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EDUCATION
The study aims to find effective ways
to control and disperse the pest
A
team of researchers including Dr Ali
al Wahaibi, Ali al
Raeesi, Mohammed al Awafi,
Zakarieh al Hinai, Abdullah al
Alawi, Leila al Jahwariyah,
and Basem al Kilbani, of the
Department of Crop Sciences
in the College of Agricultural
and Marine Sciences at SQU
has conducted a study on the
dubas bug, a pest of date palms
which causes serious damage
to the tree. This study started
at the entomology laboratory
in the College of Agricultural
and Marine Sciences, and focused on three major themes:
the rearing of the dubas bug,
its natural enemies and its migration and dispersal.
Rearing of the Dubas Bug
The objective of rearing the
bug is to find a way to accelerate the bug’s growth cycle.
This process is usually ham-
pered by the long period of its
egg dormancy, which could
last for more than 3-4 months
during late spring and summer
and late fall and winter. In an
initial experiment, an attempt
has been made to reduce the
dormancy period by exposing
eggs to different temperature
regimes.
Thus, eggs were laid in
small seedlings of date palm
and were exposed to four temperatures (19.6,25,29,and 35
C). It was found that although
a temperature 29°C produced
the shortest embryonic period (ca. 30 days), the hatching of eggs staggered over a
long period of 70 days. At the
more moderate temperature
of 25°C, the first nymphs to
hatch emerged after a longer
incubation period at 29°C,
but a majority of eggs hatched
over a less staggered period
of 55 days. This resulted in
a shorter average embryonic
period at 25°C than at 29°C.
It was also observed that a
relatively large percentage of
eggs (40-90 per cent) did not
hatch at the tested temperatures even after the passage
of 5 months post egg deposition. In a second experiment
initial egg hatch started about
2 months after oviposition and
egg hatching staggered over
a long period of about five
months post egg laying.
It was noticed that egg
batches that were laid by
field-collected adult females
at room temperature(22.5°C)
and then incubated in a growth
chamber set at (ca.26.5°C),
had their initial hatching after
30 days.
Natural Enemies
Use of natural enemies is
adopted for the sake of controlling the pest. By observing
samples of egg, nymphs and
adults collected, three major
enemies were found. They are
internal egg parasitoid, egg
predator and a nymph-adult
parasitoid. Another natural
enemy observed was a red
mite clinging to the nymphs
and adults of the dubas bug,
possibly parasitising them.
Other arthropods observed on
date palm leaves in the field
and laboratory include small
preying mantis, different spider species, lady bird beetles,
larvae of lacewings, ants, and
paper wasps.
It is hoped that the Omani
farmer and the responsible authorities in the Sultanate will
take more care of these natural enemies of dubas bug by
using alternative methods of
spraying pesticides instead of
the ones which may kill useful and harmful insects. It is
advised that they should use
new pesticides that will kill
the dubas bug and spare its
natural enemies. This can also
be done by adopting a pack-
age of agricultural procedures
including pruning and cultivating date palms which are
less liable to be attacked by
this pest.
The Egg Predator
The egg predator was
found in all governorates and
regions except Al Wusta. It
could be related to or identical with the egg predator of
planthoppers and leafhoppers
on monocot crops. Within
the date palm, the predator
appeared to feed upon dubas
bug eggs laid in leaflets and
interleaflet areas.
However, more occurrences of this wasp were observed
on the midribs of leaflets than
on leaflet areas.
Moreover, a significantly
higher proportion of sites with
dubas bug were exclusively
associated with only the egg
parasitoid than with the egg
predator.
The Nymph-adult parasitoid
This species was observed
in all sampled regions and governorates except Musandam
and Assharqiyeh. ( Al Wusta
and Dhofar were not sampled)
These small wasps parasitise
on nymphs and adult insects.
The female wasp lays her
eggs inside the body of the
nymph or adult insect, and
after they are hatched, the cocoons emerge and begin feeding upon the host.
SATURday, APRIL 16, 2011
Dubas Bug’s migration and
dispersal in Jabal al Akhdar
Although date palms are
not cultivated in Jabal al
Akhdar because of the unsuitable climate, some scattered
wild palms grow in riverbeds
throughout the area. The presence of dubas bug eggs on
these trees was first detected
in 2005. In early May of 2008,
they were seen on plants other
than date palms in different locations of Al Jabal al Akhdar.
It was not clear then whether
these adults were resident on
those plants or were in transit.
Monitoring the dispersal of
dubas bugs was done by air
suction traps, and an abrupt
rise in their number was observed in mid to late April
2009.
These observations indicated that a form of mass
migration of the dubas bug
from the heavily infested date
palm gardens of low elevations around Jabal al Akhdar
to higher altitudes. This dispersal is possibly caused by
crowding and high temperatures which could be powered
by convectional hotter air currents during daytime.
Numbers on wild palms
gradually declined in May and
became very low in mid June.
First instar nymphs were observed on palms in late April
2009, while new eggs were
first observed in early May. A
second generation of nymphs
appeared in mid to late July
and continued to be observed,
though with decreasing numbers, until January 2010.
Design and Construction
of Greenhouses
D
r Yasin al Mula, of the College of Agricultural
Engineering and Marine Sciences is presently
working on modifications on the design of greenhouses
used currently in Oman. They will take place in this
second phase of the project as these modifications will be
used in constructing new greenhouses. The new design
will take into account the environmental and climatic
conditions of arid regions in Oman for the purpose of
improving the performance of the new greenhouses
to enable them to produce different crops of a better
quality, less cost, and higher yields. The performance
of these greenhouses will be assessed on the basis of
the time it takes to produce one seasonal crop. It will
take into consideration the amount and quality of the
produce, the amount of water and electricity consumed,
and the amount of the produce delivered by the current
greenhouses.
Archaeological Investigations and
Survey at Wadi al Jufr, Ja’alan
D
r Nasser Al Jahwari, of the Department of Archaeology ,
College of Arts, is currently conducting a research project
entitled: Archaeological Summary And Investigations At Wadi
Al Jufr, Jaalan area.
Dr Al Jahwari explains that this project aims at surveying
Wadi AlJufr in Wilayat Jaalan Bani Bu Hasan in Al Sharqiyah
Region, a part of Oman has not been investigated before and
remains unknown to the archaeological records of Oman.
Consequently, the project is designed to investigate the occupational history of the area, archaeological sites and features,
surface material and carry out test excavations in some selected sites. Dr Al Jahwari believes that this will necessitate full
documentation: drawing, photographing, mapping of sites and
archaeological features in the area.
The environment and geological features of the area will
also be considered. Some visits to the wadi have already been
made by the investigator and they showed that the area has
great potential that needs to be considered and documented
in great details. Among the recovered archaeological features
are Pre-Islamic and Islamic cemeteries, settlements, and towers, presenting different archaeological periods. Dr Al Jahwari
notes that one of the important archaeological aspects of the
site is the rock art where a number of rock drawings were observed along the wadi. They draw some events and activities
of the people who inhabited this area. These preliminary visits
also allowed dating of the human level activity from the late
4th millennium BC to the late Islamic times. Dr Al Jahwari
believes that the area is subject to several agents of weathering
and human activities which affect its archaeological features.
For that reason, the need to investigate the antiquity of this
area becomes explicitly urgent. Otherwise, part of Oman’s heritage remains unknown.
Study on secrets of Jatropha Dhofarica
T
he Dhofari mountainous environment is replete with several
types of trees some of which are
still used by local people for medical
purposes. The Jatropha, known in Jabali
(a local language in Dhofar) as Zebrot
grows profusely in this environment, and
is also found in tropical and non-tropical
regions around the world, but not in Europe. Mahfoutha Al Bosaidiya, a Chemistry major in the College of Science at
SQU has conducted a study on Dhofarica
under the supervision of Dr Majek Fatope of the Department of Chemistry.
The Jatropha
Mahfoutha has found out that this tree
belongs to the Euphorbiaceous family .
The name Jatropha is derived from the
Greek words ‘jastor’, which means (doctor)’ and ‘trophe’ which means (food),
which together mean an orally-taken
medicine. The Jatropha Dhofarica is
about 1.5 m. in height, has shiny green
leaves and produces a viscous milky or
red latex. Its seeds are light brown and
have a softly feel at the top.
Its shape is like an almond or a walnut. It is usually green and spherical,
and because of its nice taste it is usually
eaten by some locals. Moreover, Dhofari
mountain dwellers use its viscous latex
as a treatment for diseases like skin overspills, eye inflammations and tumours. It
is also used as an antiseptic for cough, a
pain reliever for rheumatism, its latex is
painted on camels’ breasts to ease pain
and some people use it as a deodorant.
On top of all these, it is used in circumcision.
The Study
Mahfoutha goes to say that she has
conducted a study on this tree supervised
by Dr Fatope in the period between February 2009-December 2010. The study’s
aim was to extract the effective natural
and chemical elements found in the dried
trunks of the tree and identify their chemical composition, the possibility of their
use as remedies and the degree of their
poisonousness.
By the use of chloroform, a mixture
was actually extracted from all these
elements, then, by using column chromatography, a natural and pure element
was extracted known as nonyl ferulate
ester.
Through the use of sophisticated
equipment at the Department of Chemistry, the chemical composition of this element was determined.
Conclusions
The result of this study showed that
this new element is not poisonous and
that it can be used in the treatment of
tumours and in the manufacturing of
cosmetics and sun-protection lotions. It
is hoped that more studies will be conducted on Jatropha Dhofarica and the
mixture extracted from it to identify new
elements.
Mahfoutha concludes by saying that
this plant is known world-wide as a
source of biofuel because its seeds contain 40 per cent of viscous oil that can be
used in car and plane engines as is the
case in India and the USA.