Mass rearing an earth mite to screen plants for resistance: A review

Abstract

AbstractA mite which is polyphagous, widespread and abundant should be relatively easy to rear. However, mass rearing redlegged earth mite, Halotydeus destructor, for use in screening plants for resistance, has been very difficult. They are found in regions of Australia with winter growing annual crops and pastures, where they are active in winter and have a summer diapause. Mites are field collected in winter for screening, but cold storage only improves availability by 2 weeks. If mites are held in controlled climate cabinets under winter conditions with short daylength, the onset of diapause is not triggered and egg laying continues. Host plant suitability is a key factor affecting the rate of multiplication of mites, and common vetch, Vicia sativa cv Blanchefleur is an optimum host for rearing. The mites spend 90% of the time on the soil surface and only climb to the upper plant canopy in pastures to feed for 10% of the time. They are thus earth mites. High humidity at the soil surface is very important for their survival and optimal multiplication. If it is too wet dead mites on the surface are attacked by verticillium fungus, and active mites are adversely affected by hyphae. Mite multiplication is greater on well‐drained sandy loam soil than a loamy soil, sand or pure loam as a substrate. Mass rearing has now been achieved after overcoming these problems.