Development, survival, and reproduction of the predatory mite Kampimodromus aberrans (Acari: Phytoseiidae) at different constant temperatures.

Development, survival, and reproduction of the predatory mite Kampimodromus aberrans Oudemans were studied at constant temperatures in the range from 15 to 35 degrees C under laboratory conditions. Larval developmental rate for both males and females increased gradually from 15 to 35 degrees C and decreased at higher temperatures. Lactin's nonlinear model described with adequate accuracy the relationship between developmental rate and temperature. The model predicted that lower and upper threshold temperatures for preimaginal development ranged from 9.8 to 11.8 degrees C and from 37.2 to 39.8 degrees C, respectively. The intrinsic rate of population increase (rm) at the different temperatures ranged from 0.0442 to 0.1575, with the highest value recorded at 25 degrees C. At 33 degrees C a negative rm value was estimated. The rm values determined at different temperatures were fitted to Lactin's nonlinear model, and the lower and upper threshold and the optimal temperatures for population increase were 10.5, 32.4, and 27.6 degrees C, respectively. These data indicate that K. aberrans may be better adapted to intermediate temperatures around 27 degrees C and, therefore, could be a useful biocontrol agent of spider mites during spring and early summer when such temperatures are prevalent in northern Greece. The results could also be useful in developing a population model for K. aberrans under field conditions.

Development, survival and reproduction of Euseius finlandicus (Acari: Phytoseiidae) at different constant temperatures.

Development, survival and reproduction of Euseius finlandicus Oudemans were studied at seven constant temperatures (15, 20, 25, 27, 30, 32 and 34 degrees C) in the laboratory. Within the temperature range tested, developmental period from egg to adult varied from 148 to 360.5 h and 133.7 to 336.5 h for females and males, respectively. The lower thermal threshold for immature development for females and males was 8.9 and 6.4 degrees C, respectively. Survival during immature development exceeded 90% at all the temperatures from 15 to 32 degrees C, but at 34 degrees C an abrupt decline was recorded. Female longevity decreased gradually from 82.7 d at 15 degrees C to 12.2 d at 34 degrees C. The mean generation time ranged from 44.3 d at 15 degrees C to 15.9 d at 32 degrees C. The highest rm value (0.2817) was obtained at 30 degrees C and the lowest at 15 degrees C (0.0976). Temperatures above 30 degrees C had an adverse effect on population increase.

Rapid cold hardening in the predatory mite Euseius (Amblyseius) finlandicus (Acari: Phytoseiidae).

A rapid cold hardening response was studied in diapause and non-diapause females of the predatory mite Euseius finlandicus. When laboratory reared diapause and non-diapause females were transferred and maintained from the rearing temperature of 20 degrees C for 2 h to -11.5 degrees C and -10 degrees C, 10 to 20% survived respectively. However, conditioning of diapause females for 4 h at a range of temperatures from 0 to 10 degrees C before their exposure for 2 h to -11.5 degrees C, increased survival to approximately 90%. Similarly, conditioning of non-diapause females for 4 h at 5 degrees C before their exposure for 2 h to -10 degrees C increased survival to 90%. A similar rapid cold hardening response in both diapause and non-diapause females was also induced through gradual cooling of the mites, at a rate of approximately 0.4 degrees C per min. The rapid increase in cold tolerance after prior conditioning of the mites to low temperatures, was rapidly lost when they returned to a higher temperature of 20 degrees C. Rapid cold hardening extended the survival time of diapause and non-diapause females at sub-zero temperatures. The cost of rapid cold hardening in reproductive potential after diapause termination was negligible. In non-diapause females, however, the increase in cold tolerance gained through gradual cooling could not prevent cold shock injuries, as both fecundity and survival were reduced.

Functional response of Euseius finlandicus and Amblyseius andersoni to Panonychus ulmi on apple and peach leaves in the laboratory.

The functional response of adult females of the predatory mites Euseius (Amblyseius) finlandicus and Amblyseius andersoni to larvae and adult females of the fruit tree red spider mite Panonychus ulmi was determined on apple and peach leaf disks in the laboratory at 25 degrees C and 16:8 (L:D). For adult females of P. ulmi the predation efficiency of E. finlandicus was higher on peach than on apple, whereas that of A. andersoni was higher on apple than on peach. Efficiency of predation on larvae of P. ulmi by either predator did not differ significantly between apple and peach. On both plants, A. andersoni had a higher predation rate than E. finlandicus on larvae of P. ulmi. It is concluded that in the laboratory the host plant has a substantial effect on predation efficiency of A. andersoni and E. finlandicus when they preyed on adults but not when they preyed on larvae of P. ulmi.