Watch for Red Legged Earth Mites in Autumn

The Red Legged Earth Mite (RLEM) is starting to cause damage to dairy pastures across Victoria. Typical mite damage appears as ‘silvering’ or ‘whitening’ of the attacked foliage. RLEM are most damaging to newly establishing pastures and emerging crops, greatly reducing seedling survival and development. In severe cases, entire paddocks may need re-sowing following RLEM attack.

Caption: Typical damage caused by RLEM.

Earth mites are usually active in the cool, wet part of the year, usually between April and November and may pass through three generations, with each generation surviving six to eight weeks. RLEM eggs hatch in autumn following exposure to cooler temperatures and adequate rainfall. It takes about two weeks of exposure to favourable conditions for over-summering eggs to hatch. This releases swarms of mites, which attack delicate crop seedlings and emerging pasture plants.

RLEM hosts include pasture legumes, subterranean and other clovers, medics and lucerne. They are particularly damaging to seedlings of all legumes, oilseeds and lupins when in high numbers. They also feed on ryegrass and young cereal crops, especially oats. RLEM also feed on a range of weed species including Patersons’ curse, skeleton weed, variegated thistle, ox-tongue, smooth cats’ ear and capeweed.

RLEM feeding reduces the productivity of established plants and has been found to be directly responsible for reduction in pasture palatability to livestock. Carefully inspect susceptible pastures and crops from autumn to spring for the presence of mites and evidence of damage. It is especially important to inspect crops regularly in the first three to five weeks after sowing. Mites are best detected feeding on the leaves in the morning or on overcast days. In the warmer part of the day RLEM tend to gather at the base of plants, sheltering in leaf sheaths and under debris. They will crawl into cracks in the ground to avoid heat and cold. When disturbed during feeding they will drop to the ground and seek shelter.

Chemicals are the most commonly used control option against earth mites. While a number of chemicals are registered for control of active RLEM in pastures and crops, there are no currently registered pesticides that are effective against RLEM eggs.

Controlling first generation mites before they have a chance to lay eggs is the only effective way to avoid the need for a second spray. Hence, pesticides used at or after sowing should be applied within three weeks of the first appearance of mites, before adults begin to lay eggs. Timing of chemical application is critical. For more information on strategies to reduce RLEM damage or to treat slug infestations on your farm, discuss your situation with your local agronomist.