Ability of Phytoseiulus longipes to control spider mite pests on tomato in European greenhouses.

Even if many studies dealt with the biological control of spider mites on tomato in greenhouses, no efficient solution has still been found beyond chemicals to get rid of those phytophagous mites. Among them, two species, Tetranychus evansi and T. urticae, can be considered as very serious pests, leading to great damages in tomato crops in Southern Europe. Preliminary experiments showed that Phytoseiulus longipes is a very promising predator of these two species. In the present study, life tables of a Chilean strain of this predator have been calculated, at 25 °C, 80 ± 10 % RH and 16/ 8 (L/ D), in several prey/ plant conditions: P. longipes feeding on T. evansi on tomato, P. longipes feeding on T. urticae on tomato and P. longipes feeding on T. urticae on bean. 88.9 % of the predators did not complete their immature phase while feeding on T. evansi, and life tables could not be calculated. However, while feeding on T. urticae, immature survival was 99.8 % and 90.0 % on bean and tomato, respectively. Immature durations of P. longipes fed with T. urticae were not different, being 4.35 and 4.21 days, on bean and tomato, respectively. The intrinsic rate of increase (rm) was 0.368 and 0.116 female/ female/ day, on bean and tomato, respectively. Those results suggest that the Chilean strain of P. longipes would not be able to control neither T. evansi nor T. urticae in tomato crops. However, it seems able to eat and develop on T. urticae in other crops. Another strain of P. longipes, originating from Brazil, is currently being studied and lead to very enthusiastic perspectives to control spider mites on tomato greenhouses, both T. urticae and T. evansi. Furthermore, experiments are being conducted to try to explain the surprising differences in feeding habits and host plants between the two strains of this predaceous mite.