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

Abstract

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.

Fungicides have transgenerational effects on Rhopalosiphum padi but not their endosymbionts

“…Additionally, we exposed aphids to fungicides at a single time point to ensure all aphids were at the same development stage but exposing aphids at multiple time points or at different life stages may have resulted in different findings. Past studies have demonstrated the impact of pesticides, and other stressors, can depend on the life stage exposure occurs 87,97,98 . Future work testing if endosymbionts are more vulnerable to fungicides (or other treatments) at a particular aphid life stage would be informative.…”

“…While our study is the first, to our knowledge, to show that fungicides have transgenerational effects on aphids, we can compare our findings to other studies that have shown multiple pesticides (including insecticides and herbicides) may have non-target effects on insects that manifest over multiple generations. [84][85][86] Transgenerational effects are rarely considered by farmers when they use fungicides or other pesticides, 87 but may provide greater pest management options. 81 For instance, if a single fungicide spray has deleterious impacts on a pest population that persists over generations, fewer applications of pesticides may be required to keep pest densities below economic threshold levels.…”

“…Past studies have demonstrated the impact of pesticides, and other stressors, can depend on the life stage exposure occurs. 87,97,98 Future work testing if endosymbionts are more vulnerable to fungicides (or other treatments) at a particular aphid life stage would be informative. It should also be noted that the commercial fungicides used here contain active ingredients mixed with adjuvants (e.g., surfactants), and these adjuvants may have contributed to the phenotypic effects detected; this could be further investigated by considering the effect of active ingredients independent of the formulations (i.e., using technical grade chemicals).…”

Life-table parameters, functional response, flight ability, and cross-generational effects of matrine demonstrate its safety to Hippodamia variegata (Coleoptera: Coccinellidae)

“…Farmers, however, often lack IPM expertise, and because of the advantages of simpleness and convenience, farmers tend to apply insecticides at higher than recommended concentrations and do so periodically rather than being based on pest density as revealed by scouting (Zhou et al 2014). Such pest control practices have increased the level of insecticide resistance of key pests and harmed natural enemy levels, which ultimately compromises pest management efficacy and agricultural resilience (Liu et al 2019, Yang et al 2019, Dai et al 2020, 2021). For example, Janssen and van Rijn (2021) showed that increasing insecticide use levels did not necessarily lower pest populations any further in the presence of effective natural enemies.…”

Sublethal Effects of Imidacloprid on Fecundity, Apoptosis and Virus Transmission in the Small Brown Planthopper Laodelphax striatellus

“…Sublethal effects of imidacloprid have been reported in many insects, e.g., affecting biological performances, changing enzyme activities or influencing gene expression [19][20][21]. Several studies suggested that the sublethal concentrations of imidacloprid negatively affected fecundity in exposed insects, such as Bemisia tabaci [22], Sogatella furcifera [23], Rhopalosiphum padi [20], Harmonia axyridis [24], and Ceratomegilla undecimnotata [25]. However, exposure to low concentrations of imidacloprid could benefit several insects, including Aphis glycines [26] and Myzus persicae [27].…”