Anthracnose of pitahaya: a new disease on a new crop in South Florida

Aaron J. Palmateer, Randy C. Ploetz

Abstract


Vine-like, climbing cacti in the genera Hylocereus and Selenicereus produce fruit known variously as pitaya, pitahaya, dragonfruit or strawberry pear. Hylocereus undatus, a native of Mexico that produces red fruit, has recently become a commercial crop in South Florida. In December, 2004, a new disease was observed in a commercial planting in Miami-Dade County. Reddish-brown lesions with conspicuous chlorotic haloes developed on the ribs of vines, in particular where spines emerged from the rib edge. Eventually, lesions had white centers and coalesced to rot much of the vine column; in severe cases only the vascular column in the vine center remained unaffected. Salmon-colored spores and acervuli were observed in lesion centers. Disease samples were collected and tissue from lesion margins were surface disinfested and plated on one-half strength, acidified potato dextrose agar. The fungus Colletotrichum gloeosporioides (Penz.) Penz. & Sacc was isolated from all symptomatic plant tissues. Isolates produced abundant conidia in culture that were hyaline, straight, cylindrical, and averaged 14.7 m (range 12.5 to 17.5 m) by 5.0 m (range 3.8 to 7.5 m). Two isolates were shown, in repeated experiments, to cause the described disease, and Koch's postulates were completed with the re-isolation of isolates that were used to inoculate plants. To our knowledge this disease had not been reported previously on this crop.

Keywords


Hylocereus undatus; Colletotrichum gloeosporioides; vine cactus; Koch's postulates; ?rst disease report

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283