630 US ISSN 0271-9916 June 1989 RESEARCH EXTENSION SERIES 107 DISEASES AND PESTS OF CARNATION E. E. Trujillo, R. Shimabuku, C. Hashimoto, and T. M. Hori IllTAHR • COLLEGE OF TROPICAL AGRICULTURE AND HUMAN RESOURCES UNIVERSITY OF HAWAll The Library of Congress has catalogued this serial publication as follows: Research extension series / Hawaii Institute ofTropical Agri­ culture and Human Resources.--oOl--[Honolulu, Hawaii]: The Institute, [1980- v. : ill. ; 22 cm. Irregular. Title from cover. Separately catalogued and classified in LC before and including no. 044. ISSN 0271-9916 = Research extension series - Hawaii Institute of Tropical Agriculture and Human Resources. 1. Agriculture-Hawaii-Collected works. 2. Agricul­ ture-Research-Hawaii-Collected works. I. Hawaii Institute of Tropical Agriculture and Human Resources. II. Title: Research extension series - Hawaii Institute of Tropical Agriculture and Human Resources. S52.5R47 630'.5-dcI9 85-645281 AACR 2 MARC-S Library of Congress [8506] THE AUTHORS E. E. Trujillo is a plant pathologist, Department of Plant Pathology, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. R. Shimabuku is a research associate, Maui Branch Station, Kula. C. Hashimoto and T. M. Hori are extension agents, Maui County, Kahului. CONTENTS Page Pathogen-induced Diseases 1 Carnation' Rust 1 Alternaria Blight 1 Flower Blight 1 Botrytis Flower Blight 1 Septoria Leaf Spot 1 Rhizoctonia Stem Rot 1 Phytophthora Blight 2 Fusarium Stem Rot 2 Bacterial Leaf Spot 2 Root Knot 2 Nutritional Disorders 2 Nitrogen Deficiency and Excess 2 Phosphorus Deficiency 2 Potassium Deficiency 2 Calcium Deficiency 3 Boron Deficiency 3 Magnesium Deficiency 3 Insect Pests 3 Carnation Bud Mite 3 Spider Mites 3 Thrips 3 Cutworms 3 Management of Diseases and Pests 3 Soil-borne Diseases 3 Foliar and Flower Diseases 11 Nutritional Disorders 15 Insect Pests 15 Literature Cited 15 DISEASES AND PESTS OF CARNATION E. E. Trujillo, R. Shil11abuku, C. Hashil11oto, and T. M. Hort PATHOGEN-INDUCED DISEASES carnations in Hawaii. Symptoms of this disease appear as tan to dark brown lesions on sepals Carnation Rust and petals (Fig. 3). These lesions are covered Rust, caused by the fungus Uromyces caryo­ with dark brown powdery spores that are phyllinus (= U. dianthi) is the most common disseminated by wind and rain (11, 14). Because foliar disease of carnation in Hawaii. The first flower parts must be wet for at least eight hours symptoms on leaves, stems, or flower buds are before infections can occur, extended wet periods small, slightly raised blisters that eventually with light night rains favor outbreaks of this rupture, forming pustules filled with powdery disease. reddish-brown spores (Fig. 1). A yellow margin surrounds the pustules and, when infections are Botrytis Flower Blight severe, entire leaves turn yellow and die. Stems Botrytis flower blight is caused by the fungus may be girdled when several pustules develop Botrytis cinerea. This fungal disease appears as around the shoot, resulting in decreased flower tan to light brown soft rots on the petals of production and quality. Plants may be attacked flower buds and opened flowers. Affected petals at any stage of development. Spores of this soon become covered with the grayish growth of fungus are disseminated by wind, splashing the fungus filaments, which later are covered by water, or infected cuttings (12). Disease is a powdery mass of grayish spores (Fig. 4). The favored by cool nights alternating with warm disease usually occurs when the environment is humid days. This induces dew at night and the cool and damp at night, and warm with high formation of a film of water on the leaf surface. relative humidity in the daytime (12). Because rust spores require free water for nine to 12 hours on the plant surfaces to germinate and Septoria LeafSpot infect, this disease is most severe in open air Septoria leaf spot is caused by the fungus culture and in plastic film greenhouses, where Septoria dianthi. Symptoms on leaves and dew formation is common (1). stems appear as light brown spots with purple margins. Small black specks are present at the Alternaria Blight center of the spots. These are the spore­ Initial leaf symptoms of alternaria blight of producing structures of the fungus. Individual carnation, caused by the fungus Alternaria lesions may enlarge and coalesce with adjacent dianthi, are tiny purple dots (1/16 to 1/8 inch). lesions to cause death of the leaf. Dissemination When moist weather prevails, the spots enlarge, of the fungus is by windblown rain and developing into large lesions with a purple splashing water. High relative humidity favors margin and a yellow-green border surrounding a the development of the disease and production of gray-brown center covered with black spores spores (6). (Fig. 2). Several lesions may expand and coalesce to form large, irregular necrotic areas that Rhlzoctonla Stem Rot eventually kill the entire leaf. The branches are Rhizoctonia stem rot is caused by the soil­ most frequently infected at the nodes and borne fungus Rhizoctonia solani. The symptom branch base. These infection centers enlarge to on rooted cuttings is a moist grayish-black rot at form cankers, which eventually girdle the stem, the soil line, which causes the top of the plant to causing the branch to wilt and the girdled wilt and die (Fig. 5). On older plants the rot may portion to turn yellow and die (12). Spores of this extend a couple of inches above the soil line, fungus are disseminated by wind, rain, and inducing bark decay, which is easily rubbed off. infected cuttings. The pathogen needs free water Occasionally brown mycelial strands may be to germinate and infect the leaves and stem (3, seen on the surface of diseased tissue. The fungus 12). causing this disease in Kula, Maui, has been found to belong to a genetically distinct stock, Flower Blight known as anastomosis grouping AG2-2 (15). Alternaria flower blight caused by the fungus This pathogen apparently has been introduced Alternaria dianthicola is without doubt the in infected cuttings from the continental United most serious blossom disease of outdoor States (16). 1 Phythophthora Blight tend to coalesce. Several spots will cause the Phytophthora blight is caused by the soil­ death of the leaf. These symptoms usually occur borne fungus Phytophthora parasitica. On on the older leaves first and gradually spread carnations, symptom expression depends on upward on the plant (5, 6). infection site. Infections occurring on the basal portion of the stem cause a typical Wilting and Root Knot collapse of the stem or plant. The fungus may Root galls on carnation are caused by para­ also invade the stem at any point on the plant, sitic root nematodes, Meloidogyne spp. The most causing stem collapse and eventual death of the characteristic symptom of this disease is the branch. If the infection is on the upper leaves profuse root swellings that assume innumerable and stem, blighting occurs. The most common shapes. The microscopic eel-shaped larvae of the symptom of this disease, however, is a Wilting, nematode infect roots at the tip, where the tissue collapse, and bleaching of the tips of healthy is soft and cell division is occurring. When the shoots (Fig. 6), which resembles bromide toxic­ female nematode attaches her stylet to dividing !ty symptoms (8). This is a common disease of root cells during feeding, she introduces growth carnations grown in areas where soil tempera­ hormones that cause the root cells to divide tures rise above 25°C in the daytime. abnormally, followed by root swelling and development of typical root-knot galls that are Fusarium Stem Rot several times larger than normal roots (Fig. 11). Fusarium stem rot is caused by the soil­ Symptoms of nematode-infected plants are lack borne fungus Fusarium roseum f. sp. gram­ of Vigor, stunting, and pale green to yellow inearum. The fungus may attack the plant at all leaves that tend to wilt in warm weather (13). stages of development and does the most damage to cuttings during propagation and to young plants at transplanting (6, 7, 12). Symptoms on NUTRITIONAL DISORDERS rooted cuttings range from wilted cuttings with a severely reddish-brown crown rot to apparently Nitrogen Deficiency and Excess healthy cuttings with small internal, amber­ Nitrogen concentration close to 20 ppm in colored crown lesions (Fig. 7). The latter the soil solution is reqUired for good growth. diseased cuttings can not be detected Visually Nitrogen deficiency symptoms become visible at and when planted in the fumigated fields serve 10 ppm as a pale, yellowish-green coloration of as initial sources of inoculum. Young plants the entire plant. Leaves become narrow and with basal stem rot become ash green, wilt, and straight, flowers become small, and dieback of die (Fig. 8). Upon closer inspection of diseased basal leaves is noticeable. cuttings, reddish-brown lesions with pink or Excess nitrogen in the soil over 25 ppm orange spore masses are found in association induces a dark green coloration of the foliage. with the disease. Fusarium roseum is most Leaves become fleshy and curling is excessive. virulent when carnation plants are injured or High salt concentration in greenhouse carna­ when conditions are unfavorable for growth of tion beds due to excessive application of soluble the plant (9). Wounds produced during harvest, fertilizers can cause symptoms similar to nitro­ or when pinching or pruning buds and branches, gen deficiency. This can be corrected by heavy are ideal ports of entry for the fungus. The watering to dissolve salts and leach them from fungus grows down the stump, eventually invad­ the beds (2, 4). ing the main stem or side branches (Fig. 9) and causing them to wilt, turn yellow, and die (9, 12, Phosphorus Deficiency 14).