Ladybeetle (Coleoptera: Coccinellidae) Complex in Urban Green Landscapes in Spain

Parks, gardens and roadside trees and other ornamental vegetation conforming green urban landscapes are essential to maintain the urban quality of life of citizens [1]. They provide various benefits, including health, social, economic, and ecological advantages [2,3]. The vegetation of these green areas is affected by arthropod pests that cause injuries to the plants and aesthetic damages, but also disturbances to the citizens, especially by the products derived from its feeding. Recently, the most relevant tendence to avoid that pests achieve the injury levels is to prevent pest outbreaks by conservation biological control. This methodology aims to enhance ecosystem services, such as predation and parasitism, provided by already existing natural enemies in urban landscapes [4]. Achieving this goal requires precise knowledge of the natural enemy complex in a given region, including the most relevant species and the primary pest-natural enemy assemblages. In the European Mediterranean region, the most frequent groups of pests in urban green landscapes belong to the hemipteran-homopterans (aphids, psyllids, whiteflies, scales, and mealybugs). Coccinellids or ladybeetles (Coleoptera: Coccinellidae) are crucial predators of these pests, recognized for their significant role as biological control agents. This article provides an overview of the ladybeetle species complex observed in urban green landscapes in Spain, their associations with pests, and the primary habitats where they are predominantly found.

The provided information was gathered over 25 years of sampling pests in public and private parks, gardens, street trees and urban green sites of Catalonia and other regions of Spain. Ladybeetles were identified visually “in situ” or using identification keys [5-8] in the laboratory. The pest associated with the ladybeetle and the plants were also recorded.

More than 30 species have been recorded in green urban landscapes in Spain. Table 1 shows the ladybeetle species complex, their relative occurrence, association with groups of prey, and the type of vegetation habitat where they were recorded. Most of the ladybeetle species were associated with aphids in trees or shrubs, followed by those associated to scales or mealybugs. Some aphidophagous species (i.e. Oenopia conglobata L., Oenopia lyncea (Olivier) or Harmonia axyridis Pallas) were also associated with psyllids. A few species were associated with whiteflies (Clitostethus arcuatus (Rossi) and Delphastus catalinae (Horn)) and only one was associated with spider mites (Stethorus pussilus (Herbst) = S. punctillum). Four of the species recorded feed on mildews (Table 1). Species like Adalia bipunctata (L.), O. conglobata, H. axyridis, and, globally, the genus Scymnus sp., all preying on aphids and mainly living on arboreal habitats, were the most common species (Table 1). Other aphidophagous species like Adalia decempunctata (L.), Hippodamia variegata Goeze and Coccinella septempunctata L. were mainly common only in some habitats. Whereas A. decempunctata was found on trees, H. variegata was common on herbaceous plants and on shrubs (especially on oleanders, Nerium oleander) and C. septempunctata on herbaceous plants. Coccidophagous species like Cryptolaemus montrouzieri Mulsant and Chilocorus bipustulatus (L.) were recorded on trees and shrubs, preying mainly on mealybugs and scales respectively. Clitostethus arcuatus was easily found preying whiteflies on ornamental orange trees.

Table 1:Ladybeetle species identified in urban green landscapes of Spain, its relative occurrence (1: very common; 2: common; 3: infrequent; 4: very infrequent; 5: rare), main prey and vegetation habitat by order of occurrence (T: trees, S: shrubs, H: herbs).

Extensive and continuous surveillance effort done in urban green landscapes has allowed updating the previous information [9] on the occurrence and relative occurrence of the ladybeetle species complex in Spain. The ladybeetle species complex in Spanish urban landscapes is diverse and includes some of the most common species recorded in Europe [7]. There is dominance of aphidophagous species followed by coccidophagous species, which may be explained because aphids, scales and mealybugs are the most common pest in Spanish urban landscapes [10]. Some remarkable features related to several of the most common aphidophagous species can be underlined. Adalia bipunctata is naturally found in different habitats and localities but it is also the main aphidophagous species produced commercially. Its extensive and regular release in augmentative biological control programs in cities has fostered its relative abundance over other common native species [11]. In localities where O. conglobata was previously prevalent, repeated releases of A. bipunctata over the years have led to the latter becoming the dominant species. Although H. axyridis, an invasive species native to Asia, was recorded in Europe at the beginning of this century, its establishment in Spain has been recently reported [12]. Its rapid expansion in urban green landscapes has resulted in the displacement of A. bipunctata and other native ladybeetles, as observed in other European regions [11,13]. Not only species interactions, habitat requirements and prey preferences, but also plant-prey- specialization may affect the efficacy of biological control programs. Oleanders could be taken as an example. They are commonly planted in Mediterranean urban green areas and heavily infested by Aphis nerii Boyer de Fonscolombe (Hemiptera: Aphididae). It is known that this plantaphid assemblage is toxic for most of the ladybeetles. In Spain, the only species associated with A. nerii and capable of reproducing by feeding on it is H. variegata [14].

These extensive and continuous surveillance efforts conducted in urban green landscapes across Spain provides valuable knowledge into the diversity, relative occurrence, and ecological interactions of the ladybeetle species. Our findings contribute to the understanding of the relationships between ladybeetles, pests, and vegetation in urban environments. As these landscapes continue to evolve, ongoing monitoring and research efforts are essential to adapt conservation biological control strategies.

The authors would like to thank the councils of Barcelona, Vic and Lleida, the Arboretum “Pius Font i Quer” of Lleida, the IPM group of the Associació de Professionals dels Espais Verds de Catalunya and to Almudena Bigatà.

Authors declare no potential conflicts of interest.

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