Can the parasitoid Necremnus tutae (Hymenoptera: Eulophidae) improve existing biological control of the tomato leafminer Tuta aboluta (Lepidoptera: Gelechiidae)?

Necremnus tutae is native to the Mediterranean region where it has been observed in greenhouses parasitizing the invasive Tuta absoluta on tomato. The objective of the present study was to determine whether augmentative releases of N. tutae can improve existing biological control of T. absoluta based on predation by Nesidicoris tenuis. Two experiments were carried out, of which the first evaluated different N. tutae release rates (1 and 2 N. tutae m−2 week−1). The parasitoid reduced plant and fruit damage, especially at the higher rate. However, such reduction was considered insufficient given the large numbers of parasitoids needed and still unacceptable level of fruit damage. The second experiment focused on combining the most efficient rate of N. tutae of those evaluated during the first experiment, with the pre- and post-planting release of N. tenuis and supplemental additions of Ephestia kuehniella eggs. Addition of N. tutae decreased leaf damage by T. absoluta regardless the release method for N. tenuis, but the pre-plant release of N. tenuis alone was sufficient to prevent fruit damage by T. absoluta. This suggested that the addition of N. tutae may not be necessary to obtain satisfactory control of T. absoluta following pre-plant application of N. tenuis, although different options for using N. tutae in commercial crops may still be possible.