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The cosmopolitan pest Aphis gossypii (Glover) causes considerable economic losses on various crops by its feeding damage and transmitting diseases around the world. Flupyradifurone is a novel butenolide pesticide; its toxicity on A. gossypii parent generation (F0) was estimated following treatment with LC25 concentration for 48 h. The adult longevity and fecundity of the F0 individuals treated by flupyradifurone showed no significant decrease in comparison with the control. Life table method was used to evaluate the sublethal effects on progeny population (F1). Results showed that the development time of the fourth instar and the preadult as well as the total pre-reproductive period were significantly prolonged, while their fecundity was significantly decreased compared with the control. Additionally, the intrinsic rate of increase (r), the finite rate of increase (λ), and the net reproductive rate (R0) of F1 were all significantly lower in the group treated by LC25 than in the control group.These results reveal that the sublethal concentration of flupyradifurone could suppress the population growth of A. gossypii and indicate that this novel insecticide may be as a useful tool in pest management.

The cabbage aphid, Brevicoryne brassicae (L.), is one of the major insect pests of cole crops in Iran. In most instances outbreaks are normally kept under control by application of insecticides. In this study, the sublethal effects (LC30) of three insecticides, acetamiprid, buprofezin, and thiamethoxam-lambda cyhalothrin, (TLC) were evaluated on the population growth rate of the progeny of insecticide-treated cabbage aphid adults. The age-stage, two-sex life table method was used to analyze the collected data. The results indicated that the insecticide applications affected the duration of the preadult period, their survival, reproduction, life span/longevity, and consequently, the population growth rate of the F1 generation. The indicators of the greatest sublethal effects were noted in the progeny of the TLC-treated adults. These included the lowest net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and the longest mean generation time (T). The highest values of r, λ, R, and the lowest value of T occurred in the control group followed by, in order, the acetamiprid and buprofezin groups. These research findings will be useful in the development and implementation of future aphid management programs.

The lethal heat treatment dose (time and temperature) for the prepupal life stage of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), emerald ash borer (EAB), was determined through an in vitro application using a carefully calibrated heat treatment apparatus.The lethal and sublethal effects of heat on A. planipennis prepupae were assessed through a ramped heat delivery application, simulating industrial kilns and conventional heat chamber operations, for treatments combining target temperatures of 54 °C, 55 °C, and 56 °C, and exposure durations of 0 min (i.e., kiln temperature ramp only), 15 min, or 30 min. Prepupal EAB larvae did not survive exposure to 56 °C for 15 min or longer, or to 55 °C for 30 min. Sublethal effects were observed for all other treatments. Sublethal effects included delayed development and failure to complete the pupal and adult life stages.

Spiders are key predators in many agroecosystems, including orchards. Despite the importance of spiders in biological control, pesticide nontarget effects on this group are poorly described. This is especially true for herbicides, which spiders frequently encounter as they move between the ground cover and tree canopy. We sought to determine the nontarget effects of seven herbicides used in orchards on three species of spiders that are commonly found in Washington state (USA) orchards: Pelegrina aeneola (Curtis) (Araneae: Salticidae), Philodromus cespitum (Walckenaer) (Araneae: Philodromidae), and Phanias watonus (Chamberlin & Ivie) (Araneae: Salticidae). Immature spiders were collected from orchards and used in laboratory assays. Single spiders were placed in vials with dried herbicide residues and mortality was evaluated after 1, 2, and 5 d. We also evaluated herbicide impacts on prey consumption rates and on spider movement using motion-tracking software. Only oxyfluorfen caused significant spider mortality. P. cespitum seemed to be less acutely sensitive to oxyfluorfen than the two salticid species. Several herbicide treatments significantly increased locomotion in P. cespitum, whereas rimsulfuron numerically decreased movement of P. aeneola. Sulfonylurea herbicides (rimsulfuron, halosulfuron) decreased prey consumption of P. aeneola. Our work indicates that although spiders may be less acutely sensitive to some pesticides than beneficial insects, they can be affected by sublethal effects of herbicides. Future work should determine if herbicide applications impact spider abundance in the field and reduce biological control services. In general, more work is needed on the impacts of herbicides on natural enemies. Graphical Abstract

The small brown planthopper (Laodelphax striatellus (Fallén), Hemiptera: Delphacidae), is an important agricultural pest of rice, and neonicotinoid insecticides are commonly used for controlling L. striatellus. However, the sublethal effects of thiamethoxam on L. striatellus remain relatively unknown. In this study, an age-stage life table procedure was used to evaluate the sublethal effects of thiamethoxam on the biological parameters of L. striatellus. Additionally, activities of carboxylesterase, glutathione S-transferase, and cytochrome P450 monooxygenase in the third instar nymphs were analyzed. The results indicated that the survival time of F0 adults and the fecundity of female adults decreased significantly after the third instar nymphs were treated with sublethal concentrations of thiamethoxam (LC15 0.428 mg/liter and LC30 0.820 mg/liter). The developmental duration, adult preoviposition period, total preoviposition period, and mean generation time of the F1 generation increased significantly, whereas the fecundity of the female adults, intrinsic rate of increase (ri), and finite rate of increase (λ) decreased significantly. The oviposition period was significantly shorter for the insects treated with LC30 than for the control insects. Neither sublethal concentrations had significant effects on the adult longevity, net reproduction rate (R0), or gross reproduction rate (GRR) of the F1 generation. The activities of carboxylesterase, glutathione-S-transferase, and cytochrome P450 monooxygenase increased significantly after the thiamethoxam treatments. These results indicate that sublethal concentrations of thiamethoxam can inhibit L. striatellus population growth and enhance detoxification enzyme activities.

Grapholita molesta is one of the most important fruit pests worldwide. Abamectin is a biological pesticide frequently used to control fruit borers like G. molesta in part owing to its translaminar properties. In this study, we characterized the toxicity of abamectin to G. molesta larvae using the diet incorporation method. The sublethal effects of abamectin on the development, reproduction, detoxification enzyme activity, and related gene expression of G. molesta were assessed. The results showed that the LC20 and LC50 values of the insecticide against G. molesta 72 h post-treatment were 1.17 mg L–1 and 5.85 mg L–1, whereas the LC20 and LC50 values 96 h post-treatment were 0.34 mg L–1 and 3.63 mg L–1. When compared to the control, sublethal concentrations of abamectin 1) significantly increased the mortality of the larvae, prepupae, and pupae of G. molesta, 2) prolonged the duration of 3rd to 5th instar larva, prepupal and pupal periods, 3) shortened the longevity of adults, and 4) reduced female fecundity. The enzymatic activity of glutathione S-transferase (GST) varied significantly after exposure to sublethal concentrations of abamectin, but the cytochrome P450 monooxygenases and carboxylesterase activity were not significantly affected. Thirteen of the 25 GST genes were significantly upregulated under different sublethal concentrations of abamectin. The combined findings increase our understanding of the effects of abamectin on G. molesta and the potential role of GSTs in the metabolic interactions of abamectin in this pest, and have applications for more rational and effective use of abamectin to control G. molesta.

The green peach aphid, Myzus persicae (Sulzer), is an important insect pest of many crops around the world. Pesticide-induced hormesis may be an alternative mechanism for pest resurgence. In this study, life table parameters were applied to the estimation of sulfoxaflor-induced hormesis of adult M. persicae following 2-d LC25 concentration exposure. Leaf-dip bioassays showed that the sulfoxaflor possessed high toxicity against M. persicae, with an LC50 of 0.059 mg/liter. The results indicated that the exposure of the parent generation of M. persicae to sublethal sulfoxaflor induced increase in reproduction and prolongation of immature development duration in the first progeny generation. Both R0 and GRR of aphids for treatment group were significantly higher than for the control in F1 generation, and the mean generation time was significantly postponed in treated group. These results suggest a hormesis induced by lower concentration of sulfoxaflor in M. persicae. It would be useful for assessing the overall effects of sulfoxaflor on M. persicae.

Spinetoram, a spinosyn insecticide is used to manage lepidopteran pests, including diamondback moth, Plutella xylostella. In addition to determining the lethal effects, identifying low and/or sublethal effects of an insecticide is crucial to understanding the total impact of an insecticide. We assessed the low lethal and sublethal effects of spinetoram on two successive generations of P. xylostella. The initial bioassay results showed that spinetoram exhibited high toxicity against P. xylostella with an LC50 of 0.114 mg L−1 after 48 h exposure. The low lethal (LC25) and sublethal (LC10) concentrations of spinetoram showed significant reduction in pupation rate, pupal weight and adult emergence. The fecundity of F1 generation was significantly lower in LC25 (117.85 eggs/female) and LC10 (121.34 eggs/female) treated group than untreated control (145.32 eggs/female). The intrinsic rates of increase (r) was significantly lower (r = 0.1984 day−1) in spinetoram treated P. xylostella F1 progeny compared to untreated control (r = 0.2394 day−1). Our results suggest that LC10 and LC25 concentration of spinetoram might affect P. xylostella population growth by reducing its survival, development, and reproduction.

The spider mite, Tetranychus pueraricola (Ehara & Gotoh; Acari: Tetranychidae), is a serious pest in agriculture and horticulture. Application of chemical pesticides is the main mode of this pest control. Due to pesticide residues and resistance-induced resurgence of pests, there is a need to discover alternatives for spider mite management. GC16 comprises a mixture of calcium chloride (CaCl2, 45%) and lecithin (55%), which was recently found to have acaricidal properties. We evaluated the sublethal effects of GC16 on T. pueraricola using life table and enzyme [catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), carboxylesterase (CarE), glutathione S-transferases (GST), and Ca2+-ATPase (Ca2+-ATP)] activity assays. The results showed that fecundity of T. pueraricola increased at LC30 but decreased at LC50 of GC16. The intrinsic rate of increase (r) of T. pueraricola decreased under the LC30 and LC50 of GC16. GC16 concentration and exposure time significantly influenced the activities of CAT, POD, CarE, GST, and Ca2+-ATP in adult mites. Twelve hours later after the treatment, GST and Ca2+-ATP activities were significantly inhibited by LC30 but enhanced by LC50. Moreover, the demographic parameter r and enzyme activities were negatively correlated. In sum, sublethal amounts of GC16 had an adverse effect on mites, and there was a trade-off between developmental performance and physiological enzyme activity of mites under GC16 stress, and GC16 showed an acaricidal potential for T. pueraricola. This work provides guidance for the application of GC16 to control T. pueraricola. Graphical Abstract

The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is an agricultural pest that seriously infests many crops worldwide. This study used electrical penetration graphs (EPGs) and life table parameters to estimate the sublethal effects of cyantraniliprole and imidacloprid on the feeding behavior and hormesis of M. persicae. The sublethal concentrations (LC30) of cyantraniliprole and imidacloprid against adult M. persicae were 4.933 and 0.541 mg L−1, respectively. The feeding data obtained from EPG analysis indicated that the count probes and number of short probes (<3 min) were significantly increased when aphids were exposed to LC30 of imidacloprid-treated plants. In addition, the phloem-feeding behavior of M. persicae was significantly impaired on fed tobacco plants treated with cyantraniliprole and imidacloprid at LC30. Analysis of life table parameters indicated that the growth and reproduction of F1 generation aphids were significantly affected when initial adults were exposed to LC30 of cyantraniliprole and imidacloprid. The nymphal period, female longevity, total preoviposition period, and mean generation time were significantly prolonged when initial adults were exposed to LC30 of imidacloprid. By comparison, these parameters were prolonged but not significantly in the cyantraniliprole treatment. The fecundity and gross reproductive rate were significantly increased in the treated groups. Similarly, the net reproductive rate was greater in the treated group than the control group. Our results indicate that treatment with LC30 of imidacloprid and cyantraniliprole would lead to a hormetic response of M. persicae, with higher likelihood of occurrence when initial adults were exposed to LC30 of cyantraniliprole.