A standard technique for detecting seed-borne pathogens in peas, chemical control, and testing commercial seed in South Australia

Abstract

A modified agar plate method was tested for its ability to detect Ascochyta pinodes, Macrophomina phaseolina, Phoma medicaginis var. Pinodella and Fusarium oxysporum on pea seed. It proved to be reliable. The characteristic colonies produced by the four pathogens from infected seeds on agar media are described. They were confirmed by microscopic examination. The method was used in a survey of 214 samples of commercial field pea seed from all parts of South Australia. Ninety per cent of samples had infection with A. pinodes with levels of infection ranging from 1-45%, making it the most important seed-borne pathogen. Seventy-two per cent of seed samples were infected with M. phaseolina with levels of infection ranging from 1-35%. Thirty-one and 24% of seed samples were infected with Phoma medicaginis and F. oxysporum, respectively. Only 10% of samples were free from infection. Two chemicals (benlate and thiram) were tested for in vitro control of these seed-borne pathogens. Complete control was achieved by thiram and benlate at both high and low dose rates.