Published Date: 2002-12-13 23:50:00
Subject: PRO/PL> Mango sudden decline - Oman (Al Batinah Region)
Archive Number: 20021213.6053
MANGO SUDDEN DECLINE - OMAN (AL BATINAH REGION)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: 12 Dec 2002
From: ProMED-mail <email@example.com>
Source: Brit Soc Plant Pathol, NEW DISEASE REPORTS [edited]
_Diplodia theobromae_ associated with sudden decline of mango in the
Sultanate of Oman
A.O. Al Adawi <firstname.lastname@example.org>, M.L. Deadman, A.K. Al Rawahi,
A.J. Khan, Y.M. Al Maqbali, Department of Crop Sciences, College of
Agricultural and Marine Sciences, Sultan Qaboos University, P O Box
34, Al Khod 123, Sultanate of Oman. Accepted for publication 3 Dec
Mango (_Mangifera indica_) is an important crop in the Sultanate of
Oman, producing 12 000 tons from 1500 ha annually. Grafted and
non-grafted trees are cultivated, the former using exotic scions on
local rootstocks. Non-grafted trees are selections from trees with
good fruit qualities.
Since 1999 a new disease has appeared, affecting up to 60 percent of
trees in parts of the coastal Al Batinah region. Infected trees show
gummosis from the trunk, wilting, and eventual browning of leaves on
a single branch.
As infection progresses death occurs, perhaps 6 months from first
appearance of symptoms. The wood is stained dark brown, spreading
from a point of infection. Damage caused by a bark beetle (_Cryphalus
scabrecollis_), is frequently associated with the disease.
Pycnidia are observed in lesions on infected bark and the pathogen,
_Diplodia theobromae_ [Dt] (IMI Reference W6341), has been isolated
from affected trees. When inoculated to healthy seedlings, Dt
fulfills Koch's postulates. Dt has been isolated from bark beetles,
suggesting the insect may act as a vector for dispersal.
Non-grafted (Omani) trees show higher levels of disease severity than
exotic scions (65 percent and 14 percent, respectively). Insect
damage is significantly less on exotic scions than on local,
non-grafted trees. Insect log traps protected with polyester fleece
to exclude the beetle showed no symptoms, while logs left unprotected
were quickly infested with beetles and showed wood-staining.
Dt-induced citrus die back has been reported from Oman (Waller &
Bridge, 1978). Research to evaluate varietal resistance to the
disease and vector, potential management techniques, and relationship
with _Ceratocystis fimbriata_, a pathogen that has occasionally been
isolated from trees showing mango decline symptoms, continues.
Waller JM Bridge J, 1978. Plant diseases and nematodes in the
Sultanate of Oman. PANS 24, 313-326.
[I suspect that the main point of this piece is the identity of a
pathogen that causes sudden mango decline (as opposed to mango
decline). It would be instructive if any of our readers know if Dt
has been implicated in mango decline. Please let me know. - Mod.DH]