Population ecology of Halotydeus destructor in pastures

Abstract: High populations of Halotydeus destructor, averaging 20,000 mites/m2, are found in pastures over large regions of Australia, although abundance is patchy. Impact of this pest on pasture productivity is seen by substantial reductions in clover seed yield and in seedling survival. Mites feed in small aggregations of 3-38 individuals on a leaf, and aggregations are found in small patches (1-2 m) under tall pasture. High populations are also found in large patches (80 x 160 m) in pastures, which are considered to result from high levels of egg laying when food resources are favourable. Analysis of time series provided evidence for direct and delayed local density dependence. The delayed density dependence had a lag of 12-15 weeks (two generations). As winter progresses the locations of the large aggregations change from generation to generation. Mantel correlations indicate travelling waves of high population density whose peaks moved through the study site with time. Travelling waves could result from ecological interactions or seasonal forcing, or both.