University of California

Olive leaf spot and its control with fungicides


E. E. Wilson
H. N. Miller

Authors Affiliations

E. E. Wilson was Professor of Plant Pathology and Plant Pathologist in the Experiment Station; H. N. Miller was Research Assistant in Plant Pathology.

Publication Information

Hilgardia 19(1):1-24. DOI:10.3733/hilg.v19n01p001. March 1949.

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In Brief

Olive leaf spot, caused by the fungus Cycloconium oleaginum Cast., has recently been prevalent in California. The first symptoms are inconspicuous sooty blotches on the leaf blade. As these enlarge, the rest of the leaf turns yellow. Severe defoliation follows leaf infection. In some orchards 10 to 20 per cent of the fruiting twigs died as a result of defoliation.

The fungus was isolated by transferring single ungerminated conidia to a solid medium. It proved to be extremely slow-growing. Only three of many isolates produced conidia in culture. Conidia germinated and mycelium grew between 9° and 30° C, the optimum being 16° to 20°.

New lesions developed in the fall one season in central California, but not until late January and February in three other seasons. Affected leaves became yellow and fell during May and early June.

Lesions on leaves that remained in the tree seem to be the chief if not the only source of inoculum. These bore numerous conidia in spring but few during the summer. In autumn the fungus grew from the margins of such lesions into adjacent leaf tissue and produced conidia; thus a supply of inoculum was insured at a time when moisture conditions were favorable to infection. The spores seem to be spread by rain more than by air currents.

Bordeaux mixture (8-8-100 or 10-10-100) applied in fall or early winter effectively prevented leaf infection in three out of four seasons. Later applications gave less satisfactory control. For two seasons one treatment of 8-8-100 bordeaux proved less efficacious than two treatments. In the next two seasons, however, one November treatment of 10-10-100 bordeaux gave adequate protection. On the whole, proper timing of the bordeaux treatment seemed more important than renewing the fungicide deposit.

Ferric dimethyl dithiocarbamate and zinc dimethyl dithiocarbamate sprays containing an oil supplement (“sticker”) reduced infection materially but not so effectively as bordeaux.

Yellow cuprous oxide in a two-treatment program reduced infection satisfactorily but injured the leaves.

Lime-sulfur (3 per cent) controlled leaf spot as effectively as 10-10-100 bordeaux.

Persistent effects of treatments were sometimes noted. In several orchards trees sprayed with bordeaux or lime-sulfur in only one season bore less leaf spot at the end of the next season than did unsprayed trees.

Literature Cited

Anagnostopoulos P. T. The Cycloconium of the olive in Greece. [Translated title.]. Hort. Res., Athens. 1937. 1937:357-67. Reviewed in: Rev. Appl. Mycol. 17:405; 1938

Anonymous. Legislative and administrative measures in Spain. Internatl. Bul. Pl. Prot. 1932. 6:164-67. Reviewed in: Rev. Appl. Mycol. 12 127; 1933

Anonymous. Principales enfermedades parasitarias que fueron objecto de consulto en el segundo semestre (Julio-Diciembre) de 1941. Sanid. Veg. Santiago, Bol. 1941. 1:52-55.

Bernès J. Les parasites de l’olivier au Congrès oléicola de Nice. Prog. Agr. et Vitic. 1923. 80:518-24.

Bioletti F. T., Colby Geo. E. Olives. California Agr. Exp. Sta. Bul. 1899. 123:1-34.

Boyer G. Recherches sur les maladies de l’olivier: le Cycloconium oleaginum. Montpellier École Natl. d’Agr. Ann. 1891. 6:248-54.

Brizi U. Concerning Cycloconium oleaginum. [Translated title.]. Staz. Sper. Agr. Italy. 1894. 26:227-231. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 6:62; 1894-95

Brizi U. Bird’s-eye of olives. [Translated title.]. Staz. Sper. Agr. Italy. 1899. 32:329-98. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 11 554; 1899-1900

Canonaco A. Contributo alla flora micologica dell’A.O.I. I. Micromiceti dell’Eritrea. II. Ustilaginee. Boll. Giard. Bot. Palermo. 1936. 14:1-28. Reviewed in: Rev. Appl. Mycol. 16: 279; 1937

Castagne L. Catalogue des plantes qui croissent naturallement aux environs des Marseilles 1845. p.220. Reviewed by Boyer (1891)

Foëx E. Quelques maladies crytogamiques de l’olivier. VI Cong. Internatl. d’Oléiculture. Compt. Rend. des Trav. [Nice]. 1924. 1923:179-209.

Giulivo G. Il vaiolo dell’olivo. Istria Agr. 1927. 7:229-30.

Gorter G. J. M. A. A leaf spot disease of the olive. Farming in So. Africa. 1943. 18:795-98.

Guozdenovic F. Report of the Agricultural Chemical Experiment Station in Spalato. [Translated title.]. Oestrr. Landw. Versuchsw. Ztsch. 1901. 4:254-72. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 13 661; 1901-02

Hansen H. N. The dual phenomenon in imperfect fungi. Mycologia. 1938. 30:442-55. DOI: 10.2307/3754469 [CrossRef]

Hansen H. N., Snyder W. C. The dual phenomenon and sex in Hypomyces solani f. cucurbitae. Amer. Jour. Bot. 1943. 30:419-22.

Hayne Arthur P. Olives and olive oils. California Agr. Exp. Sta. Rept. 1893. 1892-93:279-322. http://www.archive.org/details/investigationsof104hayn

Horne W. T. Some diseases of the olive in California. Olive Jour. 1 (February):. 1917. 4:10

Horne W. T., Essig E. O., Herms W. B. Plant disease and pest control. California Agr. Exp. Sta. Cir. 1923. 265:1-96. https://archive.org/details/handbookofplantd204smit

Marinangeli L. Note di olivicoltura. Di due parassiti dell’olivo contro i quali occore subitro agire. Il Coltivatore. 1928. 74:379-82. Reviewed in: Rev. Appl. Mycol. 7 653; 1928

Miège E. Observations sur quelques maladies des plantes cultivées au Maroc en 1921. Soc. de Path. Vég. France Bul. 1922. 9:108

Moniz da Maia R. Contribuição para o estudo da importância fitopatológica do Schizophyllum alneum (L.) Schroet., em Portugal. Agron. Rev. (Lisbon) 4th Ser. 1924. 1:20-22.

Nattrass R. M. Diseases of the olive. Cyprus Agr. Jour. 1935. 30:55-57.

Navarro L., Noriega E. Diseases of the olive. [Translated title.]. Prog. Agr. y Pecuario. 1909. 15:31-33. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 20 1140; 1908-09

Nicolas G., Aggéry Mlle. Un Cycloconium parasite de Phillyrea angustifolia. Soc. Myc. de France Bul. 1928. 44:301-3.

Petri D. L. Studi sulle malattie dell’olivo. III. Alcune ricerche sulla biologia del Cycloconium oleaginum Cast. [Roma] R. Staz. di Patol. Veg. Mem. 1913. pp.3-136. Tipografia Nazionale di G. Bertero E. C

Tobler O., Rossi-Ferrini U. The use of bordeaux mixture for the control of Cycloconium on the olive. [Translated title.]. R. Accad. Econ. Agr. dei Georg. Firenze. Atti (Series 3). 1906. 5:327-37. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 18 451; 1906-07

Vennuccini V. A leaf disease of olives. [Translated title.]. Ent. Agr. e Patol. Veg. Bol. 1898. 5:85-87. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 11 59; 1899-1900

Wilson E. E. The peacock leaf spot of olive trees. California Olive Indus. News. 1946. 1:4

Zacharewicz E. La fumagine de l’olives et le Cycloconium oleaginum. Prog. Agr. et Vitic. (Ed. l’Est). 1903a. 24:110-13. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 14 881; 1902-03

Zacharewicz E. The sooty mold of the olive. [Translated title.]. Bul. Agr. de Algérie et Tunisie Bul. 1903b. 9:179-86. Reviewed in: U.S. Off. Expt. Stas., Expt. Sta. Rec. 15 270; 1903-04

Wilson E, Miller H. 1949. Olive leaf spot and its control with fungicides. Hilgardia 19(1):1-24. DOI:10.3733/hilg.v19n01p001
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