2.1. Functional response of N. barkeri on F. occidentalis
treated by B. bassiana
The number of B. bassiana conidia (CFU) recovered from
the surface of the first instar was 1.9×103 CFU per insect.
The functional response for N. barkeri on F. occidentalis
which were treated by B. bassiana for two different periods
was successfully fitted to the Holling II disk equation. The
predation rate tended to increase with increasing prey
density and displayed curvilinear rise to a plateau as seen
in each treatment (Tables 1–2 and Fig. 1). For prey which
had been treated 12 h previously, compared to the control,
the mean number of prey consumed per mite was significantly
higher when prey densities were between 15 and 20
prey. In contrast, significantly less prey was consumed at
treated prey densities of 25. No significant differences were
found when prey densities were 15 and 20 prey which had
been treated 24 h previously. Attack rate of mites was the
highest in control.