Studies on Predator-Prey Interactions Between Amblyseius hibisci and Oligonychus punicae (Acarina: Phytoseiidae, Tetranychidae) Under Greenhouse Conditions1

Abstract

An experiment was conducted in the greenhouse on seedlings of Persea indica Spreng to determine the ability of the predaccous mite Amblyseius hibisci (Chant) to suppress populations of the phytophagous mite Oligonychus punicae (Hirst) both in the presence and in the absence of pollen as an alternate food. On the predator-free check plants, the prey population underwent 4 fluctuations in abundance over a 46-wcek period; the magnitude of the initial fluctuation was considerably higher than subsequent fluctuations. It was concluded that this population was regulated by the condition of its food supply. On the plants having predators but no pollen, the prey population during the first 2 fluctuations reached peaks as high as those on the predator-free plants, although the leaves showed slightly less damage. The greatest effect of the predator in the absence of pollen occurred after the second peak of prey abundance; the prey population continued to decline while that on the predator-free plants underwent a third fluctuation. However, the predator population then declined to low numbers and subsequently did not respond numerically to a third fluctuation in prey abundance that occurred concurrent with the fourth fluctuation on the predator-free plants. On the plants receiving periodic applications of pollen, the prey population density peaked at less than half that on the trees without pollen, and declined sooner, after which no further significant increases occurred. It was thus demonstrated that alternate food increased the intensity of predation because it accelerated the rate of increase of the predator. The greater numbers of predators produced by pollen feeding more than offset the lower rate of prey consumption per individual predator.