Relations between Typhlodromus caudiglans Schuster (Acarina: Phytoseiidae) and Phytophagous Mites in Ontario Peach Orchards

Abstract

In peach orchards undisturbed by pesticides and where phytophagous mites were at endemic densities, spring populations of Typhlodromus caudiglans were small and remained so during early summer until phytophagous mites, especially Aculus cornutus, began to increase. T. caudiglans reached maximal densities in September. In such orchards T. caudiglans appears to be an important factor in maintaining Panonychus ulmi at low density levels. On trees where DDT applied the previous year had caused P. ulmi to build up and which could be repopulated by T. caudiglans from neighbouring trees, the predator increased very rapidly but appeared to reach an upper limit of density fixed by intrinsic factors, possibly cannibalism. Under these conditions T. caudiglans could not bring P. ulmi to endemic densities in one season, though it appeared to slow the mite’s rate of increase and to reduce its maximal seasonal density.