In field tests on the control of black spot of roses juglone stood up well. No phytotoxic activity could be noted on the cutinized stem and leaf surfaces. On the variety George Ahrens, juglone gave equal control with 2½ times as much 325 mesh sulfur, the standard control for this disease.
SUMMARY
1. Under certain conditions walnut trees exhibit toxicity to those plants whose roots are in intimate contact with the roots of the walnut.
2. This toxicity is due to the action of juglone, the oxidized form of hydrojuglone, a non-toxic substance occurring in the inner bark and green husk of walnuts.
3. Juglone has been used in dermatology to cure various skin disorders including both bacterial and fungus diseases.
4. As a seed protectant, juglone is unsuitable because of its inherent toxicity to the non-cutinzed root surfaces.
5. Laboratory and field tests have shown juglone to be an excellent fungicide
LITERATURE CITED
1. Bernthsen, A. and A. Semper Ueber die Constitution des Juglons und seine Synthese aus Naphtalin. Ber. d. deutsch. Chem. Gesellsch. 20: 934-941. 1887.
2. Brissemoret et Michaud Sur une nouvelle classe de médicaments de la peau; les quinones peroxydes. Jour. pharm. et chim. 7e ser. 16:283-285. 1917.