Tropical Fruit Diseases
Transcript of Tropical Fruit Diseases
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Tropical Fruit Diseases
Dr. Lisa KeithResearch Plant Pathologist
Tropical Plant Genetic Resource Management UnitUSDA-ARS, PBARC
Tropical Fruit Growers ConferenceSeptember 30, 2006
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Tropical Fruit Diseases• Rambutan disease surveys were conducted and a variety
of fungal pathogens were isolated and identified as the causal agents of fruit and leaf lesions. Our overall goal is to gain a better understanding of what fungi affect rambutan fruit quality and determine if pathogen management practices can result in improved fruit quality. The fungi identified included Lasmenia, Colletotrichum, Phomopsis, Lasiodiplodia and Pestalotiopsis. Growth studies at a variety of temperatures were conducted to determine if certain temperatures could suppress disease. Disease incidence was compared for six rambutan varieties. Fungal isolates were also evaluated for sensitivity to fungicides registered for use in Hawaii.
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Tropical Fruit Diseases• Until recently, lychees in Hawaii were relatively free of
pre-harvest diseases affecting fruit or foliage. This research aims to benefit the lychee industry in Hawaii by establishing the extent of disease problems, raising awareness of the incidence and damage, and eventually evaluate some potential control measures. Since growers may be unaware of the symptoms of lychee diseases and consider them as an unspecified “blemish”, it was felt that growers would immediately benefit from accurate identification and early intervention.
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Rambutan – Nephelium lappaceum
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Common Field Symptoms
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Rambutan
Day 0 Day 7 Day 9
Disease progression of a natural field sample
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Rambutan – Main FungiArtificial inoculations showing symptoms
Phomopsis, 5 days
Pestalotiopsis, 7 days Colletotrichum, 5 days
Lasmenia, 7 days
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Lychee – Litchi chinensis
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Common Field Symptoms
20X lesionmagnification
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Common Field Symptoms
Kaimana
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Lychee – Koch’s Postulates
Kwai Mi Pink
Main fungi on lychee include Colletotrichum, Phomopsis, Lasiodiplodia, and Pestalotiopsis
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Lychee – Susceptibility Study
Kaimana/Kwai Mi Pink, Non-wounded/Wounded, 7 days
Colletotrichum Phomopsis
LasiodiplodiaPestalotiopsis
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Conclusions•Similar symptoms for numerous fungi
• Pathogens can affect several hosts
•Multiple factors contribute to the onset of disease
•Fungi were identified morphologically and molecularly
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Conclusions•Differences in growth depending on
temperature
•Trilogy does not appear effective for control of fungal pathogens on rambutan
•Differences in variety susceptibility
•Fungi can cause significant losses
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Goals/Impact• Characterize host-pathogen interactions
• Develop disease control methods
• Evaluate how pre-harvest practices affect post-harvest quality
• Additional fungicide trials; field trials
• Determine resistant varieties
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The Team