Secondary Plants Improve the Settlement of Orius laevigatus in Greenhouses

In greenhouse systems, secondary plants are used to attract and support the multiplication of beneficial arthropods, thereby improving biological control. Three plants were selected for this study: alyssum (Lobularia maritima (L.) Desv.), yarrow (Achillea millefolium L.), and dill (Anethum graveolens L.). This study was performed in two years, 2021 and 2025, and focused on Orius laevigatus (Fieber) (Hemiptera, Anthocoridae), one of the most important predators of Thysanoptera pests in greenhouse crops. Four ornamental crops (carnation, sweet William, statice, and gerbera daisy) were included to analyse the movement and installation of the predator. Alyssum and yarrow housed O. laevigatus in both years (total mean values per sampling date of 3.0 ± 1.3 and 2.7 ± 1.0 on alyssum and 7.0 ± 2.8 and 1.8 ± 0.8 on yarrow in 2021 and 2025, respectively), increasing its population in the greenhouse. Dill was unsuitable for sustaining predator populations and attracted additional potential pests. Its short flowering period and rapid decline further limited its usefulness. Orius laevigatus adults did not show great mobility during the study and had small populations among the ornamental crops in the greenhouse. Ornamental plant statice (Limonium sinuatum (L.) Mill.) had the highest predator population. The interest of the secondary plants is discussed, highlighting their potential for biological control in greenhouses.