|
Mango Tree Mortality
By Dr. Rab Dino Khuhro, Dr. Shafi
Muhammad Nizamani,
M. Mithal Jiskani and Qamaruddin Abbasi
Causes, Symptoms and Control strategies through IPM
Mango, Mangifera indica L. is
one of the most important fruit which is exported to many
countries such as Dubai, Saudi Arabia, UK, Germany, France,
Holland, Switzerland, Italy, Singapore and Malaysia. It is
known as "King of Fruits" and is consumed both by poor and
rich people. It is a rich source of vitamin A, B and C. Ripe
pulp of mango provides 74 Kcal of energy per 100 grams of
edible portion.
 According
to general composition it contains moisture (79.2-82%),
total soluble solids (12.9-20.8%), total sugars (10-17.3%),
non-reducing sugars (7.27-12.35%), ash (0.49-0.58%) and
crude protein (0.38-0.62%) on fresh weight basis. The
compounds mangshopanal and mangoleanone, isolated from the
stem bark of Chaunsa mango cultivar are used to treat
haemoptysis, nasal catarrh, hemorrhages, malaena, diarrhoea,
diphtheria, rheumatism and lumbrici (Sharma and Ali, 1994).
Apart from this, unique mango recipes such as ice cream,
milk shake, squashes etc. are favorite desserts. Mango
juice, jelly, marmalade, pickles are also commonly consumed.
There are numerous varieties of the mango, each differing in
fruit characters, viz. taste, flavor, color, tinge, shape
and size, which determine the quality of the fruit and its
market value at home and overseas (Talpur
et al., 2002).
The mango is known to suffer from a number of insect pests
and diseases. However, mango hopper, thrips, scale insects,
fruit flies and stem borers are considered serious insect
pests, but the present situation of mango orchards, with
special reference to the province of Sindh (2-20%) of mango
trees are dying suddenly, depending upon the management of
gardens.
Although the growers reported that the negligible mortality
of mango trees was observed from 5 to 7 years, but no one
paid attention to it and the mango trees were replaced by
new seedlings. Main reason of sudden mango mortality is
minute beetle known as Asian ambrosia beetle, Xylosandrus
crassiusculus Mot. (Coleoptera:
Scolytidae), which makes the tiny holes in root,
stem, branches and blocks the flow of nutrients in phloem
and xylem vascular bundles. Concurrently, the gum with
different colors depending upon period of exudation, mainly
milky at initial time, which turns light yellow to reddish
brown in color which oozes out from the trunk and branches
ultimately plant mortality, takes place within few days.
The beetle causes mortality of mangoes one by one in line.
Only females have wings and disperse with small movements.
The Asian ambrosia beetle is reported attacking on a wide
range of 124 hosts (Schedl, 1962;
Atkinson et al., 2000; Bambara et al., 2003), and
inoculates the galleries with different species of fungi.
Pathan et al. (2004) isolated F. equiseti as the most
frequent fungus from dried branches, stems and roots of
Langra (35.0-62.25%), Chaunsa (30.0-55.30) , Sindhri
(15.20-35.20) and Siroli (12.25-20.25%) mango varieties with
maximum disease severity index (DSI) in Langra (56.20%).
CAUSES
Asian ambrosia beetle is vector insect pest and different
fungi are killers of mango trees. This relationship of
insect and disease complex is like Anopheles female mosquito
(vector) and malarial disease.
The spores of fungi complex remain inside bark and can't
migrate from infected mango tree to healthy trees whereas,
bark beetle migrates from infected trees and inoculates the
spores in other healthy trees standing near by where the
pathogens multiply and kill the mango trees. In this way the
disease spreads. Different fungi like Fusarium,
Botryodiplodia and Colletotrichum spp. etc. are isolated
from different infected mango trees.
Basically, this is a management problem. The owners of mango
gardens give their gardens on contract and forget about care
of their gardens whereas, contractors don't apply proper
fertilizer, cultural and plant protection practices as per
requirement of the gardens. In this way, the problem of
mortality in mango is multiplying. If this is the scenario
we shall end up with mango cultivation and loose export
exchange in next few years. The mango growers are strongly
advised to expend at least 10% of their income on management
operations for the sustainability of mango fruit in their
own interest and country at large; therefore, garden owners
must not depend on contractors.
SYMPTOMS
Asian ambrosia beetle and the fungi have been collected from
various samples of dead or partially dead mango trees during
different visits round the year. The beetle has stout dark
reddish-brown body and is reported as pest on broad host
range including woody ornamentals, fruit and nut trees (Atkinson
et al., 1988; Kovach, 1986). It spreads from infested
and dead mango trees, wood logs/pieces and by its own short
movements. These beetles are so tiny that initially attacked
trees don't show symptoms. In case of severe infestation,
the small pin head sized holes appear with the inside and
outside movement of beetle on bark. The beetles excavate
galleries in the branches, trunks, roots and twigs. The
beetles introduce fungi complex in the mango tree and lay
their eggs in clusters. In some mango trees no holes in bark
appear but black spots on the basal parts of trunks are
present. After cutting those barks, the light yellow paste
with bad odor watery secretion flows. The beetles are also
present in infested black basal part of the trunk. The gum
like secretion/drops commonly known as gummosis oozes out
from holes of trunks/branches of mango trees infested with
beetle. The "C" shaped legless white grubs of beetle are
found feeding on inner darkened portion of barks. From the
infested trunk of the mango tree, the frass of the beetle is
pushed out of galleries in a typical tooth-pick fashion.
IPM STRATEGIES against A. A. beetle, other pests and
diseases
• Regular monitoring of A. Ambrosia
beetle, other pests and diseases of mango at weekly interval
is compulsory.
• Removal and burning of diseased/dead mango trees including
roots is most important.
• Prune infested/diseased branches along with 4-5 inches of
healthy portion with saw and paste the cut points as advised
by the experts in July-August or when needed.
• Plowing/interculturing and other sanitation practices of
garden in July-August followed by pruning are suggested.
• Soil testing is compulsory for application of chemical
fertilizers. Zinc sulphate and other macro and micro
nutrients may be incorporated on the basis of soil testing
in July-August.
• The spray of suitable insecticide in combination with
compatible fungicide (washing of trunk and branches) is
advised against A. A . Beetle, other pests & diseases,
whenever necessary during monitoring.
• Spray of suitable insecticide and fungicide against mango
hoppers and powdery mildew is proposed before flowering in
1st fortnight of December.
• At the time of inflorescence, if there is attack of mango
hoppers and powdery mildew get advice from IPM experts for
application of suitable pesticides without delay.
• Malformed mango inflorescences (flowers) must be cut
off/removed and burned out or deep buried immediately before
application of pesticides against mango hoppers and powdery
mildew.
• If thrips and powdery mildew occur over newly developed
fruits/flush then consult with IPM experts for remedy.
• Installation of pheromone traps at 8 per acre at height 6'
above ground under the shade of trees is suggested in
May-June with replacement of trap lure (cotton wick) after
every 15-20 days.
Attention
A. It must be kept in mind that
the pesticides (insecticides
and fungicides) are equally
hazardous to all livings, hence be applied only on the
recommendations of experts.
B. No doubt the mango bark
beetle problem under discussion is new in our region but
same has been reported in other mango growing countries.
Following few attention points are once again recommended
for benefit of mango growers.
• Beetles will continue to develop and
emerge from uprooted and dead trees, so removed plants
should be burned. These beetles are very destructive and
will quickly destroy nursery and landscape stock in large
numbers. Ambrosia beetles represent a real threat to nursery
and landscape trees.
• Infested trees should be destroyed
before the beetles emerge.
• Personnel from all segments of the
mango industry should be alert to this difficult pest
problem and communicate with each other the species, host
plants, timing and degree of infestations. The population
dynamics of these ambrosia beetles remains unpredictable and
everyone with trees is probably at risk.
• Sheesham (Talhi), Gular, Gold Mohar,
Teak, Sufedo (Eucalyptus) and Sareenh (Albizia) are recorded
as alternate host plants of Asian Ambrosia beetle in Sindh.
• Growers are also advised to monitor
their gardens regularly and remain in contact with experts,
so that proper chemical control could be applied in the
interest of mango grower as well as for nation and country.
• Frequently use of pesticides without
need must be avoided.
• Different tree species serve as
alternate hosts of insect pests including Asian ambrosia
beetle and pathogens causing damage to mango orchards.
Therefore, all infested alternate hosts must be removed from
orchards and surroundings on priority basis.
M. Mithal Jiskani is a
permanent contributor to Pakissan.com.
|
Other Overviews
|
DISCUSS
issue
problems
at
Pakissan Forum
Connect with
the
Pak Agri Community
|
Register
Today at
Pak
APIN
(Pakissan
Agri Experts and Institutes Network)
& become
part of the
Agri
Community
of
Pakistan
|
|
|
