Redlegged earth mites and spring spraying

Jon Shuter (NSW TAFE) has reported high numbers of redlegged earth mites (Halotydeus destructor) in two pasture paddocks near Wagga Wagga, in the South West Slopes of New South Wales. Jon says feeding damage was mostly on lucerne and subclover, although mites were predominantly observed on ryegrass, with up to 12 individuals per plant. The paddocks were sprayed with omethoate due to the extent of feeding damage and high mite densities.

Agronomist, Craig Drum (Elders), reports a high number of redlegged earth mites attacking a wheat crop near Charlton, in the Wimmera district of Victoria. Craig says the mites have caused typical damage which appears as ‘silvering’ or ‘whitening’ of the attacked foliage. Consultant, John Robertson (Agwise Services), has also reported redlegged earth mites within many cereal crops throughout the Wimmera district of Victoria.

Redlegged earth mite populations typically build-up in spring, so it is important to keep an eye out. Control can be timed to occur during a short window of the season - during spring - when they have ceased laying winter eggs (eggs that must hatch this season) and before they start laying diapause eggs (over-summering eggs that survive until next autumn). This approach reduces redlegged earth mite numbers the following autumn.

The optimum ‘spring-spray’ dates for redlegged earth mite control in south-eastern Australia are mostly between mid-September to mid-October. Exact dates are available through the Timerite® model, which was developed by CSIRO. Timerite® packages are available free from www.timerite.com.au or by phoning the Australian Wool Innovation helpline on 1800 070 099.

The date for spring spraying is unique to each farm and remains constant from year to year. It is recommended that spraying be carried out within the two week period before the optimal date. Some examples of the ideal date are: Horsham (Victoria) - 23^rd September; Benalla (Victoria) - 12^th October; Wagga Wagga (NSW) - 29^th September; and Dubbo (NSW) - 14^th October.

Correct identification of mites before deciding to spray is important. Timerite® is designed to only control redlegged earth mites; it will not effectively control other pests, such as blue oat mites. Click here for images of redlegged earth mites and refer to PestFacts Issue No. 2 for further information.