Non-destructive Observation of Peach Fruit Moth, Carposina sasakii Matsumura (Lepidoptera: Carposinidae), in Young Apple Fruits by MRI

Using a 1-Tesla dedicated magnetic resonance imager (MRI), we non-destructively observed the larvae of a peach fruit moth, Carposina sasakii Matsumura, in young apple fruits less than 30 mm in diameter. MRI detected larvae as small as 1.5 to 2.0 mm long and narrow pits in injured fruit 10 days after eclosion of adult moths. A larger larva, 10 mm long and 2 to 3 mm wide, was clearly observed, together with its excreta, in an infested fruit 15 days after eclosion. Larvae were detected in sliced images. The accumulated excreta in the fruits was visualized by maximum intensity projection (MIP) images created from 3D image data. 3D spin-echo imaging allowed the creation of high-resolution images, but it required measurement over 15 h. In contrast, 3D gradient-echo imaging required measurement for only 1 to 2 h, and could detect large larvae and their cavities in fruit. Improvement of measurement conditions will be necessary to obtain clear images of small larvae.