Lucerne flea

Seasons with dry or cool, wet conditions that slow plant growth have a higher risk of lucerne flea

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.

• Check damage levels and number of insects at least once weekly in crops, every 2 weeks in pasture, for the first 3-5 weeks after emergence.
• LF distribution can be very patchy, so check more sites than you might for other species (e.g. check plants in 50 cm row at 5-10 sites across paddock) – examine foliage for damage and soil surface where insects may shelter
• Monitor for other pest species at the same time (e.g. earth mites). Control decisions will need to take into account these species as well.

• pasture snout mite (Bdellodes lapidaria),
• spiny snout mite (Neomulgus capillatus)
• French anystis mite Anystis wallacei can provide effective suppression of lucerne flea.

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 .

Control alternative hosts to manage the overall LF population:

• Lucerne flea feeds on a range of broad-leafed weeds particularly capeweed
• Minimise weediness of fallows and pastures and control weeds around crop edges
• Crops are more likely to suffer damage where they follow a weedy crop or pasture where lucerne flea has not been controlled

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:

• Field selection – there is a low risk of lucerne flea occurring on sandy soils
• If in high risk area, consider using a higher sowing rate to compensate for seedling loss

• Canola: 10 holes per leaf (Vic)
• Establishing pasture: 15 per 100 cm² (sampling method not established, but could use that proposed by Taverner et al. 1996)
• A suggested threshold for other crops – treat if 50% of leaf area is likely to be damaged

• If earth mites are present, ensure species are identified. Not all insecticides registered for RLEM control are effective against LF.
• In pasture, consider the impact of insecticides on predatory mite species (if present)
• Timing spray to control the first generation in a crop or pasture (nymphs) will reduce the subsequent population growth in that paddock
• A border spray may be sufficient to control invasion from adjacent fields
• Extremely patchy infestations can be controlled with spot spraying, preventing population build-up and spread through the field
• TIMERITE® is not effective for the control of LF.
• Late season spraying can reduce number of insects in following autumn

Industry publications provide up to date regional information about pest activity in crops