Leaf Spot of Beach Morning-Gloryeach morning-glory (Ipomoea pes-caprae subsp. brasiliensis;...
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Plant Disease July 2013 PD- 95 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. Leaf Spot of Beach Morning-Glory Scot Nelson Department of Plant and Environmental Protection Sciences B each morning-glory ( Ipomoea pes-caprae subsp. brasiliensis; pöhuehue) is a hearty, vigorously creeping vine found just above the high-water mark on sandy Hawaiian beaches. Its thick green leaves are notched at the tips and resemble the impression of a goat’s foot ( pes-caprae ). Flowers are convex in shape and dusky pink (Neal 1991). The vine forms roots at the stem joints, which stabilize beach soils and minimize erosion by wind and water. Landscapers install beds of this ground-covering plant in commercial, residential, and resort landscapes in Hawai‘i. In early 2013, a landscaping contractor planted a large bed of beach morning-glory on the University of Hawai‘i at Mänoa campus. All of the plants displayed the typical symptoms and signs of a leaf spot disease common to this host throughout Hawai‘i. The disease is caused by species of the fungus Cercospora (Raabe et al. 1981). Here we discuss these plant pathogens, describe and illustrate the typical leaf spot symptoms, and suggest integrated management practices for reducing disease incidence and severity. Pathogens and Hosts • The following two species of Cercospora are known to cause leaf spot of beach morning-glory in Hawai‘i: Cercospora alabamensis G.F. Atk. (Stevens 1925), which infects beach morning-glory. • Cercospora ipomoea G. Winter (synonyms: Cerco- spora batatas and Cercospora bataticola ), which infects beach morning-glory and Ipomoea purpurea (purple, tall, or common morning-glory) (Raabe et al. 1981, Underwood 1897) . In 2003, C. ipomoea was re-named Passalora bataticola (Crous and Braun 2003).
Transcript of Leaf Spot of Beach Morning-Gloryeach morning-glory (Ipomoea pes-caprae subsp. brasiliensis;...
Plant DiseaseJuly 2013
PD- 95
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 US Department of Agriculture under the DirectorDean Cooperative Extension ServiceCTAHR University of Hawailsquoi at Mānoa Honolulu Hawailsquoi 96822 Copyright 2011 University of Hawailsquoi For reproduction and use permission contact the CTAHR Office of Communication Services ocsctahrhawaiiedu 808-956-7036 The university is an equal opportunityaffirmative action institution providing programs and services to the people of Hawailsquoi 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 wwwctahrhawaiiedufreepubs
Leaf Spot of Beach Morning-Glory
Scot NelsonDepartment of Plant and Environmental Protection Sciences
Beach morning-glory (Ipomoea pes-caprae subsp brasiliensis poumlhuehue) is a hearty vigorously
creeping vine found just above the high-water mark on sandy Hawaiian beaches Its thick green leaves are notched at the tips and resemble the impression of a goatrsquos foot (pes-caprae) Flowers are convex in shape and dusky pink (Neal 1991) The vine forms roots at the stem joints which stabilize beach soils and minimize erosion by wind and water Landscapers install beds of this ground-covering plant in commercial residential and resort landscapes in Hawailsquoi
In early 2013 a landscaping contractor planted a large bed of beach morning-glory on the University of Hawailsquoi at Maumlnoa campus All of the plants displayed the typical symptoms and signs of a leaf spot disease common to this host throughout Hawailsquoi The disease is caused by species of the fungus Cercospora (Raabe et
al 1981) Here we discuss these plant pathogens describe and illustrate the typical leaf spot symptoms and suggest integrated management practices for reducing disease incidence and severity
Pathogens and Hostsbull The following two species of Cercospora are known
to cause leaf spot of beach morning-glory in Hawailsquoi Cercospora alabamensis GF Atk (Stevens 1925) which infects beach morning-glory
bull Cercospora ipomoea G Winter (synonyms Cerco-spora batatas and Cercospora bataticola) which infects beach morning-glory and Ipomoea purpurea (purple tall or common morning-glory) (Raabe et al 1981 Underwood 1897) In 2003 C ipomoea was re-named Passalora bataticola (Crous and Braun 2003)
UHndashCTAHR Leaf Spot of Beach Morning-Glory PD-95 mdash July 2013
2
Disease SymptomsThese symptoms described below occur widely on beach morning-glory in Hawailsquoi However the incidence andseverityofsymptomsataspecificlocationmaybesporadic and weather-dependent Extended periods of rainfall and high humidity favor infection as well as disease development and spreadbull Leaf spots with tan centers and darkly colored
marginsapprox1minus4mmindiameternumerousscattered over leaf surface may coalesce to form blighted areas on leaves
bull Leaf yellowingbull Leaf curlingbull Premature leaf death and defoliationbull Spots on petioles
Disease ManagementEffective management of the disease may be achieved through integrating the following practicesbull Sanitation Remove fallen symptomatic leaves from
the area as the pathogen can survive on dead leaf tissue
bull Increase air movement in the canopy by removing and destroying heavily symptomatic leaves Thin out the plant canopy to improve aeration and promote drying of the leaves Avoid growing beach morning-glory near windbreaks that prevent the leaves from drying rapidly after rainfall
bull Avoid irrigating plants with overhead sprinklers especially in plant nurseries
bull Keep plants well fertilized Diseases caused by Cercospora species often develop more rapidly and are more severe in plants lacking essential elements especially nitrogen and potassium
bull In landscapes intercrop beach morning glory with other non-susceptible ground covers such as ilima (Sida fallax)
bull Grow plants in full sunlight rather than shadebull Avoid using symptomatic plants in landscapes where
the disease is not present
AcknowledgementsThe author thanks Fred Brooks (UH-CTAHR) and For-est Starr (UH-PCSU) for their thoughtful reviews of this manuscript
ReferencesNeal MC 1991 In Gardens of Hawaii Bernice P Bishop
Museum Special Publication 50 Bishop Museum Press Honolulu HI
Raabe RD Conners IL and Martinez AP 1981 Check-list of Plant Diseases in Hawaii Including Records of Microorganisms Principally Fungi Found in the State Hawaii Institute of Tropical Agriculture and Human Resources College of Tropical Agriculture and Human Resources University of Hawailsquoi Infor-mation Text Series 022
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UHndashCTAHR Leaf Spot of Beach Morning-Glory PD-95 mdash July 2013
Stevens FL 1925 Hawaiian fungi Bernice P Bishop Museum Bulletin 191ndash189 pl 1ndash10
Underwood LM 1897 A preliminary list of Alabama fungi Bulletin of the Alabama Agricultural Experi-ment Station 801ndash283 httpbooksgooglecombookshl=enamplr=ampid=KBMmAQAAMAAJampoi=fndamppg=PA111ampdq=22Cercospora+alabamensis22ampots=6csB7g0CFjampsig=9cE1Z4rCH52O4lQsUKRXx0sblgMv=onepageampq=22Cercospora20alabamensis22ampf=false
Wagner WL Herbst DR and Sohmer SH 1999 Manual of the Flowering Plants of Hawailsquoi University of Hawailsquoi Press Bishop Museum Press Honolulu HI
UHndashCTAHR Leaf Spot of Beach Morning-Glory PD-95 mdash July 2013
2
Disease SymptomsThese symptoms described below occur widely on beach morning-glory in Hawailsquoi However the incidence andseverityofsymptomsataspecificlocationmaybesporadic and weather-dependent Extended periods of rainfall and high humidity favor infection as well as disease development and spreadbull Leaf spots with tan centers and darkly colored
marginsapprox1minus4mmindiameternumerousscattered over leaf surface may coalesce to form blighted areas on leaves
bull Leaf yellowingbull Leaf curlingbull Premature leaf death and defoliationbull Spots on petioles
Disease ManagementEffective management of the disease may be achieved through integrating the following practicesbull Sanitation Remove fallen symptomatic leaves from
the area as the pathogen can survive on dead leaf tissue
bull Increase air movement in the canopy by removing and destroying heavily symptomatic leaves Thin out the plant canopy to improve aeration and promote drying of the leaves Avoid growing beach morning-glory near windbreaks that prevent the leaves from drying rapidly after rainfall
bull Avoid irrigating plants with overhead sprinklers especially in plant nurseries
bull Keep plants well fertilized Diseases caused by Cercospora species often develop more rapidly and are more severe in plants lacking essential elements especially nitrogen and potassium
bull In landscapes intercrop beach morning glory with other non-susceptible ground covers such as ilima (Sida fallax)
bull Grow plants in full sunlight rather than shadebull Avoid using symptomatic plants in landscapes where
the disease is not present
AcknowledgementsThe author thanks Fred Brooks (UH-CTAHR) and For-est Starr (UH-PCSU) for their thoughtful reviews of this manuscript
ReferencesNeal MC 1991 In Gardens of Hawaii Bernice P Bishop
Museum Special Publication 50 Bishop Museum Press Honolulu HI
Raabe RD Conners IL and Martinez AP 1981 Check-list of Plant Diseases in Hawaii Including Records of Microorganisms Principally Fungi Found in the State Hawaii Institute of Tropical Agriculture and Human Resources College of Tropical Agriculture and Human Resources University of Hawailsquoi Infor-mation Text Series 022
3
UHndashCTAHR Leaf Spot of Beach Morning-Glory PD-95 mdash July 2013
Stevens FL 1925 Hawaiian fungi Bernice P Bishop Museum Bulletin 191ndash189 pl 1ndash10
Underwood LM 1897 A preliminary list of Alabama fungi Bulletin of the Alabama Agricultural Experi-ment Station 801ndash283 httpbooksgooglecombookshl=enamplr=ampid=KBMmAQAAMAAJampoi=fndamppg=PA111ampdq=22Cercospora+alabamensis22ampots=6csB7g0CFjampsig=9cE1Z4rCH52O4lQsUKRXx0sblgMv=onepageampq=22Cercospora20alabamensis22ampf=false
Wagner WL Herbst DR and Sohmer SH 1999 Manual of the Flowering Plants of Hawailsquoi University of Hawailsquoi Press Bishop Museum Press Honolulu HI
3
UHndashCTAHR Leaf Spot of Beach Morning-Glory PD-95 mdash July 2013
Stevens FL 1925 Hawaiian fungi Bernice P Bishop Museum Bulletin 191ndash189 pl 1ndash10
Underwood LM 1897 A preliminary list of Alabama fungi Bulletin of the Alabama Agricultural Experi-ment Station 801ndash283 httpbooksgooglecombookshl=enamplr=ampid=KBMmAQAAMAAJampoi=fndamppg=PA111ampdq=22Cercospora+alabamensis22ampots=6csB7g0CFjampsig=9cE1Z4rCH52O4lQsUKRXx0sblgMv=onepageampq=22Cercospora20alabamensis22ampf=false
Wagner WL Herbst DR and Sohmer SH 1999 Manual of the Flowering Plants of Hawailsquoi University of Hawailsquoi Press Bishop Museum Press Honolulu HI
