Exotic predators are not better biocontrol agents: the harlequin ladybird is not the most voracious in Mexico

The use of exotic species for pest biocontrol has been a common pathway for introduction and dispersal of invasive species that may have undesired outcomes. Biocontrol agents are believed to be a less damaging alternative than pesticides, but some species may also prey on or parasitize native species or outcompete them for resources. The harlequin ladybird (Harmonia axyridis) is a well-known biocontrol agent originally from Asia that has established invasive populations in 59 countries around the globe. Harlequin ladybirds are generalist predators that in addition to pests prey on an array of different species including other coccinelids’ eggs and larvae. In Mexico, native ladybirds that share ecological requirements with harlequin ladybirds are at risk of being outcompeted and predated upon. The aim of our study was to compare the foraging efficiency of harlequin ladybirds against three species of native coccinelids when preying on aphids. We investigated the foraging behaviour of ladybirds alone and in pairs with a conspecific, a native heterospecific or an exotic heterospecific. We found that the native Cycloneda sanguinea was the species that consumed the most aphids, while Hippodamia convergens was the fastest to find and consume each aphid. Harlequin ladybirds and H. convergens consumed the same number of aphids while P. vittigera consumed less. Conspecific competition was stronger than heterospecific competition. We discuss the suitability of using the exotic invasive harlequin ladybird for aphid biocontrol in comparison with native coccinelids.

PREVALENCE AND DISTRIBUTION OF DIFFERENT NATURAL ENEMIES IN THE HARLEQUIN LADYBIRD HARMONIA AXYRIDIS (COLEOPTERA COCCINELLIDAE)

The harlequin ladybird Harmonia axyridis (Coleoptera: Coccinellidae) is one of the most common invasive alien species in the world, which has a global impact on biodiversity and agriculture, and causes economic loss and harm to humans. This insect can be infected by different natural enemies, but their interactions remain understudied. In the present study, 581 adult Ha. axyridis specimens were collected from 21 localities in Hungary with the help of citizen scientists and examined for natural enemies. The parasitic nematode Parasitylenchus bifurcatus (Nematoda: Allantonematidae) is reported in Hungary on the harlequin ladybird for the first time. The ladybirds were also infected by the ectoparasitic fungus Hesperomyces virescens (Ascomycota: Laboulbeniales) and parasitoid Dinocampus coccinellae (Hymenoptera: Braconidae). The nematode parasite was present in all localities where Hesperomyces-infected ladybirds appeared. The prevalence of recorded natural enemies varied by locality: for P. bifurcatus it ranged from 1% to 8%; for He. virescens from 2% to 36%; and for the parasitoid it was 4%. Besides, a statistically significant positive correlation was shown between the nematode and the fungus co-infection using Spearman’s correlation. A study on the multiparasitism of harlequin ladybirds was not yet performed in Hungary. The study area is located between two distant areas in Europe where co-infections had already been observed, indicating that this is probably not a sporadic phenomenon, but that parasitism of the harlequin ladybird by multiple natural enemies might be prevalent throughout the area.

Does the non-native Harlequin ladybird disrupt the feeding behaviour of the native two-spot ladybird?

Since its arrival in 2004, the non-native Harlequin ladybird Harmonia axyridis (Coleoptera: Coccinellidae) has rapidly spread throughout Britain, and it is now the most common coccinellid in England. There have since been concerns about the detrimental effects it may have on native coccinellids because there is a strong correlation between the arrival of H. axyridis and the decline in native species, including the two-spot ladybird, Adalia bipunctata. However, there have been few studies of the behavioural interactions between these two species, which occupy a high-niche overlap. This study investigated if the presence of H. axyridis impacts the feeding behaviour of A. bipunctata through direct competition for aphid prey. Foraging and interactive behaviour of A. bipunctata and H. axyridis were investigated within microcosms. Adalia bipuncata exhibited a similar consumption rate and time in the presence of H. axridis, yet H. axyridis consumed 3.5 times more prey items and were seven times faster compared to A. bipuncata. Observations showed that H. axyridis does not directly disrupt the feeding behaviour of A. bipunctata, but rather indirectly excludes the native species through being a superior competitor for prey items. Results indicate that the decline in native coccinellid species may be a consequence of H. axyridis competitive advantage, but that the concept of coexistence should not be dismissed.

Transgenerational Effects of a Neonicotinoid and a Novel Sulfoximine Insecticide on the Harlequin Ladybird

The harlequin ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), is a generalist predator and an effective biocontrol agent of various insect pests that has been exploited for the control of aphid pests in the greenhouse and field. However, insecticides are widely used to control aphid pests worldwide and the potential non-target effects of sulfoxaflor and imidacloprid for controlling aphid pests towards this biocontrol agent are little known. Although both sulfoxaflor and imidacloprid act on nicotinic acetylcholine receptors of insects, sulfoxaflor has a novel chemical structure compared with neonicotinoids. We assessed the lethal, sublethal and transgenerational effects of sulfoxaflor and imidacloprid on H. axyridis simultaneously exposed via ingestion of contaminated prey and via residual contact on the host plant at LC20 and LC50 doses estimated for the cotton aphid. Imidacloprid significantly reduced the survival of H. axyridis adults compared to sulfoxaflor at the same lethal concentration against cotton aphid. Both concentrations of imidacloprid and sulfoxaflor reduced the proportion of ovipositing females, and both concentrations of imidacloprid and sulfoxaflor, except LC20 dose of sulfoxaflor, reduced the fecundity and fertility of the parental generation. In the progeny of imidacloprid- and sulfoxaflor-exposed parents, both tested LC50 concentrations significantly decreased the juvenile survival rate, and both concentrations of imidacloprid and sulfoxaflor, except LC20 dose of sulfoxaflor, prolonged the development time. Our findings provide evidence of the negative influence of imidacloprid and sulfoxaflor at low lethal concentrations on the harlequin ladybird and on the progeny of exposed individuals, i.e., transgenerational effects. Hence, these findings stress the importance of optimizing the applications of imidacloprid and sulfoxaflor for the control of aphid pests, aiming at preserving the biocontrol services provided by H. axyridis throughout the integrated pest management approach.

A Field Guide to Harlequins and Other Common Ladybirds of Britain and Ireland

The invasive Harlequin ladybird is an eye-catching and beautiful species, but it can be very difficult to identify, with huge variation in colouration and pattern. This comprehensive photographic field guide is the first complete guide to identifying Harlequin ladybirds found in Britain and Ireland. It also covers all the other 25 conspicuous ladybird species that occur. - Detailed, informative and beautifully illustrated with more than 350 remarkable colour photographs including ladybird developmental time sequences and numerous images of each ladybird species - Ground-breaking quick key for Harlequin identification - Includes a photographic guide to the larvae of all 26 species – the first of its kind - Easy to follow comprehensive descriptions and explanations of ladybird lifecycles and habits This clear, user-friendly field guide is ideal for anyone interested in learning how to identify a Harlequin ladybird, from beginners to more experienced entomologists, students and professionals. This book is ideal for learning to recognise and understand this charismatic and significant beetle.

Antennal transcriptome analysis and identification of candidate chemosensory genes of the harlequin ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

In predatory ladybirds (Coleoptera: Coccinellidae), antennae are important for chemosensory reception used during food and mate location, and for finding a suitable oviposition habitat. Based on NextSeq 550 Illumina sequencing, we assembled the antennal transcriptome of mated Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) males and females and described the first chemosensory gene repertoire expressed in this species. We annotated candidate chemosensory sequences encoding 26 odorant receptors (including the coreceptor, Orco), 17 gustatory receptors, 27 ionotropic receptors, 31 odorant-binding proteins, 12 chemosensory proteins and 4 sensory neuron membrane proteins. Maximum-likelihood phylogenetic analyses allowed to assign candidate H. axyridis chemosensory genes to previously described groups in each of these families. Differential expression analysis between males and females revealed low variability between sexes, possibly reflecting the known absence of relevant sexual dimorphism in the structure of the antennae and in the distribution and abundance of the sensilla. However, we revealed significant differences in expression of three chemosensory genes, namely 2 male-biased odorant-binding proteins and 1 male-biased odorant receptor, suggesting their possible involvement in pheromone detection. Our data pave the way for improving the understanding of the molecular basis of chemosensory reception in Coccinellidae.SummaryThe predatory harlequin ladybird Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) has been widely released for classical and augmentative biological control programs of insect herbivores and is now distributed worldwide. Because of its invasive behavior and the threat it can pose to local biodiversity, this ladybird has been adopted as a model species for invasive biocontrol predators. A huge existing literature is available on this species. However, little is known about the mechanisms underlying H. axyridis smell and taste, even though these senses are important in this ladybird for courtship, mating and for locating suitable habitats for feeding and oviposition. Here we describe the first chemosensory gene repertoire that is expressed in the antennae of male and female H. axyridis. Our findings would likely represent the basis for future functional studies aiming at increasing the efficacy of H. axyridis in biological control or at reducing its populations in those areas where the ladybird has become a matter of concern due to its invasiveness.

Invasion history of Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) in Ecuador

Harmonia axyridis is a ladybird extensively used around the world for biological control of agricultural pests. However, it has become invasive in several countries, producing negative ecological and socio-economic impacts. Herein, we review the invasion history of the Harlequin Ladybird Harmonia axyridis (Pallas, 1773) in Ecuador. Although first reported in Ecuador in 2012, museum specimens date back to 2004 and it is currently established across the country, especially along the Andean region. Due to its invasive nature, further studies are urgently needed to evaluate possible impacts of H. axyridis on the Ecuadorian biodiversity and agroindustry.