ABSTRACT
Essential oils from plants have remarkable biological properties, for example as insecticides and acaricides. Here we provide chemical analysis and evaluate the toxicity of the essential oil of Mentha piperita (Lamiaceae) and its main constituent menthol against Tetranychus urticae Kogan 1836 (Acari: Tetranychidae), a polyphagous pest present in agricultural landscapes. The essential oil was obtained from M. piperita leaves via hydrodistillation. Subsequently, concentration-response bioassays in adult females (fumigation and contact) were conducted to evaluate the lethal effect on the mite with three exposure intervals. We also evaluated the reproductive performance of females after exposure. Both substances were lethal in the fumigation bioassay, in addition, the essential oil was about 6-fold more toxic than menthol after 24 and 48 h of exposure. The fecundity of T. urticae females decreased inversely proportional to the increase of the used concentrations. Essential oil contact tests showed sublethal effects, with low mortality and reproductive stimulation of T. urticae females. Therefore, menthol and M. piperita essential oil can be considered potential acaricides for T. urticae by fumigant exposure due to the deleterious effect in adults and reduction in the number of individuals in subsequent generations, that represents a promising management tool.
Subject(s)
Lamiaceae , Oils, Volatile , Tetranychidae , Humans , Animals , Mentha piperita , Monoterpenes , Menthol/pharmacology , Oils, Volatile/toxicityABSTRACT
Insect viruses have been used to protect crops and forests worldwide for decades. Among insect viruses, isolates of Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) have proven potential for the control of Spodoptera frugiperda (J. E. Smith) (FAW) (Lepidoptera: Noctuidae), a pest of many economically essential crops across several continents. Mass production of SfMNPV depends on an in vivo system using host insect rearing. However, many factors can limit its production, including abiotic factors and host characteristics, such as the stage of development and an antagonist intraspecific interaction. Thus, to improve in vivo production, we verified the most suitable larval age to inoculate the virus and the influence of incubation temperature on viral production. Subsequently, cannibal behavior was verified in FAW larvae reared at different densities, while reproducing the conditions of the best treatments. The highest viral yield occurred when FAW larvae were inoculated at 10 and 8 days old and incubated at 22 °C and 25 °C, respectively. Nonetheless, survival (lethal period in days) and cannibal behavior were positively influenced by larval development, which potentially increases the load of contamination and requires larval individualization for these production conditions. In contrast, 4-day-old larvae, which were inoculated and incubated at 31 °C, also demonstrated high viral production, with lower rates of cannibalism and death on the same day, thereby showing potential. The information presented in this study is useful for the optimization of the in vivo production systems of SfMNPV.
Subject(s)
Nucleopolyhedroviruses , Animals , Crops, Agricultural , Larva , Spodoptera , Zea maysABSTRACT
Phytovirus vectors Frankliniella schultzei (Trybom, 1920) (Thysanoptera: Thripidae) and Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae) feed on crops of great economic importance brings large economic losses worldwide to cultivated species such as tomato and cotton. F. schultzei transmits Tospovirus, Groundnut ring spot virus (GRSV) and Tomato spotted wilt virus (TSWV) to tomato plants and M. persicae transmits Potato virus Y (PVY), Tomato yellow top virus (ToYTV) and Tomato bottom yellow leaf virus (TBYLV) to tomato crops. Chemical constituents of essential oils have been increasingly studied because they present a wide range of biological activities. The aim of this work was to characterize Cymbopogon citratus essential oil and evaluate its potential insecticide activity against F. schultzei and M. persicae. The essential oil was obtained from fresh leaves by hydrodistillation using a Clevenger apparatus. Its yield (1.04%) was determined relative to the dry mass of the plant. Qualitative analysis was performed by gas chromatography coupled to mass spectrometry and chemical constituent content was determined by gas chromatography with a flame ionization detector. Nine compounds were identified, with geranial (49.98%) and neral (37.78%) being the major components. The insects were sprayed with C. citratus essential oil at different concentrations using a Potter tower. The LC50 values for M. persicae and F. schultzei were 0.28% and 1.49%, respectively. Essential oil from C. citratus is a promising natural alternative for developing pesticides to manage M. persicae.
Os vetores de fitovírus Frankliniella schultzei (Trybom, 1920) (Thysanoptera: Thripidae) e Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae) se alimentam de culturas de grande importância econômica, trazendo grandes perdas econômicas em todo o mundo para as espécies cultivadas, como tomate e algodão. F. schultzei transmite Tospovirus, Groundnut ring spot virus (GRSV) e Tomato spotted wilt virus (TSWV) em tomateiro and M. persicae transmite Potato virus Y (PVY), Tomato yellow top virus (ToYTV) e Tomato bottom yellow leaf virus (TBYLV) ao tomateiro. Os constituintes químicos dos óleos essenciais têm sido cada vez mais estudados, pois apresentam uma ampla gama de atividades biológicas. O objetivo deste trabalho foi caracterizar o óleo essencial de Cymbopogon citratus e avaliar o seu potencial inseticida sobre F. schultzei e M. persicae. O óleo essencial foi obtido a partir de folhas frescas por hidrodestilação utilizando um aparelho Clevenger. O seu rendimento (1,04%) foi determinado em relação à massa seca da planta. A análise qualitativa foi realizada por cromatografia gasosa acoplada a espectrometria de massa e o teor dos constituintes químicos foi determinado por cromatografia gasosa com detector de ionização de chama. Nove compostos foram identificados, com geranial (49,98%) e neral (37,78%), sendo os componentes principais. Os insetos foram pulverizados com óleo essencial de C. citratus em diferentes concentrações utilizando uma torre de Potter. Os valores de CL50 de M. persicae e F. schultzei foram de 0,28% e 1,49%, respectivamente. Óleo essencial de C. citratus é uma alternativa natural promissor para o desenvolvimento de inseticidas para o manejo de M. persicae.
