Sublethal effects of tolfenpyrad on the development, reproduction, and predatory ability of Chrysoperla sinica

Toxic effects of the insecticide tolfenpyrad on zebrafish embryos: Cardiac toxicity and mitochondrial damage

Tolfenpyrad, a highly effective and broad-spectrum insecticide and acaricide extensively utilized in agriculture, presents a potential hazard to nontarget organisms. This study was designed to explore the toxic mechanisms of tolfenpyrad on zebrafish embryos. Between 24 and 96 h after exposure of the fertilized embryos to tolfenpyrad at concentrations ranging from 0.001 to 0.016 mg/L (96 h-LC50 = 0.017 mg/L), lethal effects were apparent, accompanied with notable anomalies including pericardial edema, increased pericardial area, diminished heart rate, and an elongated distance between the venous sinus and the arterial bulb. Tolfenpyrad elicited noteworthy alterations in the expression of genes pertinent to cardiac development and apoptosis, with the most pronounced changes observed in the cardiac development-related genes of bone morphogenetic protein 2b (bmp2b) and p53 upregulated modulator of apoptosis (puma). The findings underscore that tolfenpyrad induces severe cardiac toxicity and mitochondrial damage in zebrafish embryos. This data is imperative for a comprehensive assessment of tolfenpyrad risks to aquatic ecosystems, particularly considering the limited knowledge regarding its detrimental impact on aquatic vertebrates.

Sublethal effects of an indoxacarb enantiomer insecticide on Plutella xylostella caterpillar and Chrysoperla sinica predator

Plutella xylostella (L.) is a migratory species and an important insect pest of cruciferous crops worldwide, and Chrysoperla sinica (Tjeder) is a predaceous insect of agricultural and forest pests in the field. Indoxacarb has two enantiomers: (+)-S-indoxacarb and (-)-R-indoxacarb. This study was conducted to clarify the selective toxicity and sublethal effects of both enantiomers on P. xylostella and C. sinica. The (+)-S-indoxacarb isomer had greater acute toxicity to P. xylostella and C. sinica, while (-)-R-indoxacarb had less toxicity to P. xylostella and low toxicity to C. sinica. Lethal concentration 25 % (LC₂₅) of (+)-S-indoxacarb had significant effects on the development, population, and fecundity of P. xylostella and C. sinica. The LC₂₅ concentration of (-)-R-indoxacarb had a significant effect on the oviposition of P. xylostella. The field recommended concentration of (-)-R-indoxacarb significantly affected the pupal stage, adult survival rate, oviposition, and larval survival rate of C. sinica. Both enantiomers could significantly affect the search efficiency, successful attack rate, prey handling time, and maximum predation of C. sinica larvae, and the effects of (+)-S-indoxacarb alone were greater than those of (-)-R-indoxacarb. This study provided evidence of the different selective toxicity, sublethal effects of indoxacarb enantiomers on P. xylostella and C. sinica, which of the results could provide a basis for more rational use of indoxacarb in ecosystems.

Effects of tolfenpyrad exposure on development and response mechanism in the silkworm, Bombyx mori

Tolfenpyrad is a broad spectrum of insecticide that can effectively kill different types of pests, including Lepidoptera. However, due to improper use, the adverse effects of tolfenpyrad on beneficial or economic insects have not been well studied. In this study, we systematically investigated the toxic effect of sublethal tolfenpyrad on silkworms. Sublethal tolfenpyrad exposure can affect the body weight, developments days, cocooning rate, eclosion rate and pupation rate. To further study the response mechanism of silkworms to tolfenpyrad stimulation, we compared the different expression genes by transcriptome sequencing and verified them by qRT-PCR. We found that significant changes in the genes expression was involved in xenobiotics biodegradation and metabolism, immune system and digestive system after tolfenpyrad treatment. To further investigate the possible mechanisms by which intestinal microbia in the response to tolfenpyrad, we analysed the microbia changes in the midgut of silkworms by 16S rRNA gene sequencing. The results showed that the relative abundances of Enterobacter and Staphylococcus were increased whereas the Tyzzerella and Methylobacterium-Methylorubrum were decreased after tolfenpyrad stimulation. Taken together, these results indicated that low concentration of tolfenpyrad affect the growth and development of silkworms. Silkworms respond to the toxicity of tolfenpyrad by inducing immune and detoxification-related gene expression or altering microbial composition in the midgut.

Sublethal effects and reproductive hormesis of emamectin benzoate on Plutella xylostella

The diamondback moth (DBM), Plutella xylostella L., is an important pest of cruciferous vegetables, and population control mainly depends on chemical pesticides. Emamectin benzoate is a highly effective insecticide used for controlling DBM. However, it is unknown how the sublethal effects of low concentration residues of emamectin benzoate on DBM. So the population development sublethal effects of emamectin benzoate, at LC₅, LC₁₀, and LC₂₀ with concentrations of 0.014 mg/L, 0.024 mg/L and 0.047 mg/L, respectively, on adult DBM and their progeny were investigated in this study. The pupal weight, pupal period, female fecundity, and vitellin content of the F₀ DBM generation increased significantly compared to the control. And the single female oviposition number of DBM was increased by 20.21% with LC₂₀ treatment. The pupation rate, adult longevity and ovariole length of the treatment groups decreased significantly. The fecundity of DBM in the treatment groups increased, and this increased the population by a presumptive 13.84%. Treatment also led to the shortening of ovarioles and the reduction of egg hatching, and increased pupal weight in the F₁ generation. We concluded that the effects of sublethal/low concentration emamectin benzoate on the different life stages of DBM were variable, and the reproductive hormesis on DBM adults were attractive findings.