TRANSMISSION DYNAMICS OF BACILLUS-THURINGIENSIS INFECTING PLODIA-INTERPUNCTELLA - A TEST OF THE MASS-ACTION ASSUMPTION WITH AN INSECT PATHOGEN

Central to theoretical studies of host-pathogen population dynamics is a term describing transmission of the pathogen. This usually assumes that transmission is proportional to the density of infectious hosts o r particles and of susceptible individuals. We tested this assumption with the bacterial pathogen Bacillus thuringiensis infecting larvae of Plodia interpunctella, the Indian meal moth. Transmission was found t o increase in a more than linear way with host density in fourth and f ifth instar P. interpunctella, and to decrease with the density of inf ectious cadavers in the case of fifth instar larvae. Food availability was shown to play an important part in this process. Therefore, on a number of counts, the usual assumption was found not to apply in our e xperimental system.