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  1. 1. Carnation (Dianthus) Diseases Gary W. Moorman, Professor of Plant Pathology Disease Symptoms ALTERNARIA LEAF SPOT Small purplish spots form on leaves. Their centers become brown while the leaf yellows. BACTERIAL SLOW WILT OR STUNT Wilting, twisting, curling and stunting of lower leaves and side shoots followed by death of lower leaves. Wilted plants may recover only to wilt again. Stunted plants have narrow, yellow-green leaves. Symptoms require several weeks to develop. BACTERIAL WILT Leaves turn gray-green then yellow and die. Roots rot. Vascular tissue browns.Cracksdevelop in internode tissue. Slime oozes from these cracks when humidity is high. Pathogen/Cause Management Alternariadianthicola or Alternariadianthi Apply chlorothalonil, propiconazole, fludioxonil, copper hydroxide, iprodione, mancozeb, or mancozeb + thiophanate methyl to protect healthy plants. Erwiniachrysanthemi Grow in raised beds pasteurized between crops. Use culture indexed cuttings free of the pathogen. Destroy infected plants. Pseudomonas caryophylli Pot and propagate in pasteurized raised beds. Use clean, disinfested tools. Use cultureindexed cuttings free of the pathogen. Destroy infected plants. Botrytis cinerea Space plants to insure good air circulation. Maintain low humidity. Avoid watering late in the day. Remove crop debris. Apply chlorothalonil, cupric hydroxide, iprodione, mancozeb, or fludioxonil. BOTRYTIS BLIGHT Petals turn brown and are covered with gray, fungal growth. FUSARIUM WILT Lower leaves yellow and wilt up one side of plant. Symptoms progress up plant. Top of main shoot grows at right angle to main stem. Late in the disease, root and stems rot. Fusariumoxysporum Pot and propagate in pasteurized raised benches. Use culture indexed plants free of the pathogen. FUSARIUM STEM ROT Reddish-brown spots at the base. No vascular discoloration occurs beyond the rotted area. Fusariumgraminearum, F. avenaceum, or F. culmorum Plant only healthy, pathogen-free cuttings in pasteurized, raised beds. GREASY BLOTCH Small, web-like patterns give leaves a greasy appearance. Leaves yellow and die. Zygophialajamaicensis Maintain relative humidity below 85%.
  2. 2. PHIALOPHORA WILT Plants wilt, leaves yellow, and vascular tissue is discolored dark brown. Phialophoracinerescens See Fusarium wilt above. RHIZOCTONIA STEM ROT Stems at the soil level have a lesion with a brown border. Stems have dry shredded appearance. Rhizoctoniasolani Plant in pasteurized, raised beds. Apply thiophanate methyl, PCNB or iprodione as a soil drench to protect healthy plants. RUST Small blisters containing rust-red spores form on leaves. Uromycesdianthi Apply chlorothalonil, propiconazole, myclobutanil, ziram, mancozeb + thiophanate methyl, triadimefon, or triforine to protect healthy plants. VIRUSES Leaves may be mottled, have yellow spotting, dead flecks, line or ring spot patterns. Plant may be distorted or have flower color breaking. 15 different viruses are known. Plant virus-indexed cuttings. Maintain good insect and mite control. Destroy infected plants. Alternaria leaf spot.Anthurium Diseases: Identification and Control in Commercial Greenhouse Operations1 David J. Norman and Gul Shad Ali 2 Introduction Because of its attractive, long-lasting flowers, Anthurium is popular as both an exotic cut-flower crop and as a flowering potted-plant crop. Growers most often report two bacterial diseases and three fungal diseases in their
  3. 3. commercial greenhouse environments. This article provides guidelines to identify and treat diseases that may be encountered during commercial greenhouse production of Anthurium. Anthurium Commonly known as flamingo flower, Hawaiian love plant, cresta de gallo, or tongue of fire, Anthurium has nearly 1,000 species, making it the largest genus in the plant family Araceae. Anthurium is native to tropical America, Mexico, Costa Rica, Cuba, and Brazil. Growth habits vary depending on species; some are terrestrial, others are epiphytic (Chen et al. 2003). Most cut-flower Anthurium cultivars are selections of Anthuriumandraeanum, an epiphytic-growing plant native to Columbia and Ecuador. The large red flowers produced by Anthuriumandraeanum cultivars are very recognizable to consumers (Figure 1). Breeding has introduced such flower colors as pink, orange, white, green, purple, and combinations of these colors. Figure 1. Anthurium 'Kozohara' used in cut-flower production Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Florida is now leading the nation in flowering potted Anthurium production. Cultivars for potted plant production have been derived from crosses of A. andraeanum with dwarf species, such as A. amnicola and A. antioquiense. Compact, hybrid varieties of potted Anthuriumreleased by the University of Florida Plant Breeding Program include 'Red Hot' (Henny, Chen, and Mellich 2008a), 'Orange Hot' (Figure 2) (Henny, Chen, and Mellich 2008b), and 'Southern Blush' (Henny, Poole, and Conover 1988).
  4. 4. Figure 2. Anthurium 'Orange Hot' used in flowering potted plant production Credit: R. J. Henny, UF/IFAS [Click thumbnail to enlarge.] Anthurium is very susceptible to bacterial and fungal diseases that can seriously limit commercial production. Bacterial blight caused byXanthomonas is probably the most serious. Root rots caused by Rhizoctonia, Pythium, and Phytophthora also occur in Anthuriumproduction. It is therefore important to be able to identify and eliminate these diseases. Bacterial Diseases of Anthurium Bacterial Blight Figure 3. Xanthomonas bacterial blight exhibits characteristic V-shaped, water-soaked lesions forming along the edges on Anthuriumleaves. Credit: D. Norman, UF/IFAS
  5. 5. [Click thumbnail to enlarge.] Symptoms: The first visible symptoms are yellowed (chlorotic), water-soaked lesions along the leaf margins that grow rapidly to form dead (necrotic) V-shaped lesions characteristic of this disease (Figure 3). The bacteria infect Anthurium plants by entering pores (hydathodes) along the leaf margins (Figure 4). Bacteria may also enter if leaf tissues become torn through pruning, or if leaf tissues are punctured by insects. When flowers are harvested, bacteria can enter via wounds. Figure 4. Xanthomonas bacteria enter the leaf margins via pores (hydathodes) where guttation droplets form. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Figure 5. Extensive necrosis develops on Anthurium plants that are systemically infected with Xanthomonas bacterial blight. Credit: D. Norman, UF/IFAS
  6. 6. [Click thumbnail to enlarge.] Guttation droplets form at night when humidity is high and potting soil is warm and wet. Amino acids found in this guttation fluid are a source of food for the invading bacteria. Some infected plants are asymptomatic (do not show any disease symptoms) for months as the bacteria multiply. Bacteria in the guttation fluid from these asymptomatic infected plants can infect adjacent plants. Invading bacteria quickly spread throughout the plant (Figure 5). Leaves of systemically infected plants may exhibit a bronzed appearance. Floral quality may be reduced and/or flowers may become unmarketable (Figure 6). Eventually, plants wilt and die. Figure 6. Xanthomonas bacterial blight lesions can also appear on the flowers. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Causal Agent: Xanthomonasaxonopodis pv. dieffenbachiae The species of Xanthomonas that infects Anthurium has a very broad host range and is able to infect most aroid species; therefore,Anthurium plants may get blight when grown in close proximity to other aroids, such as Dieffenbachia, Aglaonema, and Spathiphyllum. Factors Favoring the Disease: Bacteria can swim across wet surfaces; therefore, it is very important to keep the foliage dry. The most effective way of accomplishing this is through drip irrigation. Control and Treatment: Lower greenhouse humidity and temperature by increasing air circulation and venting the production facility. Allow space between the plants on the bench. Warm temperatures, high humidity, and saturated soils contribute to the formation of guttation droplets.
  7. 7. Only clean, tissue-cultured plantlets should be used when establishing new plantings. Because Xanthomonas bacteria can enter the plant through any wound or tear in the stem or foliage, the disease is easily spread if propagation is done via cuttings or division. The disease can be spread when harvesting flowers or removing old foliage. Sterilize knives and clippers by dipping cutting tools in a disinfectant between plants. The most effective disinfectants are the quaternary ammonium compounds. It is also good practice to have two knives or shears in a dip bucket so they can be alternated, thus extending time in disinfectant and allowing for better coverage of the cutting surface. When infected plants are found, they should be discarded immediately. Products containing copper (CuPro, Phyton 27®, Camelot), mancozeb (Protect T/O™, Dithane®), and Bacillus subtilis (Cease®, Companion®) are effective against Xanthomonas. Bacterial Wilt Figure 7. Ralstonia bacterial wilt causes yellowing (chlorosis) of Anthurium leaves. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Symptoms: Leaf yellowing (chlorosis) is usually the first symptom observed. The disease spreads rapidly throughout the vascular system of the plant, turning veins in the leaves and stems a brown, bronze color (Figure 8). Bacterial ooze (brown slime) will be present if cuts are made into the stems of highly infected plants. Plants will exhibit wilt symptoms even though adequate soil moisture is available.
  8. 8. Figure 8. Wilt symptoms are the byproduct of Ralstonia bacteria clogging the vascular system of the plant. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Causal Agent: Ralstoniasolanacearum Ralstonia is known to infect several hundred plant genera. This bacterial disease is an opportunistic pathogen that colonizes soil and can remain viable for years without a host plant. Factors Favoring the Disease: Cool greenhouse temperatures may temporarily mask symptoms and give bacteria time to spread. Symptoms appear rapidly during hot weather. Control and Treatment: A strict sanitation program is the most successful way to stop the spread of this pathogen and eventually eradicate it from a production facility. Fungicides that contain phosphorous acid have also been shown to be effective in preventing infection; however, they do not cure systemically infected plants (Norman et al. 2006). Bacterial wilt is spread via contaminated soil, water, tools, or worker contact. Use disease-free propagation material. The bacterial wilt pathogen is easily spread via infected cuttings. Because the bacteria survive well in soil, both contaminated plant material and the supporting soil should be discarded. If pots and trays from contaminated infected plants are to be reused, they should be scrubbed free of adhering soil and then soaked in a disinfectant to kill the remaining bacteria. Knives and clippers should be sterilized between plants with a disinfectant containing a quaternary ammonium compound (Physan 20™, Green-Shield®) or diluted solution of bleach to prohibit spread. Fungal Diseases of Anthurium Rhizoctonia Root Rot
  9. 9. Figure 9. Anthurium wilt caused by Rhizoctonia root rot. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Symptoms: The term "damping-off" is used to describe these classical symptoms. Young, tender stems are girdled, become water soaked, and are unable to support the weight of the plant (Figure 9). Rhizoctonia attacks the roots and lower stems of plants (Figure 10), but under wet conditions it can also attack and spread in the upper leaf canopy. Figure 10. Discolored brown roots are one of the symptoms observed with Rhizoctonia infections. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Causal Agent: Rhizoctoniasolani
  10. 10. Rhizoctonia can survive within soil for years without a host plant. The fungus produces small mats of tightly woven mycelia called sclerotia. Sclerotia are irregular in shape, brown in color, and resemble particles of soil. Sclerotia provide a seedlike mechanism for the fungus to survive unfavorable conditions, such as drought or cold weather. These small sclerotia stick to trays and pot surfaces and are one of the ways the fungus spreads through nurseries. Factors Favoring the Disease: Water-saturated soils are conducive to disease development. Control and Treatment: Never incorporate native soils into media mixes without steam sterilizing. Use well-drained soil mixes. Never store peat moss, sphagnum moss, chips, or potting media mixes directly on soil surfaces where they can be colonized by the fungus. Plants should be cultivated on raised benches to limit root contact with soil. Rhizoctonia frequently gains access to production facilities via infected propagation material. Many fungicides are effective against outbreaks of Rhizoctonia. Examples include Clearys 3336®, Fungo®/Allban™ (thiophanate methyl), Medallion® (fludioxonil), and Contrast® (flutolanil). Phytophthora/Pythium Figure 11. Anthurium wilt caused by Phytophthora. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Both Phytophthora and Pythium are called "oomycetes," commonly known as water molds. The control, spread, and management recommendations for Phytophthora and Pythium infestations are the same. Plants infected with either of these pathogens exhibit wilting, leaf yellowing (chlorosis), and root dieback (Figure 11).
  11. 11. Figure 12. Pythium and Phytophthora cause root sloughing. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Symptoms: Phytophthora and Pythium infections primarily attack root systems. Plants will wilt even though adequate soil moisture is available. Root sloughing is the primary diagnostic tool (Figure 12). Under severe conditions, the foliage may exhibit black to brown leaf lesions. These symptoms are similar to symptoms caused by Rhizoctonia; however, fungal strands (mycelial growth) are rarely observed withPhytophthora or Pythium infections. Causal Agents: Phytophthoranicotianae var. parasitica and Pythiumsplendens Phytophthora and Pythium species cause substantial damage to Anthurium and numerous tropical foliage crops. Factors Favoring the Disease: Water-saturated soils are conducive to disease development. These diseases can usually be avoided by using light, well-drained soil mixes. Control and Treatment: Use well-drained, synthetic soil mixes. Use disease-free stock plants. Plants with symptoms of disease should be discarded and the rest of the production facility should be treated with a fungicide drench. If potting containers are reused, they should be scrubbed and sterilized. Cutting shears, knives, and tools should be dipped in an appropriate disinfectant between plants. Fungicides such as mefenoxam (Subdue® Maxx®) and aluminum tris/Fosetyl-al (Aliette® WDG), dimethomorph (Stature®), fluopicolide (Adorn™), and phosphorous acid (Alude™, K-Phite®, Vital®) may be used to control Phytophthora and Pythium. Black Nose Disease
  12. 12. Figure 13a. Black nose disease on Anthurium causes spadix darkening. Credit: D. Norman, UF/IFAS [Click thumbnail to enlarge.] Figure 13b. [Click thumbnail to enlarge.] Symptoms: Black nose can cause havoc in cut-flower and potted-plant production. Flowers and flowering potted plants cannot be sold with this condition. The first symptoms observed are small, brown to black flecks on the floral spadix (nose) (Figure 12). These spots rapidly enlarge, become watery, turn brown to black, and may totally encompass the spadix. The spadix may eventually fall off. Growers may also observe black, spore-containing structures (acervuli) on dead leaves and stems. Causal Agent: Colletotrichumgloeosporioides The fungus Colletotrichumgloeosporioides attacks many temperate and tropical crops and can cause damage to roots, stems, leaves, and flowers. However, in Anthurium the pathogen is highly specific, only attacking the spadix portion of the flower (the nose). Factors Favoring the Disease: This disease is most severe during humid, warm conditions. Colletotrichum readily invades plant tissues previously damaged by pesticides, fertilizer, or bacterial blight (Xanthomonas).
  13. 13. Control and Treatment: The Colletotrichum fungus produces thousands of small hot-dog-shaped spores that can readily be moved by splashing water, air movement, and workers. A strict sanitation program is crucial to control the spread of this pathogen in a production facility. Fungicides containing mancozeb (Protect T/O™, Dithane®) are effective. Fungicide applications are usually discouraged because chemical residues diminish the marketability of flowers and plants. Anthurium plant breeding programs both in Hawaii and Florida have incorporated disease resistance into many of the current cultivars. Newer cultivars are highly resistant to this pathogen and rarely exhibit black nose. References Chen, J., D. B. McConnell, R. J. Henny, and K. C. Everitt. 2003. Cultural Guidelines for Commercial Production of Interiorscape Anthurium. ENH956. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/EP159. Henny, R. J., J. Chen, and T. A. Mellich. 2008a. New Florida Foliage Plant Cultivar: 'Red Hot' Anthurium. ENH1009. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/EP363. Henny, R. J., J. Chen, and T. A. Mellich. 2008b. New Florida Foliage Plant Cultivar: 'Orange Hot' Anthurium. ENH1100. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/EP364. Henny, R. J., R. T. Poole, and C.A. Conover.1988."'Southern Blush' Anthurium." HortScience 23(5): 922–923. Norman, D. J., J. Chen, A. Mangravita-Nova, and J. M. F. Yuen. 2006. "Control of Bacterial Wilt of Geranium with Phosphorus Acid." Plant Dis. 90(6): 798–802. Footnotes 1. This document is PP292, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date March 2012. Visit the EDIS website at http://edis.ifas.ufl.edu. 2. David J. Norman, associate professor, and Gul Shad Ali, assistant professor, Plant Pathology Department, University of Florida Institute of Food and Agricultural Sciences, Mid-Florida Resesarch and Education Center, Apopka, FL 32703 The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.
  14. 14. Rust Fusarium wilt. Active Ingredients and Trade Names of the Chemicals FRAC Group No. Risk Level Class Active ingredient REI Restricted Entry Interval Trade names (EPA Reg. no.) 1 3 Benzimidazole thiophanate methyl 12 3336 (1001-69), OHP 6672 (51036-32959807), Fungo Flo (51036-329-59807), Systec 1998 (48234-12) 2 3 Dicarboximide iprodione 12 Chipco 26GT (100-1138), (51036-36159807) 3 2 Piperazine triforine 12 Triforine (241-355) Triazole propiconazole 24 Banner MAXX (100-741), Propiconazole (51036-403), Spectator (62719-346-10404), Kestrel (66222-41-81943)
  15. 15. triadimefon 12 Strike (3125-436), Bayleton (432-1360) myclobutanil 24 Systhane (707-253) 12 Phenylpyrol fludioxonil 12 Medallion (100-769) 14 1 "Aromatic hydrocarbon" PCNB 12 Revere (400-407-10404), Blocker (5481211), Terraclor (400-399), Defend (5481444-1001) 1 Chloronitrile chlorothalonil 48 Daconil (50534-9), ExothermTermil (70223) 12 M 2 Echo (60063-7), PathGuard (60063-7-499), Concorde (72167-24-1812), Pegasus (72167-24-1812) Copper, fixed Kocide (352-656), Champion (55146-1) mancozeb 24 Dithane (707-180), FORE (707-87), Pentathlon (1818-251) manganexe + zinc 1+M 48 Dithiocarbamate Combined products copper hydroxide 24 Protect T/O (1001-65) 1 thiophanate methyl + mancozeb Zyban (58185-31) Fungicides and Fungicide Resistance Management - Certain fungicides, usually systemic fungicides, are said to be 'at risk' to the development of resistance if they are used repeatedly. See the Risk Level in the above table (1 = low risk; 3 = high risk). The Fungicide Resistance Action Committee has developed a numbering system in which chemicals with the same FRAC Group number have the same mode of action (See http://www.frac.info/frac/index.htm ). It is recommended that chemicals at high
  16. 16. risk be used sparingly and in rotation or mixed with chemicals with different modes of actions (different FRAC number). DISCLAIMER Notice: The user of this information assumes all risks for personal injury or property damage. Warning! Pesticides are poisonous. Read and follow all directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams or ponds. Issued in furtherance of Cooperative Extension work, Acts of Congress, May 8 and June 30, 1914, in cooperation with the U. S. Department of Penn State College of Agricultural Sciences research and extension programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture. Visit Penn State Extension on the web at extension.psu.edu. Where trade names appear, no discrimination is intended, and no endorsement by Penn State Cooperative Extension is implied. This publication is available in alternative media on request. The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, gender identity, or veteran status. Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901; Tel 814-865-4700/V, 814-863-1150/TTY.