Establishment and Expansion of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in Urban Green Areas in the Iberian Peninsula: From 2015 to 2021.

In the Western Palearctic region, Harmonia axyridis (Coleoptera: Coccinellidae) is mainly established in urban areas. In this study, we update its occurrence in urban areas of the Iberian Peninsula and determine its expansion after 2014. Changes in the ladybird species assemblage are also evaluated. We compile information about the records of H. axyridis in Spain from 2015 to 2021. In addition, we sample different locations to determine the relative abundances of the species composing the aphidophagous ladybird complex. The expansion of H. axyridis mainly occurred in Catalonia (Iberian Peninsula), where it is possible to identify two clear areas: one that has already been invaded and another that has not yet been invaded. Harmonia axyridis became the dominant species in the invaded area two years after it was first identified. This dominance is clearly shown on Liriodendron tulipifera and Tilia platyphyllos, where it accounted for more than 75% of the total collected individuals in the last year of the study. In the not-yet invaded area, Adalia bipunctata overcame Oenopia conglobata and became the prevalent species from 2020 onwards, likely due to its regular releases for aphid biocontrol. This study reveals that changes in ladybird species assemblages may not only be caused by invasive species, but also by biological control practices.

Prey Acceptability and Preference of Oenopia conglobata (Coleoptera: Coccinellidae), a Candidate for Biological Control in Urban Green Areas.

Oenopia conglobata is one of the most common ladybird species in urban green areas of the Mediterranean region. We have obtained data about its prey acceptability and prey preferences. In a laboratory experiment, we investigated the acceptability of seven aphid and one psyllid species as prey for this coccinellid: the aphids Chaitophorus populeti, Aphis gossypii, Aphis craccivoraMonelliopsis caryae, Eucallipterus tiliae, Aphis nerii (on white poplar, pomegranate, false acacia, black walnut, lime, and oleander, respectively), and the psyllid Acizziajamatonica on Persian silk tree. These species are abundant in urban green areas in the Mediterranean region. In addition, we tested the acceptability of Rhopalosiphum padi on barley, an aphid species easily reared in the laboratory. We also tested preferences of the predator in cafeteria experiments with three aphid species and one aphid and the psyllid. Adults and larvae of the coccinellid accepted all of the preys offered, except A. nerii, with a clear preference for M. caryae. The predator also showed preference for M. caryae when it was offered in a cafeteria experiment with other aphid species or with the psyllid. The aphid R. padi obtained a good acceptability and could be used for rearing O. conglobata in the laboratory.

Responsiveness of arthropod herbivores and their natural enemies to modified weed management in corn.

Alteration of weed flora as consequence of the deployment of genetically modified herbicide-tolerant crops may affect higher trophic levels in agrosystems. A 4-yr study is being conducted in Spain to investigate interrelations between weeds and associated arthropods in corn fields. In a first step, the work aimed to detect the most responsive arthropods to weed management changes. To identify the most responsive arthropods, arthropod composition and abundance in herbicide-tolerant corn plots treated twice with glyphosate and untreated plots were compared for 2 yr. Plots were sampled seven times during the season by visual inspection and pitfall and yellow sticky traps to estimate abundance and activity of the main arthropod herbivores, predators, and parasitoids. As intended, the abundance and composition of weed flora was strongly altered by the differential herbicide treatments. Several groups of arthropods responded to the weed changes but in variable directions. Whereas leafhoppers and aphids were more abundant on herbicide-treated plots, the contrary was found for phytophagous thrips. Among predators, Orius sp., spiders, and trombidids were more abundant on treated plots, whereas nabids and carabids were more abundant in untreated plots; the same case was found for carabids and spiders caught in pitfall traps. Among parasitoids, ichneumonids were more abundant in untreated plots and mymarids in treated plots. These results cannot be interpreted in terms of nontarget effects of postemergence treatments with broad-spectrum herbicides; for this, a comparison with conventional weed management practices should be done and this is the current step in the study.

Six years after the commercial introduction of Bt maize in Spain: field evaluation, impact and future prospects.

We carried out a 6-year-field evaluation to assess potential hazards of growing Compa, a transgenic Bt maize variety based on the transformation event CG 00256-176. Two categories of hazards were investigated: the potential of the target corn borer Sesamia nonagrioides to evolve resistance to Bt maize and effects on non-target organisms. In order to address the first hazard, dispersal capacity of the corn borer was measured and our results indicated that larvae move to plants other than those onto which the female oviposited - even to plants in adjacent rows - in remarkable numbers and they do so mostly at a mature age, suggesting that mixing Bt and non-Bt seeds in the same field would not be a very useful deployment strategy to delay/prevent resistance. In addition, adults move among fields to mate and males may do so for up to 400 m. Three different aspects of potential non-target effects were investigated: sub-lethal effects on the target S. nonagrioides, effects on non-target maize pests, and effects on maize-dwelling predators. Larvae collected in Bt fields at later growth stages, in which event 176 Bt maize expresses Bt toxin at sub-lethal concentrations, had longer diapause and post-diapause development than larvae collected in non-Bt fields, a feature that might lead to a certain isolation between populations in both type of fields and accelerate Bt resistance evolution. Transgenic maize did not have a negative impact on non-target pests in the field; more aphids and leafhoppers but similar numbers of cutworms and wireworms were counted in Bt versus non-Bt fields; in any case differences in damage or yield were recorded. We observed no difference in the numbers of the most relevant predators in fields containing transgenic or no transgenic maize.