Lucerne flea revels in the rain

It’s been a big year for lucerne flea, but spot spraying is often all that’s necessary

 

Where have they been reported?

Reports of major feeding damage from lucerne flea (Sminthurus viridis) in new and established lucerne pastures have come in from the Wellington region of the NSW Central West Slopes and Plains. Similarly widespread crop damage has been reported in lucerne northeast of Albury in the NSW Riverina, and in grass/clover pastures southeast of Kerang in Victoria’s Northern Country. Wet conditions have not only provided an optimal environment for populations to thrive, in some cases they have hindered access to paddocks to control them.

About lucerne flea

Lucerne fleas move up plants from ground level, eating tissue from the underside of foliage. They feed through a rasping process, leaving behind a thin clear layer of leaf membrane that appears as transparent ‘windows’ through the leaf.

Adult lucerne flea (left) and the typical ‘window’ feeding damage (right) (Source: cesar)

 

Depending on temperatures and moisture availability, lucerne flea can have up to 6 generations per year between autumn and spring. The length of each generation varies from 3-5 weeks. The first generation often hatches from over-summering eggs in March-April after adequate autumn rainfall. In late spring lucerne fleas will typically die off from the onset of warmer weather leaving over-summering eggs on soil surface. The rate of growth of lucerne flea populations is very moisture dependent; they do well in moist conditions or under dense canopies of pasture. 

Want to know more about lucerne flea? Visit our PestNote for further information.

Our advice

The complex of beneficial species should be assessed before deciding on control options. The pasture snout mite and spiny snout mite are effective predators, particularly in pastures where they can prevent pest outbreaks. Spiders and ground beetles also prey on lucerne flea.

Characteristically, lucerne fleas are often patchily distributed within crops, so spot spraying may be sufficient. Do not blanket spray unless the infestation warrants it. 

Lucerne fleas have a high natural tolerance to synthetic pyrethroids and should not be treated with insecticides from this chemical class.

 

Sources of field reports of lucerne flea

Rebecca Bingley – Agronomist, Landmark (NSW Riverina)

Jack Edwards – Agronomist, D&J Rural Services (NSW Central West Slopes & Plains)

James Maino – Researcher, cesar