Relationship between temperature and development of Galendromus flumenis (Acari: Phytoseiidae), a predator of Banks grass mite (Acari: Tetranychidae).

The Banks grass mite, Oligonychus pratensis (Banks) (Acari: Tetranychidae), is a serious pest of grains, grasses and dates. In order to develop and optimize biological control strategies against the Banks grass mite, the survival and development of the predator, Galendromus flumenis (Chant) (Acari: Phytoseiidae), at eleven constant temperatures between 12 and 44°C were determined. The survival rates of G. flumenis (67.4-89.5 %) were highest between 26 and 38°C although it developed successfully from egg to adult at temperatures ranging from 18 to 42°C. The lower temperature threshold (T 0 ) and thermal constant (K) for total immature development were 13.3°C and 145.3 degree-days, respectively. The upper temperature threshold was 44.3°C, and the optimal temperature for development was calculated to be 37.5°C. These results indicate that G. flumenis is better adapted to high temperatures than most predators in the Phytoseiidae. In addition, the thermal requirements for total development of G. flumenis was found to be very close to those of O. pratensis which indicates that there should be synchrony between the occurrence of the prey and the predator. Therefore, the lack of predation observed in the field is related to other factors, such as the developmental time between O. pratensis and G. flumenis, or the inability of the predator to establish at the same time, and in the same location, as the prey.