Incidences of lucerne flea

Some regions have received sufficient moisture for lucerne flea populations to challenge establishing crops.

A lucerne flea adult (Source: cesar).

 

Lucerne flea (Sminthurus viridis) population growth is highly dependent on moisture levels. They do very well in moist conditions or in dense pasture canopies, typically hatching after a soaking autumn rainfall.

Given that much of Victoria and NSW has experienced below average autumn rainfall, we do not expect lucerne flea will be a major issue for establishing crops in many regions.

Nevertheless, in some crops, typical lucerne flea ‘windowing’ damage has already been observed.

If seeds have been treated with Poncho Plus or Cruiser Opti, these will provide some protection of emerging crop seedlings against lucerne flea. However, under high pest populations, seed treatments alone will not be enough to withstand the feeding damage.

If you’re considering chemical control, consider the following questions:

Does the infestation warrant a blanket spray?

Lucerne fleas are patchily distributed within crops, so spot spraying is usually sufficient. Border sprays can also be effective in preventing the movement of individuals into crops from neighbouring paddocks. In addition to saving on chemical costs, these approaches limit the impact of insecticides on beneficial invertebrates (particularly predatory mites, which are voracious predators of lucerne flea) and reduces the selection for insecticide resistance building up in crop pests.

Are you also spraying for mites?

When lucerne flea and earth mites (e.g. redlegged earth mites, blue oat mites) are present, it is recommended that control strategies consider the species complex, and a product registered for all species is used at the highest directed label rate to ensure effective control. Remember, lucerne flea has a high natural tolerance to all synthetic pyrethroids and should not be treated with insecticides from this chemical class.

When did lucerne flea first emerge?

If the damage warrants control, treat the infested area with an insecticide 3 weeks after lucerne flea first emerges in autumn. This will allow for the hatching of most over-summering eggs and will target the nymphal stage before they reach maturity and begin to lay winter eggs. Newly hatched nymphs are pale yellow in colour in comparison to adults, which are light green-yellow and often have dark mottling over the body.

Are you observing any good guys?

The complex of beneficial species should be assessed before deciding on control options. Two effective predators of the lucerne flea are the pasture snout mite and the spiny snout mite (especially in pastures). Spiders and ground beetles also prey on lucerne flea.

The pasture snout mite is a predator of lucerne flea (Source: cesar).

 

Are you seeking further information on this pest? Visit our comprehensive lucerne flea PestNote.

 

Field reports of lucerne flea

Craig Muir – AGRIvision (Mallee, VIC)

Warwick Nightingale – Delta Agribusiness (Riverina, NSW)

Chris Toohey – Elders (Riverina, NSW)