Tobacco as banker plant for <em>Macrolophus pygmaeus</em> and <em>Trialeurodes vaporariorum</em> in tomato crops

The predatory mirid bug Macrolophus pygmaeus Rambur (Heteroptera: Miridae) is commonly employed to control whiteflies Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), a common pest on tomatoes. In greenhouses of the Mediterranean, tomatoes are important crops and the need to find alternatives to pesticide use is increasing. With the aim to find biocontrol plants which are suited to maintain and multiply the populations of predators and reduce pest presence, a greenhouse experiment was performed. Different combinations were used: crop plant and pest were always present, banker plant (abbreviated as BP hereafter) and predators were present or absent. Numbers of individuals of M. pygmaeus, T. vaporariorum, and plant health were assessed. M. pygmaeus reproduced efficiently on tobacco, with the highest reproduction when only BP were present. The number of pests was significantly reduced on the plants where predators had the highest densities. However, without the presence of predators tobacco acted as an attractive plant for T. vaporariorum. Plant growth in terms of height and leaf number was not significantly different between the treatments with different species combinations. Leaf damage was higher when the BP were in a cage with tomato plants Tobacco acted as incubator for the pests when it was in a cage with tomatoes without predators present. This points to a complementarity of these two plant species to provide good reproductive conditions for the pest T. vaporariorum, an undesired synergy of plants to increase the presence of pests. Therefore, tobacco was an efficient banker plant to support the population of the predatory mirid bug M. pygmaeus, but under absence of predators it enhanced the proliferation of the pests. Its employment as BP in this combination of species is only efficient as long as predators are present.