There is disclosed a method and composition for controlling rust disease in plants. Metabolites produced by Aphanocladium album mycoparasites are recovered and applied in an effective amount to plants at risk for acquiring rust disease More specifically, the application of the metabolite converts infective urediniospores that cause rust disease into non-infective teliospores. In a more specific aspect, the metabolite is reacted with another substance or under a specific reaction to result in a different compound which is also effective against rust disease.
