Lucerne flea (Sminthurus viridis) in winter seedling crops and pastures (Southern Australia only).
- View diagram of lucerne flea lifecycle
|Objectives||Pre-plant||Seedling – Vegetative|
|Insects and damage||Lucerne flea (LF) survive summer as diapausing eggs which hatch in autumn when cool, moist conditions prevail. In spring, assess the weediness, and Lucerne flea (LF) abundance, in fallow or pasture into which a crop will be sown in autumn.
Seasons with dry or cool, wet conditions that slow plant growth have a higher risk of lucerne flea
|Broadleaf seedlings are most susceptible (canola, lupins, faba beans, field peas, clovers, lucerne). Grass species (wheat, oats, barley, pasture grasses) are less preferred hosts, but will damage seedlings.
Young nymphs feed on the soft tissue on the underside of leaves leaving transparent ‘windows’. Adults and older nymphs chew irregular holes in leaves and can completely defoliate plants
Look on the underside of foliage for lucerne flea; check for ‘windows’ of transparent leaf membranes.
Lucerne fleas jump when disturbed.
|Monitor and record||
|Natural enemies||Three species of predatory mites feed on lucerne flea. They include:
Some field experiments indicate a 70-90% control of lucerne fleas by predatory mites. Other reports suggest that predatory mite activity is rarely effective to reduce LF impact on seedling crops. Predatory mites are slow to spread and can only do so by crawling. Redistribution of predatory mites is possible using suction machines to collect and transfer mites from established to new sites. Other beneficials include ground beetles and spiders .
|Cultural control||Consider the risk of LF to establishing crops (especially canola, lupins, field peas) and pasture (clovers and lucerne) – e.g. previous occurrence and severity of LF in the paddock or on the farm. Consider management strategies for coming season including use of bare-earth treatments, seed dressings and the relative risk and monitoring requirements. Consider options for getting canola seedlings out of the ground as quickly as possible e.g. big seed, good soil-seed contact, planting as early as possible to avoid cold, wet conditions during emergence.
Control alternative hosts to manage the overall LF population:
Grazing management can reduce populations. Shorter pastures and lower relative humidity will increase insect mortality and limit food resources – however heavy grazing impacts more highly on predatory mites than lucerne fleas. Lightly grazed areas can act as a source of predatory mites.
Strip intercropping: Lucerne flea prefers lucerne and clover. Strip cropping with lucerne/clover may lower the risk of lucerne flea in other crops. Cultivation may reduce LF populations. There is a link between increasing LF abundance in cropping areas and the growing use of minimum and zero tillage practice. Other:
|Thresholds||Speculative thresholds: the key is early control because of the impact of seedling vigour on crop performance
|Multi-pest interactions||It is critical to manage LF in conjunction with other establishment pests, particularly the earth mite species. The use of broad spectrum insecticides for LF control may flare other pests e.g. aphids. A comparison of organophosphates and synthetic pyrethroids showed that only organophosphates were effective against lucerne flea – the application of SPs against mites can flare lucerne flea and also kills predatory mites|
|Communication||Consider how LF management may impact on earth mite abundance. Review and resistance management strategy recommendations for RLEM in relation to LF control options.
Industry publications provide up to date regional information about pest activity in crops
Bell, N. L. and B. E. Willoughby (2010). “A review of the role of predatory mites in the biological control of lucerne flea, Sminthurus viridis (L.) (Collembola: Sminthuridae) and their potential use in New Zealand.” New Zealand Journal of Agricultural Research 46(2): 141-146.
Taverner PD, Hopkins DC, Henry KR. 1996. A method for sampling lucerne flea, Sminthurus viridis L. (Collembola: Sminthuridae), in annual medic pastures. AJE 35: 197-199)