Nurit Shapira and Yael Argov

The efficacy of two predatory phytoseiid mites, Phytoseiulus persimilis and Neoseiulus californicus were compared for the biological control of Tetranychus urticae (TSSM) on greenhouse sweet peppers. We developed a simple and expedient rearing method for N. californicus solely on pollen. At the beginning of the trial there was a low-level spider mite infestation. Cohorts of P. persimilis (10/plant) and N. californicus (20/plant) were released in separate tunnels when the TSSM population was low and in additional tunnels 2 weeks thereafter. These treatments were compared with acaricide-treated and non-treated plants. Samples of leaves from the top and middle sections of plants from each tunnel were taken. There was no significant difference between the number of TSSM in the acaricide-treated and 1st N. californicus-release tunnels, but the number of TSSM in the acaricides-treated and P. persimilis-release tunnels were significantly different. At the higher spider mite population, there were significantly more TSSM in the P. persimilis release tunnels than in the N. californicus-release tunnels. We have confirmed laboratory trials and have shown that N. californicus is a superior TSSM predator at low humidities.