Lethal and Sublethal Toxicity of Insecticides to the Lacewing Ceraeochrysa Cubana

Bees as environmental and toxicological bioindicators in the light of pesticide non-targeted exposure

Pesticides have a significant impact on the environment, harming valuable non-target organisms like bees. Honeybees, in particular, are ideal bioindicators of pesticide exposure due to extensive research on how pesticides affect their behavior, immunity, development, biomolecules, and detoxification. However, wild pollinators are less studied in terms of pesticide exposure, and their inclusion is essential for a comprehensive risk assessment. Additionally, food chain organisms, such as the Asian hornet, could serve as indicators of pesticide bioaccumulation. Addressing gaps in honeybee toxicology, understanding the limitations, and exploring the role of wild pollinators and insects as complementary indicators, along with advancements in risk assessment methodologies, could enhance predictive models. These models would help anticipate environmental pesticide impacts while reducing the need for costly, time-consuming research.

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.

Evaluation of the Toxicity and Sublethal Effects of Acetamiprid and Dinotefuran on the Predator Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae)

Neonicotinoid insecticides affect the physiology or behavior of insects, posing risks to non-target organisms. In this study, the effects of sublethal doses of two neonicotinoid insecticides, acetamiprid and dinotefuran, against Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae) were determined and compared. The results showed that acetamiprid and dinotefuran at LD₁₀ (8.18 ng a.i. per insect and 9.36 ng a.i. per insect, respectively) and LD₃₀ (16.84 ng a.i. per insect and 15.01 ng a.i. per insect, respectively) significantly prolonged the larval stages and pupal stages (except acetamiprid LD₁₀), compared to control. In addition, acetamiprid and dinotefuran at LD₃₀ significantly prolonged the adult preoviposition period (APOP) and total preoviposition period (TPOP). In contrast, the two insecticides at LD₁₀ and LD₃₀ had no significant effect on the longevity, fecundity, reproductive days, preadult survival rate (%), intrinsic rate of increase (r), net reproductive rate (R₀), and finite rate of increase (λ). These results provide a theoretical basis for the rational use of these two insecticides and the utilization and protection of C. pallens.

Toxicity of Varronia curassavica Jacq. Essential Oil to Two Arthropod Pests and Their Natural Enemy

This study aimed to evaluate the toxicity of the Varronia curassavica Jacq. essential oil to two cosmopolitan and polyphagous pest species, the two-spotted spider mite (Tetranychus urticae Koch) and the green aphid (Myzus persicae Sulzer). Additionally, we tested the essential oil toxicity to a generalist predatory insect, the green lacewing Ceraeochrysa cubana Hagen. The treatments consisted of four essential oil concentrations (0.25, 0.5, 0.75 and 1.0%) and one control (Tween® 80 + water). At 0.75% concentration, the V. curassavica essential oil caused the highest mortalities for both pests. The concentration of 1.0% of the essential oil interfered mainly in the rates of oviposition and egg hatching and caused a decrease in the instantaneous population growth rate (r_i) of T. urticae. Survival of the C. cubana was not affected by the highest tested concentration of the essential oil (1%). Tested concentrations V. curassavica essential oil were toxic to T. urticae and M. persicae, but not to the predator C. cubana.

Susceptibility of Chrysoperla externa (Hagen, 1861) (Neuroptera: Crysopidae) to insecticides used in coffee crops

The coffee crop hosts pests such as mites, mealybugs, and aphids which serve as food for the predator Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae). The preservation of this chrysopid in coffee agroecosystem is very important to achieve sustainability of this agricultural sector, and can be obtained by applying low toxicity insecticides. The present study aimed to evaluate the susceptibility of C. externa to azadiracthin, chlorpyrifos, ethiprole and teflubenzuron. Predator eggs, third instar larvae, pupae and adults were exposed to insecticides by Potter tower spraying. When evaluating exposure of C. externa eggs we observed that chlorpyrifos, ethiprole and teflubenzuron reduced larvae hatching, while azadiracthin prolonged first instar duration. Meanwhile, the exposure of third instar larvae to chlorpyrifos and ethiprole caused mortality of all insects after 72 h, while azadiracthin prolonged the larval development time; we also observed that no compound allowed the formation of adults. After pupae were exposed to chlorpyrifos and teflubenzuron, it was observed a reduction on the emergence of adults, while the longevity of adults from these pupae and the evaluated reproductive parameters were reduced by all insecticides. For the bioassay with adults, chlorpyrifos, ethiprole and teflubenzuron reduced the longevity of insects, while the reproductive parameters evaluated were negatively affected after exposure to azadiracthin and teflubenzuron. It was concluded that all insecticides negatively affected at least one biological characteristic of the predator in at least one of the insect's developmental stages, requiring further research in semi-field and field conditions to prove its toxicity.

Selectivity of Entomopathogenic Fungi to Chrysoperla externa (Neuroptera: Chrysopidae)

Simple Summary

Agricultural crop systems have adopted integrated management as a model of success in pest control; however, chemical control is still prioritized. The use of pesticides incorrectly and excessively has provided a reduction in natural enemies, selection of resistant populations and resurgence of pests. Chrysoperla externa is a predator found in several regions in Brazil that preys on different pest insects. Entomopathogenic fungi Beauveria and Metarhizium also stand out for causing epizootics on pests. Both predators and entomopathogens can simultaneously act as pest control; thus, verifying the selectivity of entomopathogenic fungi to predators increases the potential for biological control through synergism and conservation of natural enemies in the agroecosystem. Considering the control potential of these different biological control agents, in this study we evaluated the selectivity of Beauveria bassiana, Metarhizium anisopliae and Metarhizium rileyi to the larvae of this predator. The results provide evidence that the biological development of larvae of C. externa is not influenced by the entomopathogenic fungus. These species of fungi can be recommended, aiming at a management of populations of arthropod pests, with low effect on C. externa when it is present in the agrosystem.

Abstract

We aimed to evaluate the selectivity of entomopathogenic fungi to larvae of Chrysoperla externa (Neuroptera: Chrysopidae). For this purpose, Beauveria bassiana (strain ESALQ PL63), Metarhizium anisopliae (strain ESALQ E9) and Metarhizium rileyi (strain UFMS 03) were assessed at different concentrations (1 × 10⁷, 1 × 10⁸ and 1 × 10⁹ conidia mL⁻¹). The control treatment consisted of distilled water and Tween80 0.01. The treatments were applied with a Potter spray tower using two different methodologies: direct application (DA) and dry film (DF). Up to 96 h after application, no treatment provided a larval mortality above 3%. After 120 h, only B. bassiana induced significant mortality in all instars, with rates of 26%, 17% and 10% for first, second and third instar larval periods, respectively. There was no difference regarding to the application method or concentration of conidia. The percentage of individuals that revealed changes in the length of the larval and pupal periods varied among different treatments with entomopathogenic fungi and control treatments, application methodologies and concentrations. Despite B. bassiana revealing a higher mortality than M. anisopliae and M. rileyi on larvae of C. externa, these three entomopathogenic fungi may be used in association with C. externa for sustainable pest management.

Acute lethal and sublethal effects of four insecticides on the lacewing (Chrysoperla sinica Tjeder)

The lacewing, Chrysoperla sinica, is an important predatory insect, which plays an important role in the integrated pest management of agroforestry pests. However, the extensive use of insecticides negatively affects C. sinica. The acute toxicity, risk level, and, sublethal effects on growth and production, predation ability, protective enzyme activity and genotoxicity of four insecticides: indoxacarb, emamectin benzoate, imidacloprid and lambda-cyhalothrin to C. sinica were studied. The results showed that all four insecticides had lethal toxicity to larvae of C. sinica. Among them, emamectin benzoate had the highest toxicity with LC₅₀ value of 7.41 mg/L. The insecticides also had different effects on the growth and reproduction of C. sinica, of which lambda-cyhalothrin had the greatest impacts. Even at a very low LC₁ concentration (3.37 mg/L), it had strong impacts on the growth, reproduction and predatory ability of C. sinica. The four insecticides also caused a decrease in the predatory ability of the lacewing, of which lambda-cyhalothrin had the greatest effect. During the larval stage, the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were significantly decreased by the four insecticides. At the pupal and adult stages, the effects of the four insecticides on the activities of protective enzymes were different, and the activities of SOD, CAT and POD decreased or increased. Indoxacarb and lambda-cyhalothrin exposure induced DNA damage in the haemocytes of C. sinica and produced obvious genotoxicity. These results provide important scientific basis for the rational use of these insecticides and the protection and utilization of lacewing.

Non-target toxicity of nine agrochemicals toward larvae and adults of two generalist predators active in peach orchards

Chrysoperla externa and Coleomegilla quadrifasciata are important biological control agents in peach orchards. However, orchard management with these predatory insects is viable only by using selective agrochemicals. The objective of this study is to evaluate the toxicity of nine agrochemicals used in peach orchards in larval and adult stages of the C. externa and C. quadrifasciata in laboratory conditions. The bioassays followed the methodologies proposed by the International Organization for Biological and Integrated Control (IOBC). Larvae and adults of C. externa and C. quadrifasciata were exposed to the dry residues of these products. Lethal and sublethal effects were evaluated in bioassays with the larval and adult stages of both predators. The agrochemicals were classified according to the IOBC guidelines. The insecticide chlorantraniliprole was harmless (class 1) to the larval stage of C. externa and C. quadrifasciata. Azadirachtin, copper 25% + calcium 10%, and deltamethrin were harmless to the adult stage of both insect species. The organophosphates fenitrothion and malathion were harmful (class 4) to both species in the larval and adult stages and should not be used in peach orchards. Therefore, this study demonstrates the importance of toxicity and the lethal and sublethal effects of these agrochemicals to better determine their compatibility with IPM in peach production.

Pest Management Systems and Insecticide Tolerance of Lacewings (Neuroptera: Chrysopidae)

Lacewings (Neuroptera: Chrysopidae) are part of the beneficial fauna found in citrus orchards under both organic and conventional pest management. Due to their importance, knowledge about susceptibility of these predators to insecticides is a key element for their use as biological control agents. We studied the inter- and intraspecific susceptibility of the following lacewing species to bifenthrin, chlorpyrifos, and imidacloprid: Ceraeochrysa cincta (Schneider) (Neuroptera: Chrysopidae), Ceraeochrysa cubana (Hagen), Ceraeochrysa paraguaria (Navás), and Chrysoperla externa (Hagen). Different concentrations of these insecticides were sprayed on first instar larvae of these lacewing species from six orchards (three organic and three conventional), and LC50s were estimated. Development and reproduction of the most common lacewing, C. cincta, from both organic and conventional management systems were also studied. Lacewings from conventional management areas do not always have greater tolerance to insecticides. Chrysoperla externa was the most susceptible species to insecticides. Ceraeochrysa cincta displayed the highest LC50 and its populations from the conventional system showed lower egg hatching but shorter egg and larval developmental time. Adults collected from orchards managed conventionally lived longer, exhibited a higher population growth rate and a reduced doubling time. Ceraeochrysa cincta was the more tolerant species to insecticides better coping with systems that rely on chemical control as the main pest management tactic used.