Carambola Diseases
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Algal leaf spot
Fig. 1
Algal leaf spot of avocado (Persea americana) in Hilo, Hawai‘i, caused by Cephaleuros virescens

Algal leaf spot
Fig. 2
Algal leaf spot

Algae leaf spot
Fig. 3
Algal leaf spot


Fungi and algae are responsible for the principal diseases affecting carambola production in Florida. The most recurrent and problematic diseases include anthracnose (Colletotrichum gloeosporioides/Glomerella cingulata) and decline (Pythium splendens). Algal spot (Cephaleuros virescens) may become prevalent in late summer through late winter. Other diseases that intermittently affect carambola production are sooty mold (Leptothyrium sp.) and leaf spot (Cercospora averrhoa, Corynespora cassiicola, Phomopsis sp., Gloesporium sp., Phyllosticta sp.). Leaf spotting is more common on stressed or nutritionally deficient trees and occurs on older leaves that normally abscise during the winter and early spring. 1



Algal Leaf Spot
(Fig. 1,2,3)

This alga commences colonization late in the summer and progresses through the winter months. Initially hard to visualize, green, grey-green, or rust colored leaf spots become raised and circular. Stems may develop cracks where infestation is high. The alga eventually produces "spores" - which are rust colored. 1
Reddish colored leaf spot diseases are caused by various fungi (Cercospora averrhoa, Corynespora cassiicola, Phomopsis sp., Gloesporium sp. and Phyllosticta sp.). Observations indicate that these leaf spot fungi are more common on environmentally stressed or nutritionally deficient trees and occur on older leaves that normally abscise (drop) during the winter and early spring.  No control is necessary for these leaf spotting fungi. 2

Further Reading
Cephaleuros Species, the Plant-Parasitic Green Algae from the University of Hawai'i pdf 6 pages



Anthracnose
(caused by Colletotrichum gloeosporioides/Glomerella cingulata)

Anthracnose can occur on all parts of the carambola tree. Leaf infection starts as light green lesions that enlarge into irregular brown areas, giving the leaf a scorched appearance. Infected leaves may abscise. Infections on flower panicles appear as small brown or black spots which enlarge and often coalesce to cause the death of the flower. Small fruit are rapidly invaded by the fungus once they become infected and will rot and mummify on the tree. On nearly mature or ripe fruit, the resultant lesion is small and relatively cosmetic with a shallow area of hardened tissue. 1
Ripe fruit that is injured may be attacked by the fruit-rotting fungus (Colletotrichum gloeosporioides), which causes anthracnose. A superficial blackish discoloration on fruit ("sooty mold") caused by Gloeodes pomigena may be found on fruit surfaces. Generally, no
control is warranted for these fruit diseases. 2

Further Reading
Anthracnose from the University of Florida pdf



Decline

(caused by Pythium splendens)

This fungus has recently been identified as the cause of a general tree decline. Signs of decline include loss of tree vigor, leaf drop and twig, shoot and root die-back. Trees also demonstrate reduced fruit production in terms of number and size. 1
For more information and control measures, consult your County Agricultural Extension Agent.



Further Reading

Growing Carambola in the Florida Home Landscape from the University of Florida pdf 8 pages

Bibliography

1 Mossler, Mark A. and Crane, Jonathan. "Florida Crop/Pest Management Profile: Carambola". edis.ifas.ufl.edu. One of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Sept. 2002. Reviewed July 2013. Web. 27 Dec. 2013.
2 Crane, Jonathan, H. "Carambola Growing in the Florida Home Landscape". edis.ifas.ufl.edu. This document is HS12, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Publication date April 1994. Revised May 2007. Reviewed July 2013. Web. 28 Jan. 2014.

Photographs

Fig. 1,2,3 Nelson, Scot. Algal leaf spot of avocado (Persea americana) in Hilo, Hawai‘i, caused by Cephaleuros virescens. Aug. 2008. ctahr.hawaii.edu. Web. 28 Jan. 2014.

Published 27 Dec. 2014 LR. Last Update 20 June 2016 LR
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