While the important activity of chlorothalonil is limited to a handful of plant diseases, two of them, Septoria tritici blotch of wheat and Ramularia leaf spot of barley, are currently among the most economically destructive diseases of wheat and barley, respectively. This is the case across much of western Europe, including Ireland.

In addition to its excellent protective activity against these two diseases, as a multisite fungicide it has not succumbed to resistance and has therefore also been a key component in fungicide anti-resistance measures. And because the molecule has been available for almost six decades, it has been incorporated into a multitude of products and has been one of the most, if not the most, cost-effective fungicides for cereal disease control.