Detection of Beetles in Coconut Trees Using Acoustic Emission Technique

Authors

S Arun Kumar 06M110 , B Gokul 06M112 , R Panneer Selvan 06M137

III BE Mechanical, PSG College of Technology

Abstract

The biggest threats for the coconut trees for the past 50 years are the destruction caused by the beetles like “RED PALM WEEVIL” & “RHINOCEROS BEETLE”. Normally palms that fall in the range of 1 to 13 years are more susceptible to weevil infestation. The female weevil scoops out small holes in soft tissues of the cut or damaged parts of the coconut palms and deposit eggs there. The eggs hatch in 2 to 3 days time and grubs start tunneling to the live tissues of the palm. Feeding by a number of grubs or feeding by few in the bud region results in the death of the palm. Being an internal feeder exit holes are tunneled only at the time of pupation and the presence of the pest cannot be detected at an early stage.

The symptoms manifested at the late stage of weevil infestation are the presence of holes, oozing out of viscous brown fluid and extrusion of chewed up fibers through the holes, longitudinal splitting of the leaf bases and withering of the central spindle. In severe and later stages of the infestation the sound of gnawing and the breaking of fibers could be heard in silent environment. Quite often the infestation would become evident only when the growing point of the palm is damaged and the crown is toppled.

Our system will detect the presence of the weevil in the beginning stages of tunneling the tree. The grub stage of the weevil has cutting and chewing mouth parts and when it bites the tissue, the tissue strains and the energy is liberated at certain high frequency. The waves are in the range above the audible range i.e. >20 kHz . For this we use an acoustic emission sensor to capture the sound released during the biting of tissue by the weevil. From the experiments conducted earlier we would have found the frequency of the sound produced during the biting of the weevil. Then suitable high pass and low pass filters are designed to capture for the specific frequency range. The system is controlled and monitored using LabVIEW software. A tree is monitored on a particular time and if there is any sign of weevil there will be a peak indicated in the output window from which the presence of weevil can be detected.

The advantage of using this system is that it can able to detect the presence of weevil at its initial grub stage. But the present method of detection is possible only after 35% of damage caused to the tree. At that stage controlling the pest will not be effective. Also the annual yield drops drastically even though it is detected after 35% damage.

Keywords : Weevil Infestation, Acoustic Emissions, Grub, High pass & Low Pass Filters