ABSTRACT
This chapter looks briefly at the development of biological control for crown gall, discusses some of the successes and failures of its commercial application, and looks to ways in which it might be enhanced and its range extended. The causal organism, a Gram negative bacterium, Agrobacterium tumefaciens, is one of the relatively few soil-inhabiting bacterial plant pathogens. Susceptible plants are invaded only through wounds, usually at the crown or on the root system. The generally increased interest in nonpolluting and environmentally acceptable biological controls should facilitate registration of antagonistic organisms in the future, and previously fought battles for approval of strain 84 must surely have paved the way for its even more widespread registration. Strain 84 has also been maintained in 0.25% carboxymethyl cellulose for 10 months, but this leads to physiologically retarded cells that need to be used at higher than routine concentrations. The practicality of using freeze-dried cultures, having a long period of viability, has been under investigation.
