Polyoxins are antifungal antibiotics produced by Streptomycetes that were discovered through programs searching for new fungicides and insecticides for agricultural use. The polyoxins, first reported in the 1960s, were isolated from Streptomyces cacaoi. As inhibitors of chitin synthetase, they exhibit antifungal activity, but lack antibacterial activity. Since they also lack mammalian toxicity, they represent potentially useful models for the development of effective agents for the treatment of opportunistic fungal infections.The inhibitory effectiveness of polyoxin B (Polar) makes it a good candidate for the control of powdery mildews on grapevines, apple, and especially on nectarine trees. Polyoxin B is a chitin synthase (CHS) inhibitor with IC50 of 0.16 mM.