Comparison of transmittance and reflectance to detect insect infestation in Montmorency tart cherry

Different measurement modes, reflectance and transmittance, were compared for their ability to identify the internal insect infestation in tart cherry (c.v. Montomorency) using visible and near infrared spectroscopy. The cherries were collected in the summers of 2004, 2005, 2006 and 2007 from different orchards in Michigan. The samples included intact (Level 0) as well as infested cherries with different damage levels (Levels 1–5). The spectra were recorded for whole cherries with a spectroradiometer within a wavelength region between 550 and 950 nm. MANOVA analysis indicates that the spectral data, both of the transmittance or reflectance, basically falls into three clusters, showing that the intact cherries and the cherries with Level 1 infestation (slightly infested) are in one cluster; Samples with infestation degree from Levels 3 to 5 (seriously infested) are clearly distinguishable from the intact and slight infested samples; the cherries with Level 2 infestation degree are scattered in between the intact and serious infested samples. According to the results of the discriminant analysis, transmittance works slightly better than reflectance in terms of the total classification accuracy. Spectroscopic technology should provide the cherry industry with a valuable tool for rapidly detecting insect infestation in tart cherry.