Equipment and techniques for establishing field microplots for the study of soilborne pathogens.

(75% at p H 7.2 and 0 at p H 5.7 and 8.7). In our tests at 0.005 M concentration, host survival was 86-92% at all p H values, and no correlation was evident hetween host survival and pH. Many factors such as salinity, temperature, and pol lut ion can affect the efficiency of R. culicivorax. Although lower p H values appear to enhance the ability of the preparasi te to infect a host, p H is probably not a significant factor in most mosqui to habitats.