Trichogramma are tiny wasps commonly used in augmentative biocontrol against many Lepidopteran pests. We designed a specific experimental setup to study their olfactory preferences related to egg-laying behavior. This Y-shaped olfactometer was coupled with an image-recognition model, trained with artificial intelligence, to automatically count the number of parasitized eggs. A Bayesian inference pipeline was developed to analyze the data and estimate the attraction or repulsion elicited by the tested odors. We used Trichogramma cordubensis as a model species to validate the new experimental setup, and we demonstrated that T. cordubensis females were attracted to honey and to the sexual pheromone of a potential host ( Mythimna unipuncta ), while they were repelled by vinegar or peppermint essential oil. Overall, this new experimental device will be useful for studying Trichogramma behavioral responses to odors.

•Addition of two foods was better than one for Neoseiulus cucumeris establishment.•Addition of foods plus artificial domatia promoted N. cucumeris population growth.•These supplementations enhanced the biological control efficiency of N. cucumeris.

This review aims at better understanding the employment of biocontrol plants in order to enhance the stability of populations of predatory mites in crop systems, with the ultimate goal to reduce pesticide use and to control pest mites on roses. We analyzed if plant species used in a banker plant system influenced the success in terms of quality of the harvested plant and of pest/predator numbers under greenhouse conditions, aiming at using conditions which correspond to the practice of the local producers in Southern France. The main hypothesis was that the presence of different species of biocontrol plants causes the presence of different numbers of predators and pests with a consequent different impact on crop health in a crop-pest-predator system, depending on the plants’ functional attributes. Mainly plants with domatia were efficient. They increased the number of predators, stabilized their presence throughout the weeks of experiments, and reduced numbers of spider mites. The function of domatia was analysed through additional experiments which lead to the conclusion that plants with domatia can significantly enhance biological control of the red spider mite, and that especially Viburnum tinus is suited to be employed under the climatic conditions of the Mediterranean area.

Plants added to an IPM cropping system can potentially enhance establishment of beneficial organisms and thus improve the efficiency of biological pest control in IPM greenhouses. However, despite the clear function of their presence, there is a lack of scientific knowledge about the way the additional plants function precisely. In the present study, we analyse one aspect, the importance of the presence of domatia for the presence of the phytophagous mite Tetranychus urticae and the predatory mites Neoseiulus californicus and Phytoseiulus persimilis. We employed eight potential banker plant species differing in plant architecture, the presence of pubescence, domatia or waxes, leaf texture, etc. The purpose was to identify which plant functional types enhance the reproduction of predatory mites, which banker plant species the predator and pest prefer, the characteristics of these plants and the factors responsible for this choice. We observed the distribution of all pest and predatory mite species on each plant species infested artificially, including roses as ornamental crops, after 12 weeks. The results showed that spider mites (T. urticae) and predatory mites (N. californicus, P. persimilis), plant growth and the development of both pest and predator mites were clearly affected by the presence of banker plants. No banker plant species was infested by T. urticae, contrary to bt the ornamental rose crop. Two plant species were responsible for best predator installation and rose growth, both of which had acarodomatia on their leaves which favoured the installation of predatory mites. Leaf number and height increments showed no significant differences in infested and non-infested plants of the eight plant species. In this experiment, we identified two plant species as efficient banker plants, Viburnum tinus and Vitis riparia, which hosted predators and not pests. Both are well adapted to the local Mediterranean climate and can easily be grown in open fields and greenhouses in the region. Their high tolerance to temperature extremes and drought is advantageous in the light of climatic changes to be expected. With this knowledge, practical solutions for biological pest control as an alternative to chemical control can be optimized with the aid of additional plants in the system. effects on the productivity of crop plants and enhance the effectiveness of biological pest control (Frank 2010, Huang et al. 2011). However, there is a lack of scientific knowledge of why plant species act as banker plants, and which plant morphologies and structures

In order to reduce the use of pesticides, banker plants may be added to crop systems. They can improve the presence of predatory arthropods by offering shelter or alternative food. In the present study, we analyzed basil as banker plant in a greenhouse IPM tomato crop system testing different plant combinations in monocultures vs. dicultures. We measured the influence of the presence of basil on the reduction of pest number, predator population stability, plant health and crop yield. Significantly fewer pests were present in dicultures when basil was present, but the number of predators, crop yield and leaf health was not statistically different between plant combinations. Under the given conditions, basil could not be categorized as an efficient banker plant for Macrolophus pygmaeus.

*Corresponding Author E-mail : Pia.Parolin(at)sophia.inra.fr Tel. +33 674 155172 Plants which are added to a crop system may enhance the stable presence of predators. Acarodomatia could be a valuable functional characteristic for biocontrol plants employed in Integrated Pest Management (IPM). We tested the hypotheses that presence and availability of domatia on potential banker plants increases the stability of predatory mites populations by improving their reproduction, and that the number of domatia is positively correlated with the number of mites and eggs. We chose three plant species with differing presence of domatia in a greenhouse experiment lasting five weeks, and determined the presence of pest mites Tetranychus urticae and predatory mites Neoseiulus californicus and Phytoseiulus persimilis. Adults were present on the plants independently from the presence of domatia, but eggs were laid preferentially inside domatia by both predators, but not by the pest. The predators preferred banker plants with domatia, although correlations with the number of available domatia were not relevant for the presence of both predators. In summary, the two Vitis species and Viburnum tinus are good candidates to implement biological control of T. urticae by means of a banker plant system, with a positive role of acarodomatia for the reproduction of P. persimilis and N. californicus.

Dittrichia viscose is a common plant species in the Mediterranean region which is adapted to a wide range of environmental stresses. It is an important species that can be used for phytoremediation, as bioaccumulator or bioindicator, and it has the potential for being employed in integrated pest management in the Mediterranean ecosystem due to its entomophilous character.

*Corresponding Author E-mail : Pia.Parolin@sophia.inra.fr Tel.: +33 492 38 64 36 The use of biocontrol plants to enhance IPM is an alternative to pesticide use. The presence of predatory mites, employed to control pest mites, may be enhanced by the banker plants which bear domatia and by the addition of pollen as alternative food. Our objective was to understand whether the presence of domatia and added pollen influence the predatory mites’ selection of a leaf type of a certain plant species in a positive or negative way. We hypothesized that a leaf offering shelter in form of domatia is more attractive for predatory mites if food is available on the same plant, as compared to leaves without food in form of pollen or prey. We analyzed the preferences of the predatory mite, Neoseiulus (Amblyseius) californicus (McGregor) (Arachnida: Acari: Mesostigmata: Phytoseiidae), commonly employed for biological pest control of the two-spotted spider mite. We offered two food options to N. californicus in an experiment lasting nine days on eight plant species considered as potential banker plants for N. californicus, two of them with domatia. On detached leaves in the laboratory, we compared the presence of mite on leaves with pollen and/or T. urticae as food and with/without domatia. There were clear differences of the number of mite individuals depending on the species of host plants and on food availability. The results of our study indicate that: (i) if available, the predatory mites prefer to be on the plants harboring T. urticae (roses and sweet pepper, Capsicum annuum), (ii) if only pollen is available, the two plant species which bear domatia are preferred (Vitis riparia and Viburnum tinus), and (iii) overall, the predatory mites prefer certain plant species where they can hide in domatia, even if their prey T. urticae is absent.

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.

Studies of interactions between crops, additional plants, pests and beneficial organisms already exist as well as studies of natural enemy preference, dispersal, and abundance. However, these studies focus on tri-trophic interactions from an "arthropod" point, of view. We think that in order to optimize crop protection methods we need to understand the effects that plant structures have on the various arthropods and on subsequent tri-trophic interactions. Although studies and reviews describing the role of secondary plants in Integrated Pest Management (IPM) exist, to date a general term which encompasses all plants added to a cropping system with the aim of enhancing IPM strategies has yet to be formulated. Therefore, we suggest a new term, "biocontrol plants", which we define as plants that are intentionally added to a crop system with the aim of enhancing crop productivity through pest attraction and/or pest regulation; a term that will promote the use of biocontrol services, and can ultimately lead to an increase in the sustainability of cropping systems.

Despite precautions, the spontaneous invasion of undesired arthropod pests in greenhouses seems to be unavoidable. Secondary plants can be employed in biological control to enhance the proliferation of desired natural enemies of arthropod pests. However, these additional plants may also attract pests which in turn attack the crop plants. The present study is part of a long-term experiment to test eight species of banker plants (BPs) and their efficiency for biological protection against the spider mite Tetranychus urticae, employing the predatory mite Amblyseius californicus as natural enemy. Our goal was to find the best suited local plant species to be used as BPs, which enhances the reproduction and continuous release of the predators in a greenhouse. In the present paper, we document the spontaneous invasion of arthropods on eight species of BPs in a time span of three months, in a greenhouse in Southern France. The first arthropods appeared spontaneously on some of the plants after 4-8 weeks. After three months, there were 6 additional species of arthropods (whiteflies Trialeurodes vaporariorum, rose aphids Rhodobium porosum, gall midges Feltiella acarisuga, flower thrips Frankliniella occidentalis, parasitic wasps Encarsia sp. and predatory mites Phytoseiulus persimilis). Different species of plants attracted different species of arthropods. None of the pest arthropods reproduced on the available BPs in the experimental phase and thus did not represent a problem for the ornamental crop (rose plants). This shows that the mere presence of arthropods in a greenhouse might not affect the crop, as long as there is certain diversity of plant species. Although BPs may act as involuntary multipliers for pests, our study shows that, under the given conditions, this was not the case for the chosen BPs.

Despite precautions, the spontaneous invasion of undesired arthropod pests in greenhouses seems to be unavoidable. Secondary plants can be employed in biological control to enhance the proliferation of desired natural enemies of arthropod pests. However, these additional plants may also attract pests which in turn attack the crop plants. The present study is part of a long-term experiment to test eight species of banker plants (BPs) and their efficiency for biological protection against the spider mite Tetranychus urticae, employing the predatory mite Amblyseius californicus as natural enemy. Our goal was to find the best suited local plant species to be used as BPs, which enhances the reproduction and continuous release of the predators in a greenhouse. In the present paper, we document the spontaneous invasion of arthropods on eight species of BPs in a time span of three months, in a greenhouse in Southern France. The first arthropods appeared spontaneously on some of the plants after 4-8 weeks. After three months, there were 6 additional species of arthropods (whiteflies Trialeurodes vaporariorum, rose aphids Rhodobium porosum, gall midges Feltiella acarisuga, flower thrips Frankliniella occidentalis, parasitic wasps Encarsia sp. and predatory mites Phytoseiulus persimilis). Different species of plants attracted different species of arthropods. None of the pest arthropods reproduced on the available BPs in the experimental phase and thus did not represent a problem for the ornamental crop (rose plants). This shows that the mere presence of arthropods in a greenhouse might not affect the crop, as long as there is certain diversity of plant species. Although BPs may act as involuntary multipliers for pests, our study shows that, under the given conditions, this was not the case for the chosen BPs.

We tested whether plant species used in a banker plant system influence the success of a biological control program with predatory mites. Banker plants (BP) may sustain a reproducing population of predators and provide long-term pest suppression. In an experiment lasting 12 weeks, we analyzed the responses of the predatory mite Amblyseius californicus and the pest mite Tetranychus urticae to eight species of potential BP with different morphological structures. Every BP was paired with a rose plant and infested with pest and predatory mites. The measured parameters were vitality and growth of the plants and numbers of predators, pests and their eggs. Reproduction and establishment of the pest and predatory mites differed among plant species as well as plant growth and vitality. Vitis riparia and Viburnum tinus were the most efficient BP in this combination of pest–predator species. Their presence resulted in best health of the rose crops, highest number of predatory mites and lowest number of pests. Both these BP possess domatia which may be responsible for the efficiency in hosting predatory mites. Overall, the species which fulfilled the requirements of a BP best was the local shrub V, tinus, which bore no pests and a very large number of predators and has a compact growth form suited for application in greenhouses. Although our study gives only evidence for an artificial system with a high BP:crop ratio, high numbers of introduced predators and short distances between plants, this study contributes to knowledge of BP systems and to improve the understanding of the criteria for the choice of local plant species to be used as BP for biological control in IPM.

*Corresponding author E-mail: Pia.Parolin@sophia.inra.fr Tel.: +33 492 38 64 36 Dittrichia viscosa is an entomophilous plant of the Mediterranean region known to enhance the presence of arthropods which feed on crop pests. The study tested D. viscosa in its function as potential banker plant in tomato crops using the predatory mirid bug Macrolophus pygmaeus to control whitefly pest Trialeurodes vaporariorum. In a greenhouse experiment in Southern France, the study assessed the population development of M. pygmaeus and T. vaporariorum on D. viscosa and on tomato. The question addressed was whether D. viscosa fulfils the function of banker plant while maintaining a predator population and reducing the presence of pests. The results showed that the predators did not only install on D. viscosa, but the combination of D. viscosa + tomato caused an increase of the population of the pest T. vaporariorum. On D. viscosa grown with tomato, 2246 individuals of T. vaporariorum (adults and larvae) were identified after eight weeks, in comparison to 241 on the treatment with only tomato plants and 34 with only D. viscosa. Although D. viscosa is efficient for other species combinations, it is not suitable for the protection of tomatoes against T. vaporariorum in greenhouse, and does not act as banker plant for M. pygmaeus.