Efficacy of a long-lasting bifenthrin-treated net against horticultural pests and its compatibility with the predatory mite Amblyseius swirskii and the parasitic wasp Eretmocerus mundus

Selectivity of mycoinsecticides and a pyrethroid to the egg parasitoid Cleruchoides noackae (Hymenoptera: Mymaridae)

Plants of the genus Eucalyptus, cultivated in many countries, have great importance for the world economy. In Brazil, this culture occupies a total of 5.7 million hectares, but native and exotic insect pests can reduce its productivity. Thaumastocoris peregrinus Carpintero & Dellapé (Hemiptera: Thaumastocoridae), an exotic Australian pest, damages Eucalyptus plants. Biological control using the egg parasitoid Cleruchoides noackae Lin & Huber (Hymenoptera: Mymaridae), Heteroptera predators and entomopathogenic fungi, such as Beauveria bassiana and Metarhizium anisopliae, have potential for managing T. peregrinus. Chemical insecticides, including bifenthrin and acetamiprid + bifenthrin, also control this insect. The compatibility of chemical and biological control methods favors integrated pest management. The objective of this study was to evaluate the selectivity of commercial products based on B. bassiana, M. anisopliae and the chemical bifenthrin on the parasitoid C. noackae and its parasitism on T. peregrinus eggs. The selectivity test followed the standards recommended by the International Organization for Biological Control (IOBC). Beauveria bassiana has selectivity to parasitism as well as viability, but was slightly harmful to C. noackae adults; M. anisopliae was innocuous to adults and to the viability of the offspring of this parasitoid, but it reduced the parasitism rate; and bifenthrin did not show selectivity to this parasitoid.

Mobility and Dispersal of Two Cosmopolitan Stored-Product Insects Are Adversely Affected by Long-Lasting Insecticide Netting in a Life Stage-Dependent Manner

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Trogoderma variabile Ballion (Coleoptera: Dermestidae) are two stored-product insects that cause extensive damage to a variety of postharvest commodities. Long-lasting insecticide-incorporated netting (LLIN), commonly used to control vector-borne diseases in tropical regions, has only been recently studied in an agricultural setting. While prior research showed that LLIN was successful against stored-product beetles, little is known about differential susceptibility among stored-product insect life stages. The aim of this study was to evaluate LLIN efficacy against immature T. castaneum and T. variabile compared with adults. Movement and dispersal ability were evaluated after exposure to LLIN or an untreated, control netting. For the movement assay, video-tracking software recorded the postexposure effects of LLIN on distance traveled and velocity of the insects in 2-h trials. For the dispersal assay, insects were exposed to the netting then released into one end of a PVC pipe and allowed 48 h to disperse to a novel food patch located at the opposite end of the pipe. Our study found that movement and dispersal ability of T. variabile and T. castaneum are significantly reduced, often by multiple-fold, after LLIN exposure, with the larval stage of each species more tolerant to the insecticide netting than adults. These results indicate that LLIN is a promising tool for use in intercepting immigrating insects of different life stages in food facilities to protect stored products.

Environmentally relevant concentrations of bifenthrin induce changes in behaviour, biomarkers, histological characteristics, and the transcriptome in Corbicula fluminea

Bifenthrin (BF) is an insecticide that is commonly used to control agricultural and domestic pests and is widespread in aquatic environments. Although previous studies have found that BF is toxic to aquatic organisms, such a comprehensive study of the mechanism of toxic effects in bivalves is not common. In this study, to assess the toxic effects of BF on bivalves, adult Corbicula fluminea (C. fluminea) were exposed to 0, 1, 5, and 25 μg/L BF for 15 days. Transcriptome analysis revealed that BF exposure significantly altered the expression of genes involved in detoxification, antioxidation, and metabolism. Moreover, the ROS content and GST activity at 25 μg/L treatments were significantly increased (p < 0.05), and significant increases of MDA concentration and CAT activity were observed at 5 and 25 μg/L treatments (p < 0.05). However, AChE activity was markedly inhibited at 25 μg/L treatments (p < 0.05). In addition, vacuolation in the digestive tubules and the hemolytic infiltration of connective tissue were observed at all treatments, and the degeneration of the digestive tubule was observed at 5 and 25 μg/L treatments. In the behavioural assay, the siphoning behaviour of C. fluminea was significantly inhibited at 25 μg/L treatments (p < 0.05), whereas no significant change in burrowing behaviour was observed. Our findings suggested that BF exposure caused changes in detoxification, antioxidation, and metabolism pathways, biomarker activity or concentrations and histopathological characteristics, resulting in changes in behaviour. Therefore, our findings provide a basis for further evaluation of the toxicity of pyrethroid insecticides in bivalves.

Improving the compatibility of pesticides and predatory mites: recent findings on physiological and ecological selectivity

Integrated pest management relies upon the application of selective pesticides that do not hinder biological control. Phytoseiid mites represent an interesting case-study: they are amongst the most frequently used biological control agents and often are less affected by pesticides than their prey by natural tolerance or by developing resistance. The selectivity of a pesticide is determined by physiological processes that include metabolism, transport, and the affinity to the target-site. Genomic and transcriptomic studies start to elucidate the genetic and molecular mechanisms of differential toxicity in some phytoseiid species, such as a mutation in the sodium channel conferring pyrethroid resistance. Ecological selectivity is achieved by smart applications of pesticides and management practices that influence the persistence of phytoseiid mites on plants. Although modern pesticides often show lower acute toxicity, there is a need for robust assays and procedures that quantify lethal and sublethal effects, through different routes and times of exposure.

Toxicity of six insecticides to predatory mite Amblyseius cucumeris (Oudemans) (Acari: Phytoseiidae) in- and off-field

Amblyseius cucumeris (Oudemans) is a beneficial non-target arthropod (NTA) and a key predator of tetranychid mites in integrated pest management (IPM) programs across China. Evaluating the toxic effects of insecticides on such predatory mites is essential for the success and development of IPM. We tested six insecticides to determine the risk of neonicotinoid insecticide toxicity to predatory mites, using the 'open glass plate method' and adult female A. cucumeris in a "worst case laboratory exposure" scenario. A 48-h toxicity test was performed using the hazard quotient (HQ) approach to evaluate the risk of each insecticide. The LR₅₀ values (application rate that caused 50% mortality) of acetamiprid, thiamethoxam, imidacloprid, and dinotefuran were 76.4, 104.5, 84.9, and 224.6 g active ingredient (a.i.) ha^-1, respectively, with in-field HQ values of 0.40, 1.28, 0.49, and 0.82, respectively. The HQ values were lower than the trigger value of 2, and were consistent with off-field values. The risks of the four neonicotinoid insecticides to adult female A. cucumeris were acceptable in two exposure scenarios in field and off field. The 48-h LR₅₀ values for bifenthrin and malathion were 0.008 and 0.062 g. a.i. ha^-1, respectively, which were much lower than the recommended field application rates. The HQ values were much higher than the trigger values for both in- and off-field, indicating that the risks of these two insecticides were unacceptable. Bifenthrin and malathion posed an extremely high risk to the test species, and their use should be restricted to reduce risks to the field with augmentative releases of A. cucumeris.