Opto-Electronic determination of insect presence in fruit

摘要

Opto-electronic methods represent a potential to identify the presence of insect activities on or within agricultural commodities. Such measurements may detect actual insect presence or indirect secondary changes in the product resulting from past or present insect activities. Preliminary imaging studies have demonstrated some unique spectral characteristics of insect larvae on cherries. A detailed study on spectral characteristics of healthy and infested tart cherry tissue with and without larvae (Plum Curculio) was conducted for reflectance, transmittance and interactance modes for each of UV and visible/NIR light sources. The intensity of transmitted UV signals through the tart cherry was found to be weak; however, the spectral properties of UV light in reflectance mode has revealed some typical characteristics of larvae on healthy and infested tissue. The larvae on tissue were found to exhibit UV induced fluorescence signals in the range of 400-700nm. Multi spectral imaging of the halved tart cherry has also corroborated this particular behavior of plum curculio larvae. The gray scale subtraction between corresponding pixels in these multi-spectral images has helped to locate the larvae precisely on the tart cherry tissue background, which otherwise was inseparable. The spectral characteristics of visible/NIR energy in transmittance and reflectance mode are capable of estimating the secondary effect of infestation in tart cherry tissue. The study has shown the shifting in peaks of reflected and transmitted signals from healthy and infested tissues and coincides with the concept of browning of tissue at cell level as a process of infestation. Interactance study has been carried out to study the possibility of coupling opto-electronic devices with the existing pitting process. The shifting of peaks has been observed for the normalized intensity of healthy and infested tissues. The study has been able to establish the inherent spectral characteristic of these tissues. It was found that there existed promising futuristic possibilities to use opto-electronic sensing to estimate the degree of secondary effect of insect activities within the tissue.