Monitor for redlegged earth mite

Conditions are now optimal for the redlegged earth mite (Halotydeus destructor, RLEM) activity across most regions of south-east Australia. Rainfall and cooler daily temperatures during the first half of May will have encouraged egg development and peak hatchings of RLEM.

Hatching of RLEM summer ‘diapause’ eggs are triggered by cooler temperatures and rainfall in autumn. Illustration: Elia Pirtle, cesar.

Establishing crops should be monitored regularly for the presences of mites and their damage. RLEM feeding causes silvering or white discoloration of leaves and distortion or shrivelling in severe infestations. Affected seedlings can die at emergence with high mite populations.

Mornings or overcast days are the best conditions to detect RLEM feeding on leaves. Broadleaf weeds, especially capeweed, are often a preferred host and RLEM numbers are commonly highest in weedy patches of paddocks.

When feeding, this species is often seen in large groups, a behaviour which distinguishes RLEM from other mite pest such as blue oat mites, Bryobia mites and the Balaustium mite, which tend to feed singly or in small numbers.

If mites are not present on foliage, inspect the soil also - only a small proportion of RLEM populations feed on foliage at any one time, with the large majority remaining on the soil surface.

Although some registered seed treatments provide early season protection against RLEM, sometimes noticeable damage may still occur. This is not due to insecticide resistance; RLEM have no known resistance to neonicotinoids or fipronil in Australia.

Rather, RLEM can be present in very high numbers, especially if coming out of a pasture rotation, and this increases the likelihood that some mites will take a ‘nibble’ on plants. What’s more, when RLEM feed, volatile chemicals are produced which encourages nearby mites to aggregate and feed.

For more information, including management and economic thresholds, visit this redlegged earth mite PestNote.