Companion plants as rearing and release platforms for predatory bugs in soilless tomato systems

Abstract: In this study, we assessed whether selected companion plants could serve as banker
plants for the pre-establishment and release of the predatory mirids Macrolophus pygmaeus and Dicyphus errans in soilless tomato. Preliminary laboratory and semi-field screenings identified Calendula officinalis and Geranium macrorrhizum as promising banker plants for
M. pygmaeus, and Erodium trifolium as a promising candidate for D. errans. These three
species, used alone or in mixture, were evaluated in a greenhouse trial and compared with a
conventional direct release of predators. After 50 days of pre-establishment, banker plants
significantly increased mirid abundance, particularly for M. pygmaeus, whose populations were multiplied up to 3.5-fold. Banker-plant treatments led to earlier and stronger colonisation of tomato plants than the conventional release strategy and were associated with significantly lower whitefly densities. In contrast, D. errans remained at low density throughout the trial, suggesting that the rearing protocol used was not fully suitable for this species. Among the tested options, the banker-plant mixture combined high biological performance with greater robustness. These results indicate that banker plants are a promising tool to improve preventive biological control in soilless tomato, although the system still requires refinement for D. errans and validation under commercial production conditions.