Vertical Distribution of Parasitizing on in Florida.

is considered as the primary agent responsible for soil suppressiveness to root-knot nematodes widely distributed in many agricultural fields. A preliminary survey on a field where the grower had experienced a continuous decline in productivity caused by showed that the nematode was infected with . For effective control of the nematode, the bacterium and the host must coexist in the same root zone. The vertical distribution of and its relationship with the nematode host in the soil was investigated to identify (i) the vertical distribution of endospores in an irrigated field and (ii) the relationship among endospore density, J2 population density, and host plant root distribution over time. Soil bioassays revealed that endospore density was greater in the upper 18 cm of the top soil compared with the underlying depths. A correlation analysis showed that the endospore density was positively related to the J2 population density and host plant root distribution. Thus, the vertical distribution of was largely dependent on its nematode host which in turn was determined by the distribution of the host plant roots. The was predominant mostly in the upper layers of the soil where their nematode host and the plant host roots are abundant, a factor which may be a critical consideration when using as a nematode biological control agent.