Deltamethrin-Mediated Effects on Locomotion, Respiration, Feeding, and Histological Changes in the Midgut of Spodoptera frugiperda Caterpillars

Abstract

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is the main pest of maize crops, and effective methods for pest management are needed. The insecticidal efficacy of deltamethrin was evaluated against S. frugiperda for toxicity, survival, locomotion, anti-feeding, and histological changes in the midgut. Concentration–mortality bioassays confirmed that deltamethrin (LC50 = 3.58 mg mL−1) is toxic to S. frugiperda caterpillars. The survival rate was 99.7% in caterpillars not exposed to deltamethrin, decreasing to 50.3% in caterpillars exposed to LC50, and 0.1% in caterpillars treated with LC90. Spodoptera frugiperda demonstrated reduced mobility on deltamethrin-treated surfaces. Deltamethrin promoted a low respiration rate of S. frugiperda for up to 3 h after insecticide exposure, displaying immobilization and inhibiting food consumption. Deltamethrin induces histological alterations (e.g., disorganization of the striated border, cytoplasm vacuolization, and cell fragmentation) in the midgut, damaging the digestive cells and peritrophic matrix, affecting digestion and nutrient absorption.

Effects of Insect Growth Regulators on Mortality, Survival, and Feeding of Euprosterna elaeasa (Lepidoptera: Limacodidae) Larvae

“…In contrast, moderate feeding inhibition after exposure to fenoxycarb and pyriproxyfen has been reported in Abraxas suspecta Warren (Geometridae) [42] and Spodoptera litoralis Boisduval (Noctuidae) [43], respectively. The findings obtained here of a reduction in food consumption by E. elaeasa larvae, in both lethal concentrations, indicates a possible poisoning per os, perhaps due to alterations in the midgut [21], affecting digestive enzymes secretion [44] and energy metabolism [45] with possible suppression of the detoxification response [43,46], as observed in other insects after oral insecticide exposure [47][48][49][50][51]. In summary, the reduction in food consumption caused by IGRs on treated E. elaeasa larvae suggests feeding inhibition impairing the digestive process.…”

Origanum vulgare Essential Oil against Tenebrio molitor (Coleoptera: Tenebrionidae): Composition, Insecticidal Activity, and Behavioral Response

“…A decrease respiration results in high fitness cost and energy demand can be utilized to other metabolic functions [56]. A similar response occurs in other coleopteran pests such as Demotispa neivai Bondar (Coleoptera: Chrysomelidae) exposed to neem essential oil [10], S. granarius exposed to cinnamon essential oil [26], and T. molitor exposed to garlic essential oil [27] decreasing the oxygen consumption and disrupting of oxidative phosphorylation in respiration [13,21,57]. The findings obtained here, demonstrate that the larvae, pupae, and adults of T. molitor have low respiration rate when exposed to OEO with possible energy reallocated to other physiological functions and fitness costs.…”

Evaluation of ultra-low volume treatments on Culex quinquefasciatus (Diptera: Culicidae) abundance and relative age by parity dissection

“…In order to help combat insecticide resistance, STPMAD implemented a ground ULV rotation in 2020 between insecticides containing resmethrin and deltamethrin. Field data from this trial, in combination with laboratory resistance data, indicate that deltamethrin is effective locally and is of use for mosquito abatement, despite growing concern over its nontarget repercussions (Giordano et al 2020, McGregor et al 2021, Vinha et al 2021, Kenko et al 2022). Considering the apparent failure of resmethrin to reduce mosquito abundance or age, STPMAD is reevaluating whether it should be replaced in rotation by an insecticide with a different mechanism of action (i.e., malathion), used selectively against mosquito species with different resistance profiles, tested at a higher application rate, or eliminated from use entirely.…”