites provide some control. Population density may also be regulated by juveniles feeding on recently deceased adults that shortens their life span. High densities are regulated by cannibalism. The use of synthetic pyrethroid sprays for controlling other pests often leads to an increase in Lucerne Flea.

Thresholds:

In established Lucerne more than 50 fleas per 5 m sweep on an insect net is required before control is warranted. In seedling stands it is worth using seed dressings or spraying when 1-2 fleas are found on each seedling.

In young Canola spray when more than 10 holes per leaf are found. Lucerne flea is often patchy in its distribution so check the whole paddock for signs of damage. Damage appears as window like holes in the leaf.

Biocontrol:

Bdellodes lapidaria, a mite from the Bdellidae family has been introduced as a biocontrol agent.

CSIRO has introduced other predatory mites to assist with control.

Related Species:

None of economic importance.

Similar Species:

References:

CSIRO. The Insects of Australia. Melbourne University Press. (1991) p207, 256, 257, 264.

Child, J.C. Australian Insects. Periwinkle Books. p17.

WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185. p61.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.