Dicyphus bolivari Lindberg and Dicyphus errans (Wolff) (Hemiptera: Miridae) are naturally widespread in many crops with low-pesticide pressure, where they prey upon several arthropods, including the tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). However, their efficacy as biological control agents (BCAs) of this pest needs further investigations. Therefore, in this study the predatory efficacy of D. bolivari and of D. errans on T. absoluta was evaluated on tomato in laboratory and greenhouse trials. Their functional response to different numbers of T. absoluta eggs (up to 350) offered to single females or 5th-instar nymphs for 24 h was assessed in laboratory. Females and nymphs of both predators showed a high voracity and a type II functional response, with an estimated maximum predation rate per day of 189 and 194 eggs for D. bolivari females and nymphs, respectively, and 197 and 179 eggs for D. errans females and nymphs, respectively. The predators showed similar predation rates of T. absoluta eggs on plants in cage trials. However, our greenhouse trial showed that the commonly used Macrolophus pygmaeus (Rambur) (Hemiptera: Miridae), which has a lower individual predation capacity than D. bolivari and D. errans, was more effective in controlling T. absoluta than D. errans and D. bolivari because of its stronger numerical response to densities of T. absoluta and supplemental food than the other two predator species. This shows that long-term greenhouse trials, which include functional and numerical responses to pest densities, are essential to evaluate the efficacy of an omnivorous predator.
The native parasitoids Necremnus tutae Ribes & Bernardo and N. cosmopterix Ribes & Bernardo (Hymenoptera: Eulophidae) are potential biocontrol agents of the exotic tomato pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in Europe. We investigated the functional response of parasitoid females to different densities of 3rd-instar host larvae (from 3 to 40 hosts offered), as well as some life history traits (longevity, lifetime fecundity, parasitism and host-feeding rate) of N. tutae and N. cosmopterix. In functional response experiments, the rate of attack of both parasitoids was positively correlated with host density, N. tutae and N. cosmopterix showing type III and type II functional response, respectively; the latter species exhibited a higher maximum estimated host-killing rate than the former. Both parasitoids showed high fecundity (> 50 eggs) during their lifetime. The potential application of N. tutae and N. cosmopterix in conservation biological control of T. absoluta is discussed.
The Palaearctic predator Dicyphus errans (Hemiptera: Miridae) lives omnivorously on various host plants, preying on a wide range of small arthropods, including some new invasive alien species. These characteristics make it a promising biological control agent (BCA) in organic greenhouses. The capacity of a BCA to find, kill and consume prey plays a fundamental role in trophic interactions and population dynamics in a predator-prey system. The functional response of a predator, which describes how the individual rate of prey consumption changes in response to prey density, is a key component to assess its effectiveness in pest control and the stability of its own populations. Therefore, the functional response of D. errans on different prey was studied to improve our knowledge on the potential of this mirid, which is naturally widespread in European organic greenhouses. Laboratory experiments were carried out on three exotic pests: the poinsettia thrips Echinothrips americanus (Thysanoptera: Thripidae), the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), and the tomato borer Tuta absoluta (Lepidoptera: Gelechiidae), to build functional response curves. Prey was offered at different densities to single females of D. errans for 24 h. The predation behaviour of D. errans on all the prey species was defined by Type II functional response curves. The female could daily prey about 62 adults of E. americanus, 114 pupae of T. vaporariorum, and 236 eggs of T. absoluta. The high voracity of this generalist predator on different prey confirmed its suitability as a BCA. For effective and stable pest control strategies, a prior to pest establishment of D. errans in organic greenhouses may prevent pest escaping in case of high infestation rates, even if the type II functional response reaches saturation at very high prey densities.
Dicyphus errans (Wolff) has been shown to be a suitable biocontrol agent for Tuta absoluta (Meyrick). This generalist predator shares various host plants with the exotic pest, and these interactions could be exploited to enhance pest control. Therefore, host preference, survival rate and development times of the predator and prey were investigated on crop and non-crop plant species. Among the tested plants, the favourite hosts were Solanum species for T. absoluta, and herb Robert, European black nightshade, courgette and tomato for D. errans. Tuta absoluta accepted the same plant species as hosts for oviposition, but it never developed on herb Robert and courgette in all the experiments. Based on our results, we would suggest the use of courgette and herb Robert in consociation with tomato and as a companion plant, respectively, which may keep pest densities below the economic threshold. Moreover, the omnivorous and widespread D. errans could be a key predator of this exotic pest, allowing a high encounter probability on several cultivated and non-cultivated plant species.
All of the published studies but one about the diet of the Eurasian scops owl Otus scops, a nocturnal raptor of conservation concern, were carried out during the breeding period, just before or immediately after the chicks fledged. The species is a trans-Saharian migrant with few resident populations in Europe. Orthoptera make up the staple of its diet in summer. In this study, we investigated the diet of scops owls on the island of Pianosa after the breeding period through the analysis of pellets. A total of 327 fragments belonging to at least 14 taxa were identified from 56 pellets collected after the breeding period, between late August and March. By frequency, invertebrates constituted 80.00% of the diet, with Coleoptera being the most represented order (62.35% of the total diet) and Orthoptera poorly represented (8.24%). Vertebrates included two bird species, three small mammals and the Moorish gecko. Although the meal-to-pellet interval for scops owls is unknown, we suggest that the bank vole, which is not recorded on any Italian island, and possibly the wild mice, may have been preyed upon in nearby areas, before a migratory movement towards a warm area (e.g. Pianosa) occurred.