Predatory performance of two Mediterranean phytoseiid species, Typhlodromus laurentii and Typhlodromus rhenanoides fed on eggs of Panonychus citri and Tetranychus urticae

Laboratory trials were carried out to determine the predatory capacity of two endemic to the Mediterranean area phytoseiid mites Typhlodromus (Typhlodromus) laurentii Ragusa et Swirski and Typhlodromus (Anthoseius) rhenanoides Athias-Henriot (Parasitiformes Phytoseiidae) upon the eggs of the two most important tetranychids damaging Citrus orchards in Sicily: Tetranychus urticae Koch and Panonychus citri (McGregor) (Acariformes Tetranychidae). The research aimed at investigating the predatory behaviour of the phytoseiids upon the prey stage considered the most vulnerable. The predation rate of the two phytoseiid species was different on the two prey eggs, both in every observation day and for the whole observation period. Both phytoseiid species have showed a better performance on T. urticae eggs, on which the predation rate was significantly higher for T. laurentii (12.53 ± 0.28 preyed eggs/female/day), than for T. rhenanoides (9.71±0.22 preyed eggs/female/day). On the opposite, the predation upon P. citri eggs was very limited, without substantial differences between the two phytoseiids: 0.54 ± 0.09 and 0.21 ± 0.04 eggs/female/day for T. laurentii, and T. rhenanoides respectively. The prey provided has also affected the oviposition rate of the two phytoseiid species. T. laurentii was the most prolific species with 2.13 ± 0.08 eggs/female/day, when eggs of T. urticae were supplied as food, while upon P. citri eggs only 0.31 ± 0.05 eggs/female/day was laid by this predator. The oviposition rate of T. rhenanoides on T. urticae eggs (1.31 ± 0.07 eggs/female/day) was significantly lower, if compared to that of T. laurentii (2.13 ± 0.08 eggs/female/day). However, no significant difference was found when the phytoseiids preyed upon P. citri eggs.