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Home HortScience Rambutan Fungal Attackers Revealed
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HILO, HI -- Rambutan is a tropical tree prized throughout Southeast Asia for its delicious fruit. Native to Malaysia and Indonesia, the colorful, thorny fruit is fast becoming significant in Hawaii's commercial exotic fruit industry. A challenge for the burgeoning market is rambutan fruit's extremely short shelf life, a result of diseases that are most often caused by fungal pathogens.

To help Hawaii's specialty fruit industry create a viable niche for rambutan fruit, researchers from the United States Department of Agriculture–Agricultural Research Service (USDA–-ARS) in Hilo looked to identify and understand the fruit's fungal attackers. The results of their rambutan research were published in HortScience.

To determine the main fungal pathogens affecting preharvest fruit quality, the scientists conducted a survey of rambutan disease orchards near Hilo. Four pathogens (Lasmenia, Pestalotiopsis, Phomopsis, and Colletotrichum spp.) were identified as the main fungal causes of fruit rot on rambutan. Over the 2-year sampling period, disease incidence from more than 300 fruits sampled was 84.6%. The researchers found that symptoms were similar for all four pathogens; tiny brown to black spots on the spinterns or on the rind of the fruit expanded over time and resulted in a dried out or crusty-looking appearance.

The fungicides Abound® and Triology® were evaluated for their effectiveness with the primary pathogens. Abound® was found to be more effective at inhibiting fungal growth than was Trilogy®; however, efficacy appeared to be influenced by fungal genera. The authors recommended additional field studies to determine if additional fungicides currently registered for use in Hawaii can help control pre- and/or postharvest fruit rot caused by the four fungal pathogens identified.

The scientists advised commercial growers to adopt proper management practices such as a program of field spraying, postharvest fungicide applications, and careful handling practices to help to minimize the development of fruit rots in rambutan. They added that spraying with the appropriate fungicides must begin at flower set and continue until harvest.

"Superior fruit quality is necessary for rambutan to have a competitive advantage in Hawaii," the report said. "To develop an integrated system of preharvest and postharvest practices that enable specialty tropical fruit growers to manage diseases, improve fruit quality, and extend shelf life, the economically important fungal pathogens must be identified and understood, and control measures must be developed."

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The complete study and abstract are available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/46/5/730

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org


 

Original Article:

Field Survey and Fungicide Screening of Fungal Pathogens of Rambutan (Nephelium lappaceum) Fruit Rot in Hawaii
Lisa Keith, Tracie Matsumoto, Kate Nishijima, Marisa Wall, and Mike Nagao
HortScience 46:730–735. [Abstract][Full Text][PDF]

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