Effect of Several Stress Factors on the Susceptibility of the Predatory Mite, 'Metaseiulus occidentalis' (Acari: Phytoseiidae), to the Weak Bacterial Pathogen 'Serratia marcescens.'

摘要

A Metaseiulus occidentalis bioassay procedure that approaches incubation conditions for maximum host susceptibility to Serratia marcescens is presented. Preinoculation temperature and/or starvation pulses, chronic RH and crowding (or food search area) stressors, and an age (or instar) modulator were used singly and in combination to observe effects on the egg production and mortality of a predatory mite, M. occidentalis, inoculated with a weak bacterial pathogen, S. marcescens. Susceptibility of the mature host to the bacterium increased significantly after 4 days of incubation when the mite was exposed to a preinoculation high-temperature pulse and the containment area was increased. By day 6, these factors combined with incubation at high RH and some of their interactions significantly affected mite mortality and accounted for most of the variability in the experimental data. Although some of the stress factors significantly affected fecundity, as measured by egg production rate, inoculation with S. marcescens at doses up to 10(sup 8) colony-forming units/ml did not. (Copyright (c) 1988 by Academic Press, Inc.)