Efficacy of plant oils on the control of bean rust and wheat leaf rust

Abstract

Bean rust, caused by the fungus Uromyces appendiculatus (Pers.:Pers.) Unger, and wheat leaf rust, caused by the fungus Puccinia triticina Eriks., are economically important foliar diseases and have global significance. The efficacy of eight plant oils (castor, corn, cottonseed, linseed, olive, peanut, soybean and sunflower seed oils) was evaluated as possible alternatives to synthetic fungicides for the control of U. appendiculatus and P. triticina in this study. The percentage of inhibition in urediniospore germination of all tested plant oils ranged from 0 to 100% and 0 to 84.9% against U appendiculatus and P. triticina, respectively. Among these plant oils tested, linseed oil was the most effective on the control of U appendiculatus and P. triticina in both in vitro and pot experiments. It completely inhibited the germination of the urediniospores of U appendiculatus at the highest concentration (2.5%) tested. At the same concentration, linseed oil inhibited by 84.9% the germination of the urediniospores of P. triticina. In pot experiments, control efficacy of all tested plant oils ranged from 0 to 95.2% and 17.8 to 100% against U appendiculatus and P. triticina, respectively. Linseed oil provided 95.2 and 100% control values at 1% concentration against U appendiculatus and P. triticina, respectively. All tested plant oils were found significantly effective in reducing pustules caused by P. triticina at all concentrations tested. Post-infection treatment of linseed oil was ineffective on the control of both U. appendiculatus and P. triticina. In the tests for the inhibition of urediniospore germination as well as reduction in the formation of uredinia (pustules) of both rust species there was an increase in the efficacy of the tested oils as the concentration of the oils increased. None of the tested plant oils were phytotoxic to bean and wheat leaves. The results of this study indicate that tested plant oils could become natural alternatives to synthetic fungicides for the control of tested rust fungi.