Evaluation of Piper marginatum (Piperales: Piperaceae) Oil and Geraniol on the Embryonic Development of Spodoptera frugiperda (Lepidoptera: Noctuidae) in Comparison to Formulated Products.

Essential oils and their isolated constituents are constantly being studied for the control of insect pests. In this context, the present research reports the chemical composition of Piper marginatum (Jacq.) oil aiming to: 1) establish lethal concentrations LC30 and LC50 for this oil and the compound geraniol, 2) histologically examine the embryonic development of Spodoptera frugiperda (J.E. Smith) through light microscopy and scanning electron microscopy (SEM), as well as 3) compare the efficacy of the P. marginatum oil with that of the botanical insecticide azadirachtin, the synthetic insecticide deltamethrin, and acetone as a negative control. Semithin sections of S. frugiperda eggs revealed that the oil, geraniol, azadirachtin, and deltamethrin affected embryonic development at both concentrations. However, geraniol and the oil were more efficient because they caused more significant damage, even at lower concentrations. SEM revealed that all products altered the morphology of the eggs, modifying the structure of the chorion and making the eggs nonviable. Thus, this work demonstrates that P. marginatum oil is effective in the control of S. frugiperda because it results in embryonic damage even at the lowest concentrations.

Microscopic analysis of Spodoptera frugiperda (Lepidoptera: Noctuidae) embryonic development before and after treatment with azadirachtin, lufenuron, and deltamethrin.

The botanical insecticides, growth regulators, and pyrethroids have an effect on the biology of Spodoptera frugiperda (Smith). However, no emphasis has been given to the effect of these insecticides on embryonic development of insects, in histological level. Thus, this research aimed to examine by light and scanning electron microscopy S. frugiperda eggs and to describe the embryonic development, before and after immersion treatment, using commercial concentrations and lower concentrations than commercial ones, of the compounds lufenuron (Match), azadirachtin (AzaMax), and deltamethrin (Decis-positive control). For light microscopy semithin sections of eggs were used, and for scanning electron microscopy, images of the surface of eggs, treated and untreated with insecticides. The morphological characteristics of S. frugiperda eggs, in general, were similar to those described in the literature for most of the insects in the order Lepidoptera. Spherical eggs slightly flattened at the poles, with chorion, yolk, vitelline membrane, and embryo formation. In both microscopic analysis, we observed that insecticides acted immediately and independent of concentration, resulting absence, or incomplete embryo, presented yolk granules widely dispersed, without vitellophage formation, chorion disintegration, disorganized blastoderm, presenting vacuoles, yolk region with amorphous cells, and formation of completely uncharacterized appendages. Thus, we conclude that the compounds lufenuron and azadirachtin interfere on S. frugiperda embryonic development.

[Morphology of the alimentary canal of Spodoptera frugiperda (J E Smith) larvae (Lepidoptera: Noctuidae) fed on neem-treated leaves]. / Morfologia do canal alimentar de lagartas de Spodoptera frugiperda (J E Smith) (Lepidoptera: Noctuidae) alimentadas com folhas tratadas com nim.

Research involving plants with insecticide activity evolved significantly in the last decades. Among these plants, the neem tree, Azadirachta indica, is commonly used against several insects, mainly Lepidoptera. The neem efficiency depends on the target insect and on the concentration used. A barrier against potential toxic agents ingested together with the food is the alimentary canal. Thus, this research aimed to describe the histology of the alimentary canal of Spodoptera frugiperda (J E Smith) larvae fed on leaves treated with neem (Neemseto) at a concentration of 0.5% and 1.0% and non treated, at different intervals (48, 96, 144, 192 and 240 h), by quantifying the regenerative cells and analyzing the secretion of the mesenteron histochemically. Larvae were immobilized at low temperatures (-4 degrees C), the alimentary canal was removed, fixed in Boüin s aqueous, embedded in paraplast and historesin, sectioned and stained with hematoxilin-eosin and periodic acid- Schiff. The histology of the alimentary canal of S. frugiperda was similar to other lepidopterans. Neem effects on morphology were seen only in the mesenteron, depending on the time and concentration used, such as: epithelium, reduction on regenerative cells and on the secretory activity in this region, confirmed by the histochemistry in both neem concentrations. These alterations were observed after 96 h at 1.0%, and 144 h at 0.5%. These results indicate that neem (Neemseto), at the concentrations studied, may be effective to control S. frugiperda because it promotes meaningful morphological alterations in the mesenteron.

Morfologia do canal alimentar de lagartas de Spodoptera frugiperda (J E Smith) (Lepidoptera: Noctuidae) alimentadas com folhas tratadas com nim / Morphology of the alimentary canal of Spodoptera frugiperda (J E Smith) Larvae (Lepidoptera: Noctuidae) fed on neem-treated leaves

Pesquisas envolvendo plantas com atividade inseticida evoluíram bastante nas últimas décadas. Entre essas plantas destaca-se o nim, Azadirachta indica, que atua sobre várias espécies de insetos, principalmente Lepidoptera. Sua ação depende da espécie de inseto e concentração aplicada. Uma barreira contra potenciais agentes tóxicos ingeridos com o alimento é o canal alimentar. Assim, a pesquisa teve por objetivo descrever, histologicamente, o canal alimentar de lagartas de Spodoptera frugiperda (J E Smith) alimentadas com folhas tratadas com nim (Neemseto®), nas concentrações 0,5 e 1,0 por cento, e com folhas não tratadas, nos intervalos de 48, 96, 144, 192 e 240h, quantificar as células regenerativas e analisar, histoquimicamente, o produto de secreção do mesêntero. As lagartas foram imobilizadas a baixa temperatura (-4ºC), o canal alimentar foi retirado, fixado em Boüin aquoso, incluído em paraplast e historesina, e os cortes corados por hematoxilina-eosina e ácido periódico de Schiff. Histologicamente, o canal alimentar de S. frugiperda mostrou-se semelhante ao de outros lepidópteros. Alterações morfológicas só foram evidenciadas no mesêntero, sendo a sua intensidade dependente do tempo e da concentração utilizada. Observou-se degeneração do epitélio e redução de células regenerativas e de atividade secretora dessa região, em ambas as concentrações de nim. Essas alterações foram observadas após 96h a 1,0 por cento e 144h a 0,5 por cento. Esses resultados demonstram que o nim (Neemseto®), nas concentrações estudadas, pode ser efetivo para o controle de S. frugiperda por promover alterações morfológicas no mesêntero.

Research involving plants with insecticide activity evolved significantly in the last decades. Among these plants, the neem tree, Azadirachta indica, is commonly used against several insects, mainly Lepidoptera. The neem efficiency depends on the target insect and on the concentration used. A barrier against potential toxic agents ingested together with the food is the alimentary canal. Thus, this research aimed to describe the histology of the alimentary canal of Spodoptera frugiperda (J E Smith) larvae fed on leaves treated with neem (Neemseto®) at a concentration of 0.5 percent and 1.0 percent and non treated, at different intervals (48, 96, 144, 192 and 240h), by quantifying the regenerative cells and analyzing the secretion of the mesenteron histochemically. Larvae were immobilized at low temperatures (-4ºC), the alimentary canal was removed, fixed in Boüin´s aqueous, embedded in paraplast and historesin, sectioned and stained with hematoxilin-eosin and periodic acid- Schiff. The histology of the alimentary canal of S. frugiperda was similar to other lepidopterans. Neem effects on morphology were seen only in the mesenteron, depending on the time and concentration used, such as: epithelium, reduction on regenerative cells and on the secretory activity in this region, confirmed by the histochemistry in both neem concentrations. These alterations were observed after 96h at 1.0 percent, and 144h at 0.5 percent. These results indicte that neem (Neemseto®), at the concentrations studied, may be effective to control S. frugiperda because it promotes meaningful morphological alterations in the mesenteron.