Nano-technology for Real-Time Control of the Red Palm …
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On the one hand, the most common method of detection is the visual inspection
[15]. Visual detection and control of the RPW is difficult due to: the concealed nature
of the pest life cycle [9] and the possibility of re-infestation of the treated palms with
migrating adults from neighboring trees. Since direct visual detection of the RPW is
quite difficult, the alternative detection method is needed. In nature, different sounds
and vibrations have different origins and different functions. Bioacoustics technology
and X-rays enable the detection of the early phase of infestation, however the usage of
X-rays is expensive, but the acoustic technology [16, 17] has the potential for reducing
the expense and dangers involved in the tree inspection. The acoustic recordings from
insects in trees often reveal signals with spectral and temporal features that make
them distinctive and easily detectable [18]. Sensitive microphones and dedicated
amplifiers enable detection of the movement and feeding sounds of RPW larvae in
palm trees [19]. Due to its high reproduction rate, the RPW prefers to live with no
other insects in one trunk, which gives a good base for acoustic detection [20].
Seasonal activity of RPW catches varied significantly among months being highest
in the warmer seasons in March, April, and May in KSA, and Egypt [21, 22]. The
weevil activity was low during the monsoon between June and July. It became high
after the monsoon between October and November in Egypt while in KSA the pest
was more active during May with a second peak during November, and was low
during August and February [9]. Abe et al. [23] stated the difficulty for RPW to
overwinter in Japan, where winter temperatures is below 0 °C. When they measured
the temperature of damaged palm tissues, it was between 30 and 40 °C, even in winter.
The temperature inside a palm is between 15 and 35 °C [24]. This suggested that the
temperature plays an important role in the detection of the RPW. The RPW feeding
causes intensive plant tissue fermentation, which increases the local temperature
(30 °C and above 45 °C) inside the crown/trunk [23, 25]. The temperature rise in the
center of the crown of heavily infested palms could be detected only when viewed
from above. The natural insulation of the palm tissue prevents detection in lateral
view and also the solar radiation interferes with the thermal imaging.
On the other hand, thermal imaging is a viable alternative to point measurements.
The tunneling insects destroy the vascular system of the palm and create local conditions of water stress. This “crop water status” could be sensed through inspection of
the thermal portion of the spectrum of the reflected irradiation. Advances in remote
thermal images offer the potential to acquire spatial information on surface temperature [17] and thus facilitate the mapping of canopy temperature variability over large
areas. High-resolution thermal imaging systems have been used to evaluate the water
status of cotton [26, 27], wheat [28], vineyards [29, 30], olives [31] and peanut [32,
33]. Aerial thermal images are a promising tool to map the water status of date palm
trees [34].
Currently, there is no reliable instrument to detect infestation in the field [13]. To
the best of my knowledge, until now, rapid and comprehensive early detection and
control of RPW are not available in practice. There is a need to develop a system that
can replace traditional techniques. Therefore, the first objective of this study was to
propose an early warning system (portable and automatically) to detect the presence
of RPW along with its larva by sensing its (sound and heat) activity in offshoots. The
323
On the one hand, the most common method of detection is the visual inspection
[15]. Visual detection and control of the RPW is difficult due to: the concealed nature
of the pest life cycle [9] and the possibility of re-infestation of the treated palms with
migrating adults from neighboring trees. Since direct visual detection of the RPW is
quite difficult, the alternative detection method is needed. In nature, different sounds
and vibrations have different origins and different functions. Bioacoustics technology
and X-rays enable the detection of the early phase of infestation, however the usage of
X-rays is expensive, but the acoustic technology [16, 17] has the potential for reducing
the expense and dangers involved in the tree inspection. The acoustic recordings from
insects in trees often reveal signals with spectral and temporal features that make
them distinctive and easily detectable [18]. Sensitive microphones and dedicated
amplifiers enable detection of the movement and feeding sounds of RPW larvae in
palm trees [19]. Due to its high reproduction rate, the RPW prefers to live with no
other insects in one trunk, which gives a good base for acoustic detection [20].
Seasonal activity of RPW catches varied significantly among months being highest
in the warmer seasons in March, April, and May in KSA, and Egypt [21, 22]. The
weevil activity was low during the monsoon between June and July. It became high
after the monsoon between October and November in Egypt while in KSA the pest
was more active during May with a second peak during November, and was low
during August and February [9]. Abe et al. [23] stated the difficulty for RPW to
overwinter in Japan, where winter temperatures is below 0 °C. When they measured
the temperature of damaged palm tissues, it was between 30 and 40 °C, even in winter.
The temperature inside a palm is between 15 and 35 °C [24]. This suggested that the
temperature plays an important role in the detection of the RPW. The RPW feeding
causes intensive plant tissue fermentation, which increases the local temperature
(30 °C and above 45 °C) inside the crown/trunk [23, 25]. The temperature rise in the
center of the crown of heavily infested palms could be detected only when viewed
from above. The natural insulation of the palm tissue prevents detection in lateral
view and also the solar radiation interferes with the thermal imaging.
On the other hand, thermal imaging is a viable alternative to point measurements.
The tunneling insects destroy the vascular system of the palm and create local conditions of water stress. This “crop water status” could be sensed through inspection of
the thermal portion of the spectrum of the reflected irradiation. Advances in remote
thermal images offer the potential to acquire spatial information on surface temperature [17] and thus facilitate the mapping of canopy temperature variability over large
areas. High-resolution thermal imaging systems have been used to evaluate the water
status of cotton [26, 27], wheat [28], vineyards [29, 30], olives [31] and peanut [32,
33]. Aerial thermal images are a promising tool to map the water status of date palm
trees [34].
Currently, there is no reliable instrument to detect infestation in the field [13]. To
the best of my knowledge, until now, rapid and comprehensive early detection and
control of RPW are not available in practice. There is a need to develop a system that
can replace traditional techniques. Therefore, the first objective of this study was to
propose an early warning system (portable and automatically) to detect the presence
of RPW along with its larva by sensing its (sound and heat) activity in offshoots. The