Biological control of plant diseases - present and future trends

Abstract

Foliar pathogens are not easy to control using biological agents because of difficulties in ensuring their persistence. Species of Bacillus and Pseudomonas controlled some fungal pathogens and yeasts and Trichoderma spp. limited necrotrophic pathogens. Bacterial pathogens were controlled by related saprophytes. Root diseases offer greater potential for biocontrol. Pythium diseases were suppressed by bacteria. A Chaetornium and an unidentified basidiomycete significantly reduced wheat take-all. Zygorrhynchus moelleri inhibited the growth of Rhizoctonia and Pythiwn by producing (b-1,3-glucanases and an antifungal indole compound, indole-3-ethanol. Z. moelleri enhanced root and shoot growth and caused earlier flowering and fruiting of horticultural plants. There are good prospects for biocontrol of many seed-borne diseases. Of a range of microorganisms applied to linseed seeds to control the pathogen Alternaria linicola, an isolate of Bacillus sp. and Trichoderma harzianum were the most effective. Various additives to alginate pellets can greatly extend the persistence of biocontrol organisms.