Non-invasive observations of an infestation by the peach fruit moth, Carposina sasakii Matsumura (Lepidoptera: Carposinidae) in apples using a 0.2-T compact MRI system

Using a 0.2-Tesla (T) compact magnetic resonance imaging (MRI) apparatus, we non-invasively observed an infestation of the peach fruit moth, Carposina sasakii Matsumura (Lepidoptera: Carposinidae) in harvested apple fruits. Using the 3-dimensional spin-echo method with a (470μm)³ spatial resolution, mature larvae together with accumulated excreta were detected in infested holes. This method provided stable, clear-contour images. Because measurement times ran upwards of 82min per fruit, observations of larval ecological activity in fruits were restricted to a few samples. Infested holes and excreta were also detected using the 3-dimensional gradient-echo method with an (860μm)³ spatial resolution and a 27-min measurement time. The resultant images were not as clear as those using the spin-echo method. Nevertheless, this procedure permitted larger sample sizes and thus enabled the tracking of larval movement through the examination of the expansion of infested holes. The 0.2-T compact MRI has proven to be a unique means for the ecological study of the growth and movement of the moth in apple fruits, despite the significant time required for the detection of larvae, including the measurement and rotation-processing of 3-dimensional image data, due to the relatively small sizes of larvae compared to the voxel size of the apparatus.