Douglas Rafael e Silva Barbosa

Lethal and sublethal responses of Sitophilus zeamais populations to essential oils

The present study aimed to assess the lethal and sublethal responses of five populations of S. zeamais to the essential oils of Ocimum basilicum and Piper hispidinervum, through toxicity, locomotor behavior (flight and walking activities) and physiological (respiration rate and body mass) evaluations. The populations of S. zeamais were obtained from Machado—MG, Paracatu—MG, Piracicaba—SP, Recife—PE and Tunápolis—SC. To estimate the LC50 of each oil for each population, fumigation tests were performed. The population from Recife exhibited the lowest instantaneous rate of increase (ri) as well the lowest consumption of grain mass. However, Piracicaba was considered the susceptibility pattern, presenting the lowest LC50 for both essential oils, no statistical difference was observed among populations or treatments in the flight activity bioassays. The essential oils effect on walking activity and respiration rates varied among populations. The population from Recife presented the highest walked distance and walk speed, with the lowest resting time and number of stops, as well as the lowest respiration rate and body mass. The present study highlights the importance of the study on population responses, as the five populations of S. zeamais exhibited different patterns of toxic and behavioral effects when subjected to the essential oils of P. hispidinervum and O. basilicum.

Sublethal Effects of Essential Oils From Eucalyptus staigeriana (Myrtales: Myrtaceae), Ocimum gratissimum (Lamiales: Laminaceae), and Foeniculum vulgare (Apiales: Apiaceae) on the Biology of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract Spodoptera frugiperda (Smith 1797) (Lepidoptera: Noctuidae) is a major pest of maize, Zea mays L. Its control is often achieved through repeated applications per season of insecticides, which may lead to adverse effects on the ecosystem. Thus, the study of alternative methods with less environmental impact has expanded to include the use of essential oils. These oils are products of the secondary metabolism in plants, and their insecticidal activity has been widely demonstrated in populations of many pest insects. This study evaluated the insecticidal activities of essential oils from Eucalyptus staigeriana, Ocimum gratissimum, and Foeniculum vulgare on Spodoptera frugiperda. Gas chromatography–mass spectrometry profiles and contact toxicity of these oils as well as their sublethal effects on larvae and reproductive parameters in adults were evaluated. All three oils had sublethal effects on S. frugiperda; however, the oil of O. gratissimum showed the best results at all doses tested. These essential oils may have promise for control of S. frugiperda.

Microwave radiation to control Callosobruchus maculatus (Coleoptera: Chrysomelidae) larvae in cowpea cultivars

Disinfestation of stored grains using microwave is an alternative to chemical fumigants for controlling the cowpea weevil Callosobruchus maculatus (Fabricius) (Bruchinae). Cowpea grains (BRS Paraguaçu and BRS Xique xique cv.) infested with larvae were exposed to 240 W microwave power level for 0 (control) 30, 60, 90, 120 and 150 s. For both cultivars, there was a reduction on the number of insects emerged per grain, number of insects emerged per treatment and an increase on the egg–adult period with increase of the exposure period. The microwave exposure periods lethal to C. maculatus larvae were 120 and 150 s.

Bioatividade dos extratos aquosos de folhas de pimenta malagueta e eucalipto sobre Zabrotes subfasciatus em grãos de fava

Os extratos vegetais atualmente representam uma alternativa importante no controle de insetos-praga. Objetivou-se com este trabalho analisar os efeitos de extratos aquosos de folhas de pimenta malagueta ( Capsicum frutescens ) e eucalipto ( Eucalyptus sp.) sobre Zabrotes subfasciatus em fava. Foram realizados dois bioensaios no laboratorio de Entomologia, Departamento de Biologia, Centro de Ciencias da Natureza da Universidade Federal do Piaui, em delineamento experimental inteiramente casualizado, totalizando cinco tratamentos [0% (testemunha), 30%, 60%, 80% e 100 %], cada um com quatro repeticoes, onde os parâmetros, numero de insetos mortos, numero de ovos e emergencia de adultos foram avaliados. O extrato aquoso de folhas de pimenta malagueta nao foi eficiente contra o caruncho Z. subfasciatus , pois, houve mortalidade media de 20% dos insetos nas concentracoes de 80 e 100%, e com o aumento da concentracao teve-se um estimulo a oviposicao e emergencia destes. O extrato aquoso de folhas de Eucalyptus sp. foi eficiente sobre a mortalidade, oviposicao e emergencia de Z. subfasciatus , com o aumento da concentracao observou-se maior mortalidade, atingindo 40% dos individuos; reducao da oviposicao, 13% em relacao a testemunha e as demais concentracoes, e emergencia dos besouros. Bioactivity of the aqueous extracts of chilli pepper and eucalyptus leaves on Zabrotes subfasciatus in fava beans Abstract: The plant extracts currently represent an important alternative in the control of insect pests. The objective of this paper was to analyze the effects of aqueous extracts of leaves of chilli pepper ( Capsicum frutescens ) and eucalyptus ( Eucalyptus sp.) on Zabrotes subfasciatus in fava. Two bioassays were performed in the entomology laboratory, Department of Biology, Nature Sciences Center of the Federal University of Piaui, in a completely randomized experimental design, totaling five treatments [(0% (control), 30%, 60%, 80% and 100%], each one with four replicates, where the parameters, number of dead insects, number of eggs and emergence of adults were evaluated. The aqueous extract of leaves of chilli pepper was not efficient against the weevil Z. subfasciatus , because, there was an average mortality of 20% of the insects in the concentrations of 80 and 100%, and with the increase of the concentration there was a stimulus to oviposition and emergence. The aqueous extract of leaves of Eucalyptus sp. was efficient on the mortality, oviposition and emergence of Z. subfasciatus , with the increase in concentration, a higher mortality was observed, reaching 40% of the individuals; reduction of oviposition, 13% in relation to control and other concentrations, and emergence of beetles.

Lethal and sublethal effects of pesticides in the management of Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) on Capsicum annuum L.

BACKGROUND The evaluation of lethal and sublethal effects is of great importance for a complete assessment of the total impact of chemical compounds upon pest populations and the development of management strategies. In this study, we evaluated the lethal and sublethal effects of different synthetic and botanical products on the broad mite Polyphagotarsonemus latus (Banks), a major pest of Capsicum annuum L. and other crops. RESULTS Abamectin had the highest lethal effect on P. latus, followed by spiromesifen, azadirachtin, neem oil and nitrogen fertiliser + citric acid. The sublethal effects of the products were indicated by the influence on mite population growth, affecting the numbers of females, males, larvae, pupae and eggs. Furthermore, a negative instantaneous rate of increase in P. latus and repellent effects were observed. CONCLUSION The lethal and sublethal effects of abamectin, spiromesifen, azadirachtin and neem oil significantly affect P. latus population growth, as well as causing repellence to this mite on C. annuum, and they should be considered in the integrated pest management of this mite.

Fumigação e repelência de óleos essenciais sobre Callosobruchus maculatus (Coleoptera: Chrysomelidae: Bruchinae) em feijão-caupi

The objective of this work was to assess the fumigant and repellent effects of essential oils on adults of Callosobruchus maculatus and to identify the chemical composition of two of the tested essential oils. For the fumigation test, the oils of Schinus terebinthifolius, Piper aduncum, Syzygium aromaticum, Piper hispidinervum, Cymbopogon citratus, Cinnamomum zeylanicum, and the eugenol compound were tested at different concentrations on C. maculatus adults. For the repellency test, the oils of S. terebinthifolius, P. aduncum, P. hispidinervum, S. aromaticum, Jatropha curcas, and Ricinus communis were evaluated. In the fumigation test, it was observed that P. aduncum and eugenol showed the highest and lowest LC50s, of 169.50 and 0.28 μL L-1 air, respectively. In the repellency test, the oils of S. aromaticum and P. hispidinervum were repellent to C. maculatus. Gas chromatography coupled to mass spectrometry (GC-MS) analysis of these two oils identified 42 compounds, of which safrole was the main component of P. hispidinervum and eugenol of S. aromaticum. The essential oils of S. aromaticum, C. zeylanicum, and the eugenol compound are the most promising to control C. maculatus, via fumigation.

Resistência de genótipos de feijão-caupi ao ataque de Callosobruchus maculatus (Fabr., 1775) (Coleoptera: Chrysomelidae: Bruchinae)

The objective of this study was to evaluate the resistance of 4 genotypes of cowpea (Vigna unguiculata) to the bean weevil Callosobruchus maculatus (Fabr., 1775). The genotypes evaluated were BR 17-Gurgueia, BRS Rouxinol, TE96-290-12G and BRS Guariba. Tests were conducted with and without possibility of choice, in a completely randomized design, totaling 4 treatments each with 5 replicates, evaluating the number of eggs, number of emerged insects, egg viability (%) and instantaneous rate of population growth. In the test with possibility of choice the genotype TE96-290-12G was revealed as the most resistant. BRS Rouxinol was the most susceptible genotype.

Radiação microondas para o controle de pupas de Callosobruchus maculatus em cultivares de feijão-caupi - DOI:10.5039/agraria.v6i4a845

Objetivou-se neste trabalho investigar os efeitos da radiacao microondas em pupas de Callosobruchus maculatus (Fabr., 1775) nas cultivares de feijao-caupi ( Vigna unguiculata ) BRS Paraguacu e BRS Xique-xique. Para a radiacao, utilizou-se um forno microondas comercial, com frequencia de 2.450 MHz, rendimento de potencia de 800 W, em baixa potencia (30%), sendo os tempos de exposicao a radiacao microondas 0, 60, 90, 120 e 150 segundos. Observou-se, para ambas as cultivares, reducao no numero de insetos emergidos por grao, numero de insetos emergidos por tratamento e aumento do periodo ovo-adulto, com exposicao a 60 segundos de radiacao. Os tempos de 90, 120 e 150 segundos de exposicao a radiacao microondas foram letais para 100% das pupas de C. maculatus .