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

Abstract

Although employing nanocarriers for gene/drug delivery shows great potential in agricultural fields, the biotoxicity of nanocarriers is a major concern for largescale applications. Herein, we synthesized a cationic star polymer (SPc) as a pesticide nanocarrier/adjuvant to evaluate its safety against a widely used predatory ladybird (Harmonia axyridis). The application of SPc at extremely high concentrations nearly did not influence the hatching of ladybird eggs but it led to the death of ladybird larvae at lethal concentration 50 (LC 50 ) values of 43.96 and 19.85 mg/mL through the soaking and feeding methods, respectively. The oral feeding of SPc downregulated many membrane protein genes and lysosome genes significantly, and the cell membrane and nucleus in gut tissues were remarkably damaged by SPc application, revealing that the lethal mechanism might be SPc-mediated membrane damage. Furthermore, the oral feeding of SPc increased the relative abundance of Serratia bacteria in ladybird guts to result in bacterial infection. Coapplication of ladybird and SPc-loaded thiamethoxam/matrine achieved desired control efficacies of more than 80% against green peach aphids, revealing that the coapplication could overcome the slow-acting property of ladybirds. To our knowledge, this is the first attempt to investigate the polymer-mediated lethal mechanism toward natural enemies and explore the possibility of coapplying SPc-loaded pesticides and natural enemies for pest management.

Nanocarrier-Loaded Imidaclothiz Promotes Plant Uptake and Decreases Pesticide Residue

“…As expected, the SPc exhibited no obvious toxicity toward aphids, confirming its negligible stomach toxicity. Extremely high concentrations of SPc can down-regulate many membrane protein genes and lysosome genes, leading to the damage of cell membrane in gut tissues of ladybirds [ 49 ]. Based on our current data, the SPc exhibited an excellent biocompatibility.…”

A Preparation Method of Nano-Pesticide Improves the Selective Toxicity toward Natural Enemies

“…Thus, the CNAP/SPc complex or CNAP alone was relatively safer toward O. sauteri compared to neonicotinoid insecticides. The SPc-loaded matrine and predatory ladybirds have been co-applied to suppress the green peach aphids, which can overcome the slow-acting property of ladybirds [ 34 ]. The co-application of CNAP/SPc complex and O. sauteri may be suitable for efficient control of WFTs, which will be further tested for reducing the pesticide application.…”

“…Thus, the SPc-loaded pesticides have the potential to overcome agricultural, forestry and environmental challenges. Although the working concentration of SPc is relatively safe to predatory ladybirds, the safety and selective toxicity of SPc-loaded pesticides or other nanopesticides toward predators remain unclear [34]. There are two important issues related to the selective toxicity of SPc-loaded pesticides: (1) whether the SPc increases the toxicity of pesticides against both target pests and non-target predators with the enhancement of broad-spectrum bioactivity, and (2) whether the application of SPc changes the selective toxicity of pesticides.…”

Combination of a nanocarrier delivery system with genetic manipulation further improves pesticide efficiency: a case study with chlorfenapyr

“…47,53,54 For example, the median lethal concentration (LC 50 ) of oral feeding SPc toward ladybirds was 9925 times that of the SPc's working concentration, indicating that the biosafety of SPc itself might not be a serious issue at its working concentration. 54 The side chains of SPc are constructed with 2-N-(dimethyl aminoethyl) methacrylate (DMAEMA) polymers which are biodegradable, 55 suggesting that they might not possess significant environmental risk. Nevertheless, whether and how SPc could be degraded in insects and in the environment need to be further explored.…”