Favorable compatibility of nitenpyram with the aphid predator, Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Fitness effect and transcription profile reveal sublethal effect of nitenpyram on the predator Chrysopa pallens (Neuroptera: Chrysopidae)

Although neonicotinoids are widely used and important insecticide, there are growing concerns about their effect on nontarget insects and other organisms. Moreover, the effects of nitenpyram (NIT), a second generation of neonicotinoid insecticides, on Chrysopa pallens are still unclear. Therefore, this study purposed to investigate the acute toxicity of NIT to C. pallens using the spotting method. To examine the potential effects of a sublethal dose of NIT (LD30 , 1.85 ng of active ingredient per insect) on C. pallens, we constructed the life tables and analyzed the transcriptome data. The life table results showed that the period of second instar larvae, adult pre-oviposition period and total pre-oviposition period were significantly prolonged after exposure to sublethal dose of NIT, but had no significant effects on the other instars, longevity, oviposition days, and fecundity. The population parameters, including the preadult survival rate, gross reproduction rate, net reproductive rate, the intrinsic rate of increase, and finite rate of increase, were not significantly affected, and only the mean generation time was significantly prolonged by NIT. Transcriptome analysis showed that there were 68 differentially expressed genes (DEGs), including 50 upregulated genes and 18 downregulated genes. Moreover, 13 DEGs related to heat shock protein, nose resistant to fluoxetine protein 6, and prophenoloxidas were upregulated. This study showed the potential effects of sublethal doses of NIT on C. pallens and provided a theoretical reference for the comprehensive application of chemical and biological control in integrated pest management.

Sublethal effects of acetamiprid and afidopyropen on Harmonia axyridis: insights from transcriptomics analysis

Evaluating the sublethal effects of insecticide is crucial for protecting and utilizing natural enemies. In this study, we determined the sublethal effects of acetamiprid and afidopyropen on Harmonia axyridis (Pallas) and explored the potential molecular mechanisms underlying these effects through transcriptomics analysis. The results showed that sublethal concentrations of acetamiprid significantly reduced the adult fecundity and longevity of F₀H. axyridis and decreased the survival time and survival rate of the F₁ generation. Sublethal concentrations of afidopyropen prolonged the developmental time of 4th instar larvae in the F₀ generation. Additionally, acetamiprid and afidopyropen treatments significantly decreased the predation of H. axyridis. Furthermore, transcriptome sequencing analysis revealed that several P450 and UGT genes expressed differently when H. axyridis were exposed to sublethal concentrations of acetamiprid and afidopyropen, suggesting that the differential expression of detoxifying genes might be involved in the response and detoxification metabolism of acetamiprid and afidopyropen in H. axyridis. Our findings demonstrate that sublethal concentrations of acetamiprid adversely influences the development and predation of H. axyridis, while afidopyropen has limited effects on H. axyridis. These results are helpful for protecting and utilizing natural enemies and guiding the scientific use of pesticides in the field.

Toxicity and Influence of Sublethal Exposure to Sulfoxaflor on the Aphidophagous Predator Hippodamia variegata (Coleoptera: Coccinellidae)

Hippodamia variegata (Goeze), the variegated ladybug, is a predator of many insect pests, especially aphids. Sulfoxaflor is a chemical insecticide that can be used to control many sap-feeding insect pests, for instance, plant bugs and aphids, as an alternative to neonicotinoids in different crops. To improve the combination of the H. variegata and sulfoxaflor in an IPM (integrated pest management) program, we studied the ecological toxicity of the insecticide to the coccinellid predator at sublethal and lethal doses. We examined the influence of sulfoxaflor on larvae of H. variegata using exposure doses of 3, 6, 12, 24, 48 (maximum recommended field rate (MRFR)), and 96 ng a.i. per insect. In a 15-day toxicity test, we observed decreased adult emergence percentage and survival, as well as an increased hazard quotient. The LD₅₀ (dose causing 50% mortality) of H. variegata due to sulfoxaflor decreased from 97.03 to 35.97 ng a.i. per insect. The total effect assessment indicated that sulfoxaflor could be grouped as slightly harmful for H. variegata. Additionally, most of the life table parameters were significantly decreased after exposure to sulfoxaflor. Overall, the results present a negative influence of sulfoxaflor on H. variegata when applied at the recommended field dose for controlling aphids in Greece, which demonstrates that this insecticide may only be employed with care when used in IPM programs.

Short exposure to nitenpyram pesticide induces effects on reproduction, development and metabolic gene expression profiles in Drosophila melanogaster (Diptera: Drosophilidae)

Although the toxicity of neonicotinoid insecticides has been demonstrated in several studies, the information on metabolism, behavior, and health risk remains limited and has raised concerns about its potential toxicity. Thus, in this study we assessed the effects of nitenpyram using different sublethal concentrations (one-third and one-tenth of the acute LC50 values) on various developmental and metabolic parameters from gene expression regulation in Drosophila melanogaster (model system used worldwide in ecotoxicological studies). As a result, nitenpyram sublethal concentrations prolonged the developmental time for both pupation and eclosion. Additionally, nitenpyram sublethal concentrations significantly decreased the lifespan, pupation rate, eclosion rate, and production of eggs of D. melanogaster. Moreover, the mRNA expression of genes relevant for development and metabolism was significantly elevated after exposure. Mixed function oxidase enzymes (Cyp12d1), (Cyp9f2), and (Cyp4ae1), hemocyte proliferation (RyR), and immune response (IM4) genes were upregulated, whereas lifespan (Atg7), male mating behavior (Ple), female fertility (Ddc), and lipid metabolism (Sxe2) genes were downregulated. These findings support a solid basis for further research to determine the hazardous effects of nitenpyram on health and the environment.

Monitoring and assessment of resistance to insecticides in the lacewing Chrysoperla carnea (Stephens)

Chrysoperla carnea (Stephens) is a key predator of several soft-bodied arthropods across various cropping ecosystems. Biological control is a prime strategy to reduce the harmful effects of pesticides on environment especially plants and arthropods. Collection of lacewings (Field Populations) was made during 2014 and repeated in 2016 from five different districts composed mainly by row and vegetable crops under conventional cropping system. For these populations, resistance level to four insecticides representing different mode of action was measured using topical treatment of 1^st-instar larvae with prepared dilutions of commercial formulation. The highest resistance levels were found for chlorfenapyr (100.86- to 423.78-fold) and indoxacarb (131.28- to 255.05-fold) in populations from all districts, while buprofezin and nitenpyram resistance was low to high and moderate to high, respectively. The levels of resistance to nitenpyram increased from 2014 to 2016 for populations of 3 out of 4 surveyed areas, while the susceptibility to buprofezin remained unchanged. Decrease in resistance levels for chlorfenapyr and indoxacarb in 2 years was marginal. These results suggest that field populations of C. carnea maintained resistance to buprofezin, chlorfenapyr, indoxacarb, and nitenpyram. Current outcomes support the fact that this bio-control agent could be a main nominee for mass release under judicious application of selective insecticides.

Responses of Harmonia axyridis (Coleoptera: Coccinellidae) to sulfoxaflor exposure

Harmonia axyridis is an important predator of several pest species and is part of many Integrated Pest Management (IPM) programs. To assess the risks of pesticide application to H. axyridis, we studied the effects of sulfoxaflor on H. axyridis larvae. At 72 h after treatment, the acute toxicity LR₅₀ was 311.9476 g a. i. ha^-1 by the residual contact method. This result indicated low-contact toxicity against second-instar H. axyridis larvae. The LR₅₀ of the F1 generation decreased from 69.96 to 36.41 g a. i. ha^-1 in a long-term toxicity test. The daily hazard quotient (HQ) for H. axyridis larvae lowered the safety threshold value in the first 5 d. However, the HQ values were greater than 2 during days 6-18 after sulfoxaflor treatments. We determined the No Observed Effect Application Rates of sulfoxaflor on the survival (<11.25 g a. i. ha^-1), duration of larval and pupal stages (45 g a. i. ha^-1), adult stage (90 g a. i. ha^-1), total pre-oviposition period, adult pre-oviposition period (45 g a. i. ha^-1), and reproduction (11.25 g a. i. ha^-1). Pupation, adult emergence, and eggs counts of H. axyridis were reduced after sulfoxaflor treatments. The predation ability and population demography parameters were significantly impaired by higher application rates. At 90 g a. i. ha^-1 or less, sulfoxaflor was slightly harmful to H. axyridis but a rate of 180 g a. i. ha^-1 was moderately harmful. These results demonstrated that sulfoxaflor is harmful to H. axyridis when applied at high application rates.

Compatibility of chlorantraniliprole with the generalist predator Coccinella septempunctata L. (Coleoptera: Coccinellidae) based toxicity, life-cycle development and population parameters in laboratory microcosms

Coccinella septempunctata is a common insect predator that provides biological control of many destructive arthropod pests. An assessment of the toxicity of pesticides to predators is a necessary component of Integrated Pest Management (IPM) strategies. In order to evaluate the risks of field insecticide application, we studied the influence of chlorantraniliprole on C. septempunctata larvae using different exposure doses. Chlorantraniliprole exhibited low contact toxicity against 2nd instar larvae of C. septempunctata with the LR₅₀ was 482.7063 g a.i. ha^-1 by after a 72-h exposure. In a long-term test, the LR₅₀ of chlorantraniliprole for C. septempunctata decreased from 88.97 to 58.22 g a.i. ha^-1, while the hazard quotient (HQ) values were below the threshold value of 2 during the entire observation period. This indicated a low toxicity risk from insecticide exposure. The total effect (E) suggested that chlorantraniliprole could be classified as harmless/slightly harmful to C. septempunctata below/at 200% of the MRFR (the manufacturer maximum recommended field rate) of 120 g a.i. ha^-1. We also determined no observed effect application rates (NOERs) of chlorantraniliprole on survival (7.5 g a.i. ha^-1), developmental time (15 g a.i. ha^-1) and fecundity (30 g a.i. ha^-1). Chlorantraniliprole significantly reduced the pupation rate, adult emergence, egg hatchability, and predation success. Population parameters, including R₀, r, λ, and T were significantly affected when C. septempunctata were treated with chlorantraniliprole at higher label rates. These results demonstrated that the use of chlorantraniliprole may reduce C. septempunctata population levels and the level of biological control provided by this species.

Sublethal and transgenerational effects of thiamethoxam on the demographic fitness and predation performance of the seven-spot ladybeetle Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Seven-spot ladybird beetles, Coccinella septempunctata L., are critical aphidophagous predators in the agricultural environment. Thiamethoxam, a neonicotinoid insecticide, is commonly used for controlling pests but impairs their natural enemies at the same time. To improve effective IPM (integrated pest management) strategies, we evaluated the sublethal and transgenerational effects of thiamethoxam on C. septempunctata. Our results showed that thiamethoxam at doses of 0.1 × LC₁₀ (0.053 mg L^-1) and LC₁₀ (0.53 mg L^-1) significantly reduced adult emergence, fecundity and fertility of the parental generation. In unexposed progeny (F₁) of thiamethoxam-exposed parents, at the two doses 0.1 × LC₁₀ and LC₁₀, the larval stage was prolonged, and total longevity was decreased by 18.76 and 24.46%, respectively. The higher concentrations (0.1 × LC₁₀ and LC₁₀) also decreased the fecundity by 33.74 and 46.56%, respectively, and the oviposition period by 19.67 and 25.01%, respectively. In addition, demographic parameters including the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R₀), and mean generation time (T) were significantly reduced when exposed to LC₁₀. Moreover, the predation activity of the F₁ generation was reduced by the transgenerational effects of LC₁₀. These results disclose negative influence of thiamethoxam at sublethal concentrations on this ladybird predator and its subsequent generation.