Characterization And Management Of Mango Sudden Decline Disease In Oman

A. Al-Adawi, M. Deadman, A. Al-Saadi, A. Al-Rawahi and Y. Al-Maqbali
College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O. Box 34, AlKhod 123, Sultanate of Oman
E-mail: Saad2000@squ.edu.om

Abstract

During early 1999, a large number of mango trees started dying in the north of Muscat area in Oman. The disease was named sudden decline in recognition of the rapid death of the affected trees, especially grafted ones, and has become more prominent over the last three years threatening mango cultivation in Oman. The bark of the affected trunks and branches exude a gum that hardens with time. Other symptoms include vascular discoloration and wilting which often begins on one side of the tree and later covers the entire tree. The etiology of mango sudden decline disease in Oman was confirmed using Koch's postulates to be caused by Diplodia theobromae and Ceratocystis fimbriata. Results from this study clearly demonstrated for the first time in Oman that bark beetles (Cryphalus scabrecollis) transmit both pathogens to healthy mango trees. Moreover, removal of the bark directly underneath the bark beetle infestation hole, revealed discoloration caused by the growth of fungal mycelium. Using scanning electron microscope, beetles were found to carry spores of C. fimbriata on their bodies. Disease incidence and severity assessments revealed that nongrafted mango trees of Omani type were more susceptible to the disease than the grafted trees. Infection and disease development for the grafted group was found to be more in the rootstock, and normally no disease symptoms were observed in the scion. Bavistin, Carbendazim and Topsin were most effective in suppressing mycelial growth of D. theobromae in vitro at 5 mg/kg.