Detection of live larvae in cocoons of Bathyplectes curculionis (Hymenoptera: Ichneumonidae) using visible/near-infrared multispectral imaging.

Abstract

The multispectral (MS) imaging system is a non-destructive method with potential to reduce the labour and time required for quality control in the production of beneficial arthropods such as the parasitoid Bathyplectes curculionis. In Denmark, a project is being undertaken that focuses on the possible use of B. curculionis in augmentative control of Hypera weevil pests in white clover seed production where cocoons of the parasitoid remain as a by-product of seed processing. Only a fraction of the by-product contains live parasitoid larvae and an effective method is required detect live cocoons for later augmentative control of the pest. Therefore, this study aims to identify live larval cocoons of B. curculionis using the MS imaging system. Live and dead cocoons were identified using the canonical discriminant analysis (CDA) model with an accuracy of 91% and 80% (error rate 14%) in the training set, and a predicted accuracy of 89% and 81% (error rate 15%) in the test set. Reflectance from the near-infrared region was valuable in identifying live cocoons compared with that from the visible region. The MS imaging system is a rapid method for the separation of live and dead cocoons of B. curculionis. This study shows the potential of developing an MS imaging system to facilitate sorting of live and dead cocoons and optimize augmentative control of Hypera weevil pests. © 2018 Society of Chemical Industry.