Earth mites

This season we have received relatively few reports of several common earth mites, including the redlegged earth mite and blue oat mite. Whilst it is unclear exactly what has influenced this seasonal pattern, it is likely that the high spring and summer rainfall experienced in 2010/2011 in many areas had an adverse effect on the production and survival of over-summering diapause eggs. Research agronomist, Simon Craig (BCG), reports recently observing high numbers of redlegged earth mites in a wheat crop north west of Swan Hill, but says the overall number of mite issues in the Victorian Mallee has been unusually low this season.

As most crops are now well established, earth mites are unlikely to pose many further problems this season as crops and pastures will generally be able to outgrow the feeding damage. It is however a good time to start thinking about potential mite issues for next season. For redlegged earth mites, control can be timed to occur during a short window of the season - during spring - when mites 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 season). This approach can significantly reduce redlegged earth mite numbers the following autumn.

The optimum ‘spring-spray’ dates for redlegged earth mites in eastern Australia are mostly between mid-September and mid-October, and are freely available from the Timerite^® website. Some examples of the recommended dates are: Swan Hill - 12^th Sep, Horsham - 23^rd Sep, Bendigo - 28^th Sep, Wagga Wagga - 29^th Sep, Dubbo - 14^th Oct, and Colac - 16^th Oct.

The date is based on geographical location and is therefore unique to each property. It is recommended that spraying be carried out within the two-week period before the optimal date. The use of Timerite^® should be considered in paddocks where redlegged earth mites are a continual problem.

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. Before using this approach, consideration should also be given to the actual number of mites present and the susceptibility of the crop to be sown next season.