Formulation and pathogenicity of a bioherbicide for wild poinsettia control

Adequate formulation of bioproducts represents one of the most challenging aspects of bioproduct development. The incorporation of adjuvants with bioagents can positively influence product development. However, it is indispensable to evaluate the sensitivity of bioagents to these adjuvants. The aim of this study was to determine the toxicity of seven adjuvants at different concentrations to Bipolaris yamadae (Bipolaris euphorbiae) fungus, to select a product compatible with this phytopathogen for a wettable powder formulation and to evaluate the pathogenicity of the formulation against wild poinsettia (Euphorbia heterophylla). The powder fraction of the formulation was made up of 1% anti-wetting silicon dioxide mixed with B. yamadae conidia to a final concentration of 107 conidia.ml-1. The aqueous fraction was composed of 0.1% Geropon T36 compatibilizer, 0.075% silicone, the dispersant, 0.1% Tween 80 or tensioactive and 0.5% PVP K30 or spreading agent. The incidence of disease was observed in 83.6% of the plants inoculated with the formulated fungus, which was 79.0% higher than that in the plants inoculated with the bioagent only. These findings strongly suggest that the new formulation successfully controls Euphorbia heterophylla and greatly increases the pathogenicity of the fungus.   Key words: Bipolaris yamadae, Euphorbia heterophylla, adjuvants, biological control, phytopathogenic fungi.