Lethal and behavioral sublethal side effects of thiamethoxam on the predator Harmonia axyridis

Abstract

Thiamethoxam (TMX) is one of the most effective neonicotinoid insecticides for the control of green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), and various side effects can be expected in its natural enemies. The multicolored Asian lady beetle or harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is an important predator against M. persicae in greenhouses and fields. In this study, we evaluated the toxicity of TMX to H. axyridis and the effect on the functional response of this predator to M. persicae through three routes of exposure. Acute toxicity bioassays indicated that LC50 values of TMX on H. axyridis through direct residual contact (‘contact’), systemic application (‘systemic’), and leaf‐dip treatment (‘leaf‐dip’) were 18.99, 21.26, and 15.39 mg a.i. l−1, respectively. The hazard quotient indicated a potential hazard of this agrochemical regardless of the exposure routes. The mortality caused by the lowest rate, 2 mg a.i. l−1, was not significantly different compared with the control group. For the three routes of sublethal TMX exposure, the type‐II functional response was a good fit to the prey consumption of H. axyridis. Predation was most affected by leaf‐dip treatment, followed by contact and systemic treatments, which had similar effect. For all exposure routes, the predation capacity of the predator recovered quickly after transfer to untreated cabbage leaves. Thiamethoxam applied systemically was the least toxic to H. axyridis and did not affect the functional response of the predator. However, the sublethal effects of TMX through both contact and leaf‐dip application may reduce the population growth of H. axyridis and consequently impair the biological control of M. persicae by this predator. These results illustrate that the assessment of potential effects of TMX on H. axyridis is crucial to develop effective integrated pest management programs for M. persicae in China.

Biotoxicity Evaluation of a Cationic Star Polymer on a Predatory Ladybird and Cooperative Pest Control by Polymer-Delivered Pesticides and Ladybird

“…A previous study has demonstrated that the sublethal effects of thiamethoxam reduced the population growth of H. axyridis and consequently impaired the biological control of aphids. 32 Thiamethoxam at doses of 0.053 and 0.53 mg/mL can also reduce adult emergence, fecundity, and fertility of seven-spot ladybird beetles. 33 In the current study, although the application of two pesticide/SPc complexes decreased the survival rate of ladybird larvae, their application exhibited no influence on egg hatching (Figure 6).…”

“…Meanwhile, pesticide application usually decreases the population density of natural enemies in field. 32,33 To obtain comparable control efficacy, the application amount of pesticide can be decreased with the help of a polymer, and whether polymer-loaded pesticides and natural enemies can be coapplied is an interesting topic.…”

Toxicity, Sublethal and Low Dose Effects of Imidacloprid and Deltamethrin on the Aphidophagous Predator Ceratomegilla undecimnotata (Coleoptera: Coccinellidae)

“…At the same time, the predators redirect energy towards detoxifying the insecticide instead of growth and development [56]. Further research is required in pesticide risk-assessment evaluation schemes to determine the sublethal effects on predatory behavior (e.g., functional response) [24,25,33,57].…”

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

“…To the best of our knowledge, several studies on acute toxicity of imidacloprid and sulfoxaflor to non-target natural enemies such as ladybeetle predators have been conducted [49,59]. However, the potential long-term influence of imidacloprid and sulfoxaflor on H. axyridis has been scarcely investigated [59]. Hence, we have explored the transgenerational impact of low lethal concentrations of sulfoxaflor and imidacloprid on H. axyridis.…”