Nobiletin is main fungistat in tangerines resistant to mal secco.

A number of crystalline compounds isolated from peel of tangerines resistant to "mal secco" were characterized and tested for fungistatic activity toward Deuterophoma tracheiphila. Nobiletin exhibited strong fungistatic activity, tangeritin was weakly active, and hesperidin slightly stimulated fungal growth. Rough lemon seedlings, inoculated with the pathogenic fungus, rapidly developed the symptoms of mal secco, whereas continuous infusion of the inoculated seedlings with nobiletin solution largely prevented appearance of the disease.