|ZEUTSA, E.H. MOMO|
|AMOUGOU, F. NSOUGA|
Submitted to: New Disease Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2007
Publication Date: 8/27/2007
Citation: Mbenoun, M., Zeutsa, E., Samuels, G.J., Amougou, F., Nyasse, S. 2007. Dieback due to Lasiodiplodia theobromae, a new phytosanitary constraint to cocoa culture in Cameroon. New Disease Reports. 15. Available: http://www.bspp.org.uk/ndr/july2007/2007-65.asp.
Interpretive Summary: Grown in tropical regions, cocoa is the major ingredient in chocolate, an important industry in the United States. Recently a mysterious dieback disease was discovered on cacao plants growing in Cameroon, a major cacao-producing country. In this paper the new dieback disease is described. The cause of the disease was determined to be a pathogenic fungus that occurs on many woody host plants throughout the tropics. Knowing what causes this disease will allow plant pathologists to develop control measure for this new dieback of cacao.
Technical Abstract: Since the introduction of cocoa (Theobroma cacao L.) in Cameroon in 1886, the only serious disease has been Phytophthora pod rot. Recently, cocoa orchards have been subjected to an increasingly important decline due to an uncommon dieback disease. Irrespective of age, affected cocoa trees manifest the typical symptoms of die-back. Leaves on the ultimate twigs first yellow the damage then may extend inwards over the whole branch, reaching the main stem and eventually resulting in tree mortality. The twigs and branches of diseased trees show internal discoloration with brown streaks scattered in the vascular tissue, and white or yellowish exudate from trunks has also been reported in certain locations. Although sudden global wilting and death may occur, more typically affected trees decline over several-months, during which time chupon sprouting may be induced at the collar of declining trees. Desiccated leaves and mummified fruits remain attached on such dried out trees for several weeks. Although tree mortality occurs throughout the year, the disease is more severe during the dry season, especially for trees under no or slight shade. Isolation of potential associated pathogens indicated that Lasiodiplodia theobromae is species most commonly associated with the die-back. This fungus was consistently isolated from various organs of symptomatic plants and re-isolated from infected plants. Lasiodiplodia theobromae is a common, widespread pathogen of tropical woody trees, causing shoot blight and dieback of trees and shrubs and blue stain in timber. With this new epidemic dieback, Lasiodiplodia dieback is becoming a major constraint to cocoa production and development.