No abstract

Ecological communities used in biological pest control are usually represented as three-trophic level food chains with top-down control. However, at least two factors complicate this simple way of characterizing agricultural communities. First, agro-ecosystems are composed of several interacting species forming complicated food webs. Second, the structure of agricultural communities may vary in time. Efficient pest management approaches need to integrate these two factors to generate better predictions for pest control. In this work, we identified the food web components of an avocado agro-ecosystem, and unravelled patterns of co-occurrence and interactions between these components through field and laboratory experiments. This allowed us to predict community changes that would improve the performance of the naturally occurring predators and to test these predictions in field population experiments. Field surveys revealed that the food-web structure and species composition of the avocado community changed in time. In spring, the community was characterized by a linear food chain of Euseius stipulatus, an omnivorous mite, feeding on pollen. In the summer, E. stipulatus and a predatory mite, Neoseiulus californicus, shared a herbivorous mite prey. Laboratory experiments confirmed these trophic interactions and revealed that N. californicus can feed inside the prey nests, whereas E. stipulatus cannot, which may further reduce competition among predators. Finally, we artificially increased the coexistence of the two communities via addition of the non-herbivore food source (pollen) for the omnivore. This led to an increase in predator numbers and reduced populations of the herbivore. Therefore, the presence of pollen is expected to improve pest control in this system.

Aim of study: The globally invasive gall wasp, Dryocosmus kuriphilus Yasumatsu, 1951 (Cynipidae: Cynipini), reached Spain seven years ago and is already regarded as an important pest of chestnuts (Castanea spp.) in this country as well as worldwide. In this paper, we present comprehensive data on the establishment in Spain of Torymus sinensis Kamijo, 1982 (Chalcidoidea: Torymidae), an effective non-native natural enemy of this pest, as a result of both natural dispersal and settlement after controlled releases since 2015.Area of study: Sites of the Spanish autonomous communities of Galicia, Asturias, Basque Country, Catalonia, Andalusia and Madrid where D. kuriphilus is present.Material and methods: To study the natural dispersal of T. sinensis from France, we selected two sampling sites in Catalonia, six in the Basque Country and two in Navarra known for their heavy Asian chestnut gall wasp (ACGW) infestation; to study T. sinensis establishment after authorized controlled releases by the concerned authorities, the field samplings were done mainly in Galicia (35 sites) and Andalusia (8 sites). Additionally an experimental release study was made in Madrid.Main Results: Our results showed that T. sinensis has spread throughout Spain by natural dispersal across the French border and now occurs in Catalonia (two sites), the Basque Country (three sites) and Navarra (one site) but not in the neighbouring region of Cantabria. The percentage of parasitism by T. sinensis on D. kuriphilus is higher in the Basque Country sites, which are close to the French border, thus indicating that its establishment in these localities is not recent. After controlled releases, T. sinensis has been successfully established in five release sites in Andalusia (Valle del Genal and Sierra Blanca, Málaga Province) and one release site in Madrid. However, in the region of Galicia (NW Spain), where the number of authorized releases has been higher, the establishment of T. sinensis still appears to be very low.Research highlights: Established populations of T. sinensis may exert a positive buffer against D. kuriphilus-driven chestnut infestation in Spain, similar to what is observed in other invaded European countries.Additional Keywords: Controlled releases, Torymidae, invasive species, Cynipidae, natural spread, biological control.Abbreviations used: Asian chestnut gall wasp (ACGW); Torymus sinensis parasitism rate (TsPR); mean of ACGW larval chambers per gall (MACGW).

Mite diversity of selected citrus orchards in Andalusia (southern Spain) was studied during 2002-2007. The following species were found: Eutetranychus orientalis, Tetranychus urticae, Panonychus citri (Tetranychidae), Tydeus californicus, Lorryia formosa (Tydeidae), Pronematus ubiquitus (Iolinidae), Euseius stipulatus, Typhlodromus phialatus, Neoseiulus californicus, Euseius scutalis, Phytoseiulus persimilis, Paraseiulus talbii and Neoseiulus cucumeris (Phytoseiidae). Eutetranychus orientalis was the dominant tetranychid species in orange and lemon trees, whereas T. urticae was slightly more abundant in mandarines. The most abundant tydeid in clementine and orange was Tydeus californicus, in lemon it was L. formosa. The iolinid P. ubiquitus was found in very low numbers. With respect to phytoseiids, E. stipulatus was dominant in the three citrus species. Eutetranychus orientalis had a unimodal phenology, peaking only in autumn, whereas the other two tetranychids had two maxima. Tydeus californicus showed one or two peaks depending upon the citrus species, and E. stipulatus also had two peaks, one in spring and one in autumn. The mites displayed a non-random distribution in the tree. Eutetranychus orientalis preferred the outer and upper leaves. On the contrary, tydeids (mainly T. californicus) and phytoseiids (mainly E. stipulatus) preferred inner and lower leaves. These preferences had not been sufficiently described previously, and they are important for sampling plans.