Bulgarian Journal of Agricultural Science, 16 (No 2) 2010, 220-226 Agricultural Academy EFFECT OF ZINC UNDECYLENATES ON PLANT PATHOGENIC FUNGI A. NIKOLOV and D. GANCHEV Agricultural University, Department of Agroecology, BG – 4000 Plovdiv, Bulgaria Abstract NIKOLOV, A. and D. GANCHEV, 2010. Effect of zinc undecylenates on plant pathogenic fungi. Bulg. J. Agric. Sci., 16: 220-226 The undecylenic acid (10-undecenoic acid), an eleven-carbon monounsaturated fatty acid is a naturally occur- ring fatty acid found in the castor oil bean (Ricinus communis) and as a product of human sweat glands. It is produced commercially through the vacuum distillation of castor bean oil and pyrolysis of ricinoleic acid (Perkins, 1927). Since 1949, the undecylenate salts have been used as yeast and mold inhibitors in the food industry, and in medicine as topical and systemic antifungals (Bourne, Ireland, Stanberry, Bernstein, 1999). Zinc undecylenate has been shown to be an effective antifungal agent and is the active ingredient in many topical over-the-counter antifungal preparations. Undecylenic acid has been shown to be approximately six times more effective in its antifungal action than caprylic acid. Undecylenate salts have been shown to possess as much as four times the fungicidal effect of undecylenic acid, and may be over 30 times more effective than caprylic acid. These agents have also been shown to be effective in helping to maintain a healthy balance of intestinal and vaginal flora (Chretien, Esswein, Sharpe, 1980). In the present investigation we conducted in vitro and in vivo trials with zinc salts of the undecylenic acid with plant pathogenic fungi. The observed results showed that these salts have a strong antifungal effect and can be very effective plant protection remedy. Key words: undecylenic acid, undecylenate salts, zinc undecylenate, plant pathogens, antifungal Introduction Undecylenic acid is a natural fungicide approved in many country of the world as medical remedy for different kind of skin disorders, including infections, itching, burning and irrigations (hemorrhoids). It also is used as remedy for psoriasis. However undecylenic acid and its zinc salts have as fungicidal as antibacte- rial and antiviral properties – can be used for treat- ment of herpes simplex virus. As product of human sweat glands the acid and its salts are practically non- toxic for humans and mammalians. Since 1949, the undecylenate salts have been used as yeast and mold inhibitors in the food industry, and in medicine as topi- cal and systemic antifungals (Bourne et al., 1999). Undecylenate salts have been shown to possess as much as four times the fungicidal effect of undecylenic acid, and may be over 30 times more effective than caprylic acid. These agents have also been shown to be effective in helping to maintain a healthy balance of intestinal and vaginal flora (Chretien et al., 1980). In the current research we conducted in vitro tri- als (germ tube inhibitions tests and radial growth as- says) with zinc undecylenate salts against different 220