Specialized predatory strategies by Phytoseiulus macropilis and Neoseiulus californicus: implications for optimal biological control of Tetranychus urticae

Tetranychus urticae Koch (Acari: Tetranychidae) is a key pest in various crops. Biological control with Neoseiulus californicus (McGregor) and Phytoseiulus macropilis Banks (Acari: Phytoseiidae) is promising, but predator–prey interactions need to be better understood. The present study was designed to compare the consumption rate and functional responses (FRs) of N. californicus and P. macropilis at low densities of T. urticae. To compare the FRs of N. californicus vs. P. macropilis on T. urticae, five densities (3, 5, 10, 15, 20 individuals per trial) of this prey were offered at adult stage. The prey was added to the experimental arena containing a single predatory mite that was allowed four days (i.e., 96 h) to consume prey without replacement of consumed individuals. Observations were carried out once a day (24 h, 48 h, 72 h and 96 h). The numbers of prey consumed, and eggs laid were counted every 24 h. Results indicate that both predator curves align with a Type II FR. P. macropilis was faster at attacking T. urticae but slower at handling it. Lower egg production by T. urticae indicates that P. macropilis seems to be more effective in controlling this prey compared to N. californicus. Conversely, N. californicus was faster at handling prey and performed comparably to P. macropilis at higher prey densities. Therefore, depending on the specific circumstances of pest infestation, both predators present viable options for the biological control of T. urticae, with P. macropilis excelling in low-density scenarios and N. californicus offering effectiveness at slightly higher densities.