Dispersal patterns of pest earth mites (Acari: Penthaleidae) in pastures and crops.

Control methods in pest earth mites and other mites often depend on low dispersal rates, yet there are no experimental estimates of these rates. To rectify this, adult movement rates were estimated in the earth mite Halotydeus destructor Tucker and the winter grain mite, Penthaleus major (Duges), using mark-release-recapture techniques. Mean square dispersal distances were used to estimate diffusion coefficients. In pasture, coefficients were in the range 0.3-1.3 for these species. This suggests that 90% of the population moves < 5-11 m in a 10-d period, or 7-16 m within their adult lifetime. Releases of mites in adjacent pea/wheat crops indicated directional movement toward the more favored pea host. However, there was no directional movement when adjacent plots of peas and lupins were compared, even though lupins are poor hosts. These results indicate that broad border sprays or border culturing will be needed to prevent mite movement from adjacent paddocks.