APPLICATION OF FORMULATED RHIZOBACTERIA AGAINST ROOT-ROT OF FIELD PEA

Formulations of bacterial biocontrol agents were evaluated for the con trol Of pea root-rot caused primarily by Pythium ultimum and Rhizocton ia solani, at different levels of disease severity in field trials. Ps eudomonas fluorescens (strain PRA25) in a peat-based formulation incre ased field by 17% over the untreated, in a trial with light disease in fection, and by 120% in another with moderate infection. Other bacteri a including P. cepacia (strain AMMD) and fluorescent pseudomonads incr eased seedling emergence, and decreased disease incidence and severity , but with variable effects on yield when disease level was light to m oderate. Biocontrol agents resulted in only limited control when disea se was severe, Control with Captan did not differ significantly from t hat obtained with bacterial biocontrol agents, The application of Rhiz obium granular inoculum together with PRA25 granules did not differ fr om other treatments in disease control, indicating that Rhizobium is c ompatible with biocontrol agents. The population dynamics of a fluores cent pseudomonad introduced into the rhizosphere in peat or granular f ormulation was monitored using an antibiotic-resistant mutant marker s train. The bacterium in pear formulation established a considerably hi gher population than that in granular formulation in 1993 trials, and a slightly higher population in 1994 trials. The higher population may have been responsible for the efficiency of root colonization and the effectiveness of disease control.