Plant Disease April 2012 PD-82

Cercospora Leaf Spot of Eggplant

Shikha Srivastava and Scot Nelson Department of Plant and Environmental Protection Sciences

ggplant (Solanum melon- many globally renowned dishes gena) is a warm-season veg- such as the French ratatouille, etableE cultivated worldwide for its the Italian melanzane alla par- fleshy fruit. The name is believed migiana, and the Middle Eastern to reflect the early forms of the baba ghanuj. In Indian cuisines, fruits, which were small, white, eggplant is used in a variety of and resembled eggs (Hui 2006). ways ranging from curries to The plant belongs to the genus chutneys. Baigun bhurta is the Solanum within the family So- most popular eggplant dish of lanaceae. Varieties are grown India. Aside from being used both as perennial and annual as food, eggplant is also used in crops. The typical plant has a medicines in China, Southeast spiny stem bearing broad leaves Asia, and the Philippines (TNAU and white to purple flowers. The Agritech Portal 2008). China is fruits are generally dark purple the leading producer of eggplant in color and have a wide range of in the world, contributing around shapes and sizes. The eggplant 55% of the world’s output. Other is believed to be native to India, major producers are India (28% of the world’s production), Egypt, where it has long been cultivated Cercospora leaf spot on eggplant growing (Gastier 2000). It is widely used in Mänoa Valley, O‘ahu, Hawai‘i Turkey, and Japan (Raabe et al. in China, India, Japan, and many 1981). Mediterranean countries (Hui 2006). Eggplant was in- In Hawai‘i, eggplant is an important crop grown by troduced to American gardeners in 1806 and to Hawai‘i farmers and home gardeners. Three distinct varieties are in 1824 (Staples and Herbst 2005). Initially, the plants cultivated for food, while others are grown as ornamen- were grown as ornamentals by gardeners, but later, with tal plants. Fruit of the Japanese-type eggplant, which is the development of less bitter-tasting varieties, the fruit mostly preferred by Asian cooks, is elongated and dark was accepted widely as an edible vegetable. purple colored. The Italian-type eggplant fruit, also dark Eggplant has many properties that make it an integral purple, is large and oval-shaped, and the Thai-type fruit, part of a healthy diet. It is a rich source of dietary fiber, which is smaller and rounder, is green to white (Staples vitamins, potassium, and calcium; it also has low fat, zero and Herbst 2005). According to Hawai‘i Agriculture Sta- cholesterol, and a very low calorie content. Therefore, tistics data, eggplant was grown on over 70 acres of land eggplant is a preferred food among weight-conscious in 2009 and had an economic value of US$1.2 million consumers. It can be boiled, stir-fried, deep-fried, (USDA, National Agriculture Statistics Service 2011). steamed, roasted, or baked. Eggplant is a vital element in More than 10 genera of plant-pathogenic fungi infect

Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in co- operation with the U.S. Department of Agriculture, under the Director/Dean, Cooperative Extension Service/CTAHR, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i 96822. Copyright 2011, University of Hawai‘i. For reproduction and use permission, contact the CTAHR Office of Communication Services, [email protected], 808-956-7036. The university is an equal opportunity/affirmative action institution providing programs and services to the people of Hawai‘i without regard to race, sex, gender identity and expression, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or status as a covered veteran. Find CTAHR publications at www.ctahr.hawaii.edu/freepubs. UH–CTAHR Cercospora Leaf Spot of Eggplant PD-82 — Apr. 2012

In a typical garden plot in Hawai‘i, eggplant is one of The centers of lesions may fall out, creating a shot-hole many different plants. It is often grown in congested appearance. Adjacent lesions may coalesce to form areas conditions within a confined space. This creates the high of blighted tissue. relative humidity that favors infection of eggplant leaves by Cercospora melongenae. eggplant in Hawai‘i (Hawai‘i Host-Pathogen Database equipment or by people (Nelson 2008). Leaf wetness 2012), some of them causing severe diseases. One of the and high relative humidity favor infection and disease most common fungal diseases of eggplant in home and development. Symptoms appear on the older, lowest community gardens is Cercospora leaf spot. This disease leaves first, and if unchecked can move upwards and weakens plants and reduces yields by causing the pre- infect young leaves and stems. Severely infected leaves mature defoliation of infected leaves. In this article we curl and prematurely drop off the plant, often causing discuss the pathogen and disease symptoms and suggest a reduction in yield (Chupp 2006). The pathogen does integrated management practices that can help gardeners not infect eggplant fruits but does reduce the growth of realize better plant growth and higher yields. plants and thus reduce yield. Where the disease is severe, it can be fatal to plants. Pathogen and Disease Symptoms appear on the leaves, petioles, and A plant-pathogenic fungus, Cercospora melongenae, stems of eggplant. Initially, small, circular to oval chlo- causes Cercospora leaf spot of eggplant in Hawai‘i. The rotic spots appear that may develop angular or irregular genus Cercospora is a hyphomycete fungus comprised shapes. The spots on leaves can easily be confused with of many plant-pathogenic species. They produce leaf spots caused by a bacterial disease. On closer inspection, spot diseases on a wide range of agriculturally important however, the spots due to Cercospora show distinguish- plants. These diseases are major problems for large-scale ing features. They are generally circular with light to dark growers and backyard gardeners (Chupp 1953; Farr 1989; tan centers, and the stomata have black spots that can Kranz and Werner 1978; TNAU Agritech Portal 1989; be readily observed using a hand-held magnifying lens. Gonsalves et al. 1994). There are about 1,200 known Elliptical to oval lesions may occur on the leaf blades, species in the genus Cercospora, with over 69 species veins, and petioles. Bacterial leaf spots, conversely, are reported in Hawai‘i (Raabe et al. 1981). irregularly shaped or circular spots with clear stomata Cercospora melongenae can survive for at least one (Windels et al. 2003). year in plant debris or in soil. The disease process be- The leaf spots on eggplant caused by C. melongenae gins when the fungal spores are dispersed to susceptible are 4–10 mm in diameter and visible on both leaf sur- plants by rain, irrigation water, or wind, or on agriculture faces, though they may appear more abundantly on the

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Lesions tend to appear first on older leaves. Infected leaves eventually turn yellow, curl up, and fall from the plant prematurely. lower surface. They are brown to steel-gray on the upper eggplant canopy. surface and light brown on the lower surface (Anony- • Irrigate in the morning to reduce humid and damp mous 2011). Conidiophores (fungal structures that bear conditions overnight. the spores/conidia) appear in fascicles (clusters) of 3 to • Avoid over-irrigation to reduce relative humidity. 12. They are pale to medium brown, paler towards the • Avoid overhead sprinkler irrigation in order to apex, occasionally septate, and unbranched, and they minimize leaf wetness and spread of the pathogen bear hyaline, mildly curved conidia (Mycobank Database in splashing water droplets. 2012). During the later stages of disease, lesions become • Do not work with wet plants or move through a grayish brown, with excessive sporulation at their centers. field of wet plants, as such movement can disperse Concentric rings of diseased tissue may appear as the fungal spores among plants. lesions gradually expand in size. As a lesion dries, the • Increase the spacing between plants to improve tissue in the center may crack and drop out. aeration and drying of wet foliage. • Keep plants adequately fertilized. Disease Management • Intercrop eggplant with other vegetables to interrupt Both organic and inorganic approaches can be used for pathogen transmission between plants. the management of this disease. • Grow eggplant under cover (i.e., in greehouses or • Maintain proper field sanitation: Collect and bury under shadecloth) where possible to minimize leaf infected crop residues; remove and destroy severely wetness. diseased leaves. • A calendar-based spray program using a protectant • Use disease-free transplants. fungicide, combined with cultural practices, can re- • Control weeds to reduce relative humidity in the duce losses from Cercospora leaf spot on eggplant.

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Table 1. Some fungicides registered in Hawai‘i for controlling Cercospora leaf spot disease of eggplant (Source: Hawai‘i Pesticide Information Retrieval System)

Active Ingredient(s) Product Name Formulation (Percent) Bravo Ultrex® Agricultural Chlorothalonil (82.5%) Water-dispersible granules Fungicide Bravo Weather Stik® Agricultural Chlorothalonil (54%) Emulsifiable concentrate Fungicide Bonide Liquid Copper Fungicide Octanoic acid, copper salt Flowable concentrate Concentrate (10%) Bonide Liquid Copper Fungicide Octanoic acid, copper salt Solution – ready to use Ready to Use (.08%) Bonide Neem Oil Fungicide · Clarified hydrophobic neem oil Oils – no added pesticide Miticide · Insecticide Concentrate (70%) Garden Safe® Brand Neem Oil Clarified hydrophobic neem oil Oils – no added pesticide Extract Concentrate (70%) Clarified hydrophobic neem oil Natural Guard® Neem Oils – no added pesticide (70%) Natural Guard® Copper Soap Octanoic acid, copper salt Flowable concentrate Liquid Fungicide (10%) Serenade® Garden Disease QST 713 strain of Bacillus Emulsifiable concentrate Control Concentrate subtilis (1.34%) Serenade® Garden Disease QST 713 strain of Bacillus Emulsifiable concentrate Control Ready to Spray subtilis (1.34%)

Acknowledgements html (accessed 28 February 2012) The authors thank Fred Brooks and Ty McDonald of UH- Gonsalves, AK, and Ferreira, S. 1994. Cercospora CTAHR for their thoughtful reviews of this manuscript. primer. http://www.extento.hawaii.edu/kbase/crop/ Type/cer_prim.htm - DISEASES (accessed 28 Feb- References ruary 2012). Anonymous. 2011. Small fruit and vegetable IPM ad- Hui, YH. 2006. Handbook of Food Science, Technology visory – Integrated pest management, Utah State and Engineering. CRC Press. p. 13-20 University Cooperative Extension Web portal. http:// Kranz, JS, and Werner K. 1978. Diseases, Pests and utahpests.usu.edu/ipm/htm/advisories/small-fruit- Weeds in Tropical Crops. Wiley Publications. pp. and-vegetable-advisory/articleID=13472 - leafspot 194-195. (accessed 28 February 2012). Mycobank Database. 2012. http://www.mycobank.org/ Chupp, C. 2006. Manual of Vegetable Plant Diseases, MycoTaxo.aspx?Link=T&Rec=270921(accessed 28 Discovery Publishing House, India. February 2012). Chupp, C. 1953. A Monograph of the Fungus Genus Nelson, SC. 2008. Cercospora leaf spot and berry blotch Cercospora. Cornell Univ., Ithaca, New York. of coffee. University of Hawai‘i, CTAHR Coopera- Farr, DF, Bills, GF, Chamuris, GP, and Rossman, AY. tive Extension Service. 1989. Fungi on Plants and Plant Products in the Nelson, S, and Bushe, B. 2012. Hawaii Host-Pathogen United States. APS Press, St. Paul, Minnesota. Database. http://hawaiiplantdisease.net/qd/index.ph Gastier, TW. 2000. Ohio State University Extension Fact p?path=HawaiiHostPathogenDatabase (accessed 9 Sheet. http://ohioline.osu.edu/hyg-fact/1000/1609. March 2012).

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Raabe, RD, Conners, IL, and Martinez, AP. 1981. Check- TNAU Agritech Portal. 2008. http://www.agritech.ac.in/ list of Plant Diseases in Hawaii. Hawaii Institute of org_farm/orgfarm_hortidiseases.html (accessed 28 Agriculture and Human Resources, College of Tropi- February 2012). cal Agriculture and Human Resources, University of United States Department of Agriculture, National Hawai‘i (Information Text Series 022). Agriculture Statistics Service. 2011. Statistics of Staples, GW, and Herbst, DR. (2005). A Tropical Gar- Hawaii Agriculture. http://www.nass.usda.gov/Statis- den Flora, Plants Cultivated in Hawaiian Islands tics_by_State/Hawaii (accessed 28 February 2012). and Other Tropical Places. Bishop Museum Press, Windels, CE, Bradley, CA, and Khan, MFR. 2003. Cer- Honolulu, Hawai‘i. cospora and bacterial leaf spots on sugarbeet. http:// The Hawaii Pesticide Information Retrieval System www.ag.ndsu.edu/pubs/plantsci/rowcrops/pp1244. (HPIRS) database http://state.ceris.purdue.edu/doc/ pdf (accessed 28 February 2012). hi/statehi.html (accessed 28 February 2012).

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