Histopathological Evaluation of Tissue Specific Responses of Subacute Clothianidin Administration in Oncorhynchus mykiss

Clothianidin, one of the latest members of neonicotinoids, is a systemic insecticide of the neonicotinoid group that affects the central nervous system by acting as a nicotinic acetylcholine receptor agonist. Although it is stated that it has no dangerous potential for aquatic organisms, accumulation in water basins is important in terms of environmental toxicity. In this study, the histopathological changes caused by clothianidin applied in subacute application (7 days) form and in environmental doses (3, 15 and 30 µg/L) in the brain, kidney, muscle and gill tissue of juvenile Oncorhynchus mykiss were determined. Parallel to the administration of increasing doses of clothianidin, an increase in the severity of pathological lesions is observed in the brain, muscle, kidney and gill tissue. In particular, it shows that as a result of the accumulation of pesticides in aquatic organisms, lesions may develop as tissue-specific responses, thus leading to tissue dysfunction.

Response of Late Sown Pigeonpea (Cajanus cajan (L.) Mill Sp.) to Nutrient and Pest Management

A field experiment was conducted at Oilseed Research Farm, C.S.A. University of agriculture and Technology, Kanpur (Uttar Pradesh) continuously three years since 2016-17 to 2018-19 to study the response of late sown pigeonpea (Cajanus cajan L. Millsp.) to nutrient and pest management. The experiment was laid out in a Randomized Complete Block Design in three replications. Among the all treatments, recommended dose of fertilizer (N:P:K:S:Zn kg ha-1:: 20:50:20:20:20) application was common. Investigation results revealed that the application of T6 (RDF + 2% urea + 0.5% B + 0.5% Zn spray at 50% flowering) + Indoxacarb at flowering + one systemic insecticide 15 days after first spray was produces 30.89% higher grain yield and Gross income; and 28.27% higher B:C cost ratio over the application of RDF. Therefore, in comparison to RDF, particularly on economic point of view, we may conclude that the application of RDF + 2% urea + 0.5% B + 0.5% Zn spray at 50% flowering + Indoxacarb 14.5% SC at flowering + one systemic insecticide 15 days after first spray may be suggested for nutrient and pest management practice in long duration pigeonpea to attained the maximum grain yield and economic return.

Chemical Control of Corythucha arcuata (Say, 1832), an Invasive Alien Species, in Oak Forests

In addition to the classic biotic and abiotic factors that have disrupted the health of forests throughout history, lately, the balance of forest ecosystems has been disturbed by different phenomena such as climate change, pollution, and, especially, biological invasions of invasive alien species. One of the alien species that has invaded Europe relatively quickly is an insect species of North American origin, the oak lace bug (Corythucha arcuata Say, 1832 Heteroptera: Tingidae). In the context of the rapid spread of infestations and the severity of attacks on oak trees in infested forests, this paper aims to assess measures to manage this species in the future. Namely, the effect of aerial chemical treatments on oak lace bug has been investigated with two influencing factors: the mode of insecticide action (contact and systemic) and the treatment volume (low volume and ultra-low volume). The experiment was conducted in two forests over a total area of 350 hectares. The results show that the reduction of the nymph population varied from 91% to 96%. However, the residual population was sufficient to allow differentiated re-infestations over time, more quickly after contact insecticide sprays (22 days after treatment) and slowly after systemic insecticide sprays (more than a month after treatment). This re-infestation time difference had implications on attack intensity as well, with stronger leaf discoloration observed in areas treated with a contact insecticide compared with those treated with a systemic insecticide.

Risk Assessment of Flonicamid Resistance in Musca domestica (Diptera: Muscidae): Resistance Monitoring, Inheritance, and Cross-Resistance Potential

Flonicamid is a chordotonal modulator and novel systemic insecticide that has been used frequently for controlling a broad range of insect pests. The risk of flonicamid resistance was assessed through laboratory selection and determining inheritance pattern and cross-resistance potential to five insecticides in house fly, Musca domestica L. Very low to high flonicamid resistance in M. domestica populations was found compared with the susceptible strain (SS). A flonicamid-selected (Flonica-RS) M. domestica strain developed 57.73-fold resistance to flonicamid screened for 20 generations compared with the SS. Overlapping 95% fiducial limits of LC50 of the F1 and F1ǂ, and dominance values (0.87 for F1 and 0.92 for F1ǂ) revealed an autosomal and incomplete dominant flonicamid resistance. The monogenic model of resistance inheritance suggested a polygenic flonicamid resistance. The Flonica-RS strain displayed negative cross-resistance between flonicamid and sulfoxaflor (0.10-fold) or clothianidin (0.50-fold), and very low cross-resistance between flonicamid and flubendiamide (4.71-fold), spinetoram (4.68-fold), or thiamethoxam (2.02-fold) in comparison with the field population. The estimated realized heritability (h2) value of flonicamid resistance was 0.02. With selection mortality 40–90%, the generations required for a 10-fold increase in LC50 of flonicamid were 94–258 at h2 (0.02) and slope (3.29). Flonicamid resistance was inherited as autosomal, incomplete dominant, and polygenic in the Flonica-RS. Negative or very low cross-resistance between flonicamid and sulfoxaflor, clothianidin, flubendiamide, spinetoram, and thiamethoxam means that these insecticides can be used as alternatives for controlling M. domestica. These data can be useful in devising the management for M. domestica.

Limited Scope Risk Assessment for Nontarget Ground-Dwelling Arthropods From Systemic Insecticide Applications to Young Pines

The Nantucket pine tip moth (NPTM) [Rhyacionia frustrana (Comstock)], a native regeneration pest on young loblolly pines (Pinus taeda L.), negatively impacts pine growth. An emerging management approach is to apply systemic insecticides to seedlings to reduce NPTM damage. These systemic insecticide applications generally occur once, perhaps twice, during the first few years of loblolly pine growth. However, these applications could lead to unintended environmental consequences to nontarget organisms. The purpose of this study was to assess potential nontarget effects from four systemic insecticide applications by assessing ground-dwelling arthropod trap catch, with a focus on collembolan trap catch and genera richness. Loblolly seedlings (24 seedlings per plot) at three sites in southeast Georgia were treated with either chlorantraniliprole, dinotefuran, fipronil, or imidacloprid or left untreated as a control. Arthropods were collected with pitfall traps that were deployed for 5 d in July, August, and September 2019, 7–9 mo after treatment. Ground-dwelling arthropod trap catch, arthropod order trap catch, collembolan trap catch, and collembolan genera richness did not vary among insecticide treatments and the untreated control in this mid-term insecticide risk assessment. While no significant effects of insecticide treatment were observed, ground-dwelling arthropod trap catch, collembolan trap catch, and collembolan genera richness differed among collection times. This study was the first of its kind in a young pine stand setting and is an important first step to understanding risk in these settings. Information on nontarget risks of management practices informs growers of the level of environmental risk associated with systemic insecticides.

Imidacloprid Movement into Fungal Conidia Is Lethal to Mycophagous Beetles

Applications of systemic pesticides can have unexpected direct and indirect effects on nontarget organisms, producing ecosystem-level impacts. We investigated whether a systemic insecticide (imidacloprid) could be absorbed by a plant pathogenic fungus infecting treated plants and whether the absorbed levels were high enough to have detrimental effects on the survival of a mycophagous beetle. Beetle larvae fed on these fungi were used to assess the survival effects of powdery mildew and imidacloprid in a factorial design. Fungal conidia were collected from treated and untreated plants and were tested for the presence and concentration of imidacloprid. The survival of beetles fed powdery mildew from imidacloprid-treated leaves was significantly lower than that of the beetles from all other treatments. Imidacloprid accumulated in fungal conidia and hyphae was detected at levels considered lethal to other insects, including coccinellid beetles. Water-soluble systemic insecticides may disrupt mycophagous insects as well as other nontarget organisms, with significant implications for biodiversity and ecosystem function.

Imidacloprid Movement into Fungal Conidia is Lethal to Mycophagous Beetles

Applications of systemic pesticides can have unexpected direct and indirect effects on nontarget organisms, producing ecosystem-level impacts.We investigated whether a systemic insecticide (imidacloprid) could be absorbed by a plant pathogenic fungus infecting treated plants and whether the absorbed levels were high enough to have detrimental effects on the survival of a mycophagous beetle. Beetle larvae fed on these fungi were used to assess the survival effects of powdery mildew and imidacloprid in a factorial design. Fungal conidia were collected from treated and untreated plants and were tested for the presence and concentration of imidacloprid.Survival of beetles fed powdery mildew from imidacloprid-treated leaves was significantly lower than that of beetles from all other treatments.Imidacloprid accumulated in fungal conidia and hyphae was detected at levels considered lethal to other insects, including coccinellid beetles.Water-soluble systemic insecticides may disrupt mycophagous insects as well as other nontarget organisms, with significant implications for biodiversity and ecosystem function.

Optimising systemic insecticide use to improve malaria control

BackgroundLong-lasting insecticidal nets and indoor residual sprays have significantly reduced the burden of malaria. However, several hurdles remain before elimination can be achieved: mosquito vectors have developed resistance to public health insecticides, including pyrethroids, and have altered their biting behaviour to avoid these indoor control tools. Systemic insecticides, drugs applied directly to blood hosts to kill mosquitoes that take a blood meal, offer a promising vector control option. To date, most studies focus on repurposing ivermectin, a drug used extensively to treat river blindness. There is concern that overdependence on a single drug will inevitably repeat past experiences with the rapid spread of pyrethroid resistance in malaria vectors. Diversifying the arsenal of systemic insecticides used for mass drug administration would improve this strategy’s sustainability.MethodsHere, a review was conducted to identify systemic insecticide candidates and consolidate their pharmacokinetic/pharmacodynamic properties. The impact of alternative integrated vector control options and different dosing regimens on malaria transmission reduction are illustrated through mathematical model simulation.ResultsThe review identified drugs from four classes commonly used in livestock and companion animals: avermectins, milbemycins, isoxazolines and spinosyns. Simulations predicted that isoxazolines and spinosyns are promising candidates for mass drug administration, as they were predicted to need less frequent application than avermectins and milbemycins to maintain mosquitocidal blood concentrations.ConclusionsThese findings will provide a guide for investigating and applying different systemic insecticides to achieve more effective and sustainable control of malaria transmission.