Fungicides affect Japanese beetle Popillia japonica (Coleoptera: Scarabaeidae) egg hatch, larval survival and detoxification enzymes

Fungicides modify pest insect fitness depending on their genotype and population

Fungicides are the most sold pesticide group, with an 8% increase in sales in Europe within the last decade. While adverse short-term fungicide effects on non-target insect species have been reported, the long-term effects and their impact on fitness are unclear. As the effects may depend on both the fungicide and the genetic background of the species, we investigated the effects of the commonly used fungicide, fluazinam, on the Colorado potato beetle's life history traits, and whether the effects were dependent on a previously characterized insecticide resistance mutation (S291G in acetylcholinesterase-2 gene) in different populations. Our findings show that fungicide exposure can have both negative and positive, long-lasting effects on beetles, depending on the parental insecticide resistance status and population. In the Belchow population, individuals carrying resistance mutation had higher survival, but they produced offspring with lower egg-hatching rates. While, in the Vermont population, fungicide exposure increased the body mass and offspring quality in the beetles carrying resistance mutation but did not affect the beetles' survival. Our results suggest that commonly used fungicides can have both negative and positive effects on pest insects' life-history, however, their impact may differ depending on the population and parental genetic background.

Toxicity and risk assessment of nine pesticides on nontarget natural predator Harmonia axyridis (Coleoptera: Coccinellidae)

BACKGROUND

Harmonia axyridis (Coleoptera: Coccinellidae) is a beneficial predatory arthropod in the agricultural ecosystem. For the success and development of integrated pest management strategies, it is essential to assess the toxicity risks of commonly used pesticides to nontarget arthropods.

RESULTS

The glass tube residue method was used to determine the risk of nine pesticides to H. axyridis after second-instar exposure. To assess the potential risk of the selected pesticides, the pre-adult LR₅₀ values were calculated by the hazard quotient (HQ) method. The LR₅₀ (application rate causing 50% mortality) values of imidacloprid, dinotefuran, thiamethoxam, acetamiprid, bifenthrin, and dimethoate were 0.44, 0.82, 0.10, 0.05, 0.04, and 0.21 g a.i. ha^-1 , respectively, showing unacceptable risk to H. axyridis after exposure to in and off field. However, emamectin benzoate and two fungicides, tebuconazole and myclobutanil, posed a low risk to H. axyridis and their HQ values were less than the trigger value of 5.

CONCLUSIONS

The four neonicotinoid insecticides (imidacloprid, dinotefuran, thiamethoxam, and acetamiprid), pyrethroid bifenthrin, and organophosphorus dimethoate showed a high risk to H. axyridis. Emamectin benzoate, tebuconazole, and myclobutanil showed a low risk to H. axyridis under both exposure scenarios. The results provide critical scientific evidence to guide future regulation of pesticide management practices and protection of nontarget arthropods like H. axyridis. © 2022 Society of Chemical Industry.

Gradual Decline of Japanese Beetle (Coleoptera: Scarabaeidae) Populations in Michigan Follows Establishment of Ovavesicula popilliae (Microsporidia)

The purpose of this research was to document the incidence of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), infection by the microsporidian pathogen, Ovavesicula popilliae Andreadis & Hanula (Microsporida: Pleistophoridae) while monitoring Japanese beetle populations at nine golf courses in Michigan from 1999 to 2018. We also compared the current distribution of the pathogen in Michigan to the known distribution in 1999. Beetles were sampled a total of seven different years, in three time periods: 1999-2000, 2005-2007, and 2015-2018. At these nine golf courses, O. popilliae infection rates of adults increased from 0.39% in 2000 to 29.5% in 2018, while Japanese beetle adult populations declined 73.2%, and Japanese beetle larval density declined 78.6% (from 1999 to 2018). In previous research, larval infection rates averaged at least twice the infection rates of adults, because all infections originate in the larval stage, and at least 75% of infected larvae die before pupation. This means that an adult infection rate of 29.5%, combined with previously observed 50% reductions in egg production by infected females, are consistent with the observed population declines. The current distribution of O. popilliae in southern Michigan was determined by sampling Japanese beetle larvae and adults at 38 sites in 2017 and 2018. Ovavesicula popilliae was found at 21 of 38 sites and in 16 of 21 counties, compared with two sites in one of 16 counties when it was first detected in Michigan in 1999 and 2000.

Repeated exposure of fluazinam fungicides affects gene expression profiles yet carries no costs on a nontarget pest

Fungicides are used to control pathogenic fungi of crop species, but they have also been shown to alter behavioral, life history and fitness related traits of nontarget insects. Here, we tested the fungicide effects on feeding behavior, survival and physiology of the nontarget pest insect, the Colorado potato beetle (CPB) (Leptinotarsa decemlineata). Feeding behavior was studied by a choice test of adult beetles, which were allowed to choose between a control and a fungicide (fluazinam) treated potato leaf. Larval survival was recorded after 24 and 72 h exposure to control and fungicide-treated leaves with 2 different concentrations. The adults did not show fungicide avoidance behavior. Similarly, survival of the larvae was not affected by the exposure to fungicides. Finally, to understand the effects of fungicides at the physiological level (gene expression), we tested whether the larval exposure to fungicide alter the expression of 5 metabolic pathway and stress associated genes. Highest concentration and 72-h exposure caused upregulation of 1 cytochrome P450 (CYP9Z14v2) and 1 insecticide resistance gene (Ldace1), whereas metabolic detoxification gene (Ugt1) was downregulated. At 24-h exposure, highest concentration caused downregulation of another common detoxification gene (Gs), while both exposure times to lowest concentration caused upregulation of the Hsp70 stress tolerance gene. Despite these overall effects, there was a considerable amount of variation among different families in the gene expression levels. Even though the behavioral effects of the fungicide treatments were minor, the expression level differences of the studied genes indicate changes on the metabolic detoxifications and stress-related pathways.

Adult Popillia japonica as an Otorhinolaryngologic Invasive Foreign Body in a Rural Area

Otorhinolaryngologic foreign bodies may be encountered in-office visits, the emergency department, and speciality consultations. These include food, toys, and other small items, are present in pediatric patients. Because patients may be asymptomatic and the insertion of the foreign body not observed, obtaining medical care may be delayed. Conversely, insects as foreign bodies, especially in the external ear canal, can cause a patient significant pain and distress, directing the patient to seek immediate care. Here, we present a case of an adult Japanese beetle (Popillia japonica) as a foreign body in the ear of a 14-year-old female. A review of otorhinolaryngologic foreign bodies is also discussed, with particular attention to the ear and rural location. This case highlights the potential for agricultural insects to act as invasive foreign bodies, especially in areas where they are known to be endemic pests and the consequences of delayed treatment.

Agricultural fungicides inadvertently influence the fitness of Colorado potato beetles, Leptinotarsa decemlineata, and their susceptibility to insecticides

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is an agricultural pest of solanaceous crops which has developed insecticide resistance at an alarming rate. Up to this point, little consideration has been given to unintended, or inadvertent effects that non-insecticide xenobiotics may have on insecticide susceptibility in L. decemlineata. Fungicides, such as chlorothalonil and boscalid, are often used to control fungal pathogens in potato fields and are applied at regular intervals when L. decemlineata populations are present in the crop. In order to determine whether fungicide use may be associated with elevated levels of insecticide resistance in L. decemlineata, we examined phenotypic responses in L. decemlineata to the fungicides chlorothalonil and boscalid. Using enzymatic and transcript abundance investigations, we also examined modes of molecular detoxification in response to both insecticide (imidacloprid) and fungicide (boscalid and chlorothalonil) application to more specifically determine if fungicides and insecticides induce similar metabolic detoxification mechanisms. Both chlorothalonil and boscalid exposure induced a phenotypic, enzymatic and transcript response in L. decemlineata which correlates with known mechanisms of insecticide resistance.

Sublethal effects of the novel cis-nitromethylene neonicotinoid cycloxaprid on the cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae)

Cycloxaprid is a novel cis-configuration neonicotinoid insecticide that is effective against a wide range of insect pests, including those that are resistant to conventional neonicotinoids. In this study, life table parameters were applied to estimate the cycloxaprid-induced sublethal effects on Aphis gossypii. The results indicated that the LC₂₀ (0.81 mg a.i. L⁻¹) of cycloxaprid significantly decreased the pre-oviposition period in first-progeny adults. Additionally, the life expectancy of F1 generation adults was reduced. However, no significant differences were observed for the intrinsic rate of increase (r_i), finite rate of increase (λ), net reproductive rate (R₀), or mean generation time (T) of F1 individuals. Therefore, resurgence in the A. gossypii population induced by a low concentration of cycloxaprid might not occur. Additionally, the response of the detoxification enzymes showed that cycloxaprid at the LC₂₀ inhibited cytochrome P450 monooxygenase (P450) and glutathione S-transferase (GST) activities at 6 h after exposure. Such inhibition of P450 and GST activities could lead to a decrease in the metabolism of cycloxaprid, which would increase the efficacy of cycloxaprid. Therefore, our results contribute to the assessment of the overall effects of cycloxaprid on A. gossypii.

Imidacloprid seed treatments affect individual ant behavior and community structure but not egg predation, pest abundance or soybean yield

BACKGROUND

Neonicotinoid seed treatments are under scrutiny because of their variable efficacy against crop pests and for their potential negative impacts on non-target organisms. Ants provide important biocontrol services in agroecosystems and can be indicators of ecosystem health. This study tested for effects of exposure to imidacloprid plus fungicide or fungicide-treated seeds on individual ant survival, locomotion and foraging capabilities and on field ant community structure, pest abundance, ant predation and yield.

RESULTS

Cohorts of ants exposed to either type of treated seed had impaired locomotion and a higher incidence of morbidity and mortality but no loss of foraging capacity. In the field, we saw no difference in ant species richness, regardless of seed treatment. Blocks with imidacloprid did have higher species evenness and diversity, probably owing to variable effects of the insecticide on different ant species, particularly Tetramorium caespitum. Ant predation on sentinel eggs, pest abundance and soybean growth and yield were similar in the two treatments.

CONCLUSION

Both seed treatments had lethal and sublethal effects on ant individuals, and the influence of imidacloprid seed coating in the field was manifested in altered ant community composition. Those effects, however, were not strong enough to affect egg predation, pest abundance or soybean yield in field blocks. © 2016 Society of Chemical Industry.