Effect of Serjania lethalis ethanolic extract on weed control Efeito do extrato etanólico de Serjania lethalis no controle de plantas daninhas

The objective of this study was to evaluate the effect of the ethanolic extract of Serjania lethalis leaves and stems on the diaspore germination and seedling growth of wild poinsettia (Euphorbia heterophylla) and barnyardgrass (Echinochloa crus-galli). The crude ethanolic extract was prepared from 100 g of dry plant material dissolved in 500 ml of ethanol. The extracts were solubilized in a buffer solution containing dimethyl sulfoxide (DMSO) at concentrations of 10.0, 7.5, 5.0 and 2.5 mg mL-1. The effect of these extracts was compared with herbicide oxyfluorfen in bioassays. The ethanolic extracts of S. lethalis leaves and stems inhibited the germination and seedling growth of barnyardgrass and wild poinsettia in a concentration-dependent manner. The reduction in the root length of E. heterophylla seedlings might be attributed to the reduced elongation of metaxylem cells. The phytotoxicity of the extracts ranged according to the receptor species, and for some variables, the inhibitory effect was similar, and even superior, to that of the commercial herbicide. Thus, S. lethalis extracts might be a promising alternative for sustainable weed management.<br>O objetivo deste estudo foi avaliar o efeito do extrato etanólico de folhas e caules de Serjania lethalis sobre a germinação dos diásporos e crescimento de plântulas de amendoim-bravo (Euphorbia heterophylla) e capim-arroz (Echinochloa crus-galli). O extrato bruto etanólico foi preparado na proporção de 100 g de material vegetal seco para 500 mL de etanol. A partir deste, os extratos foram solubilizados em solução tampão e dimetil sulfóxido (DMSO) nas concentrações 10,0, 7,5, 5,0 e 2,5 mg mL-1. Nos bioensaios comparou-se o efeito desses extratos com o herbicida oxyfluorfen. Os extratos etanólicos de folhas e caules de S. lethalisexerceram atividade inibitória no processo de germinação e no crescimento das plântulas de capim-arroz e amendoim-bravo, com efeito dependente da concentração. Verificou-se que a redução do crescimento radicular das plântulas de amendoim-bravo pode estar relacionada com a diminuição no alongamento das células do metaxilema. A fitotoxicidade dos extratos variou de acordo com a espécie receptora, sendo que para algumas variáveis o efeito inibitório foi similar e até mesmo superior ao do herbicida comercial. Desta maneira, pode-se dizer que os extratos de S. lethalis podem ser uma alternativa promissora para o manejo sustentável de plantas daninhas

Antibiosis Levels Of Common Bean Genotypes Toward Zabrotes Subfasciatus (boheman) (coleoptera: Bruchidae) And Its Correlation With Flavonoids

Expression of the antibiosis-resistance category to weevils has been evaluated in several bean genotypes with very promising results. Among the several causes responsible for this resistance category the arcelin protein and trypsin inhibitors stand out. Other mechanisms may be associated with plant resistance to the attack of weevils; however, few studies seek to discover these possible causes. Thus, our research aimed at identifying bean genotypes resistant to Zabrotes subfasciatus, classify them into resistance levels, quantify the content of flavonoids, and correlate it with data obtained from the genotypes. An antibiosis test was performed with beans of 43 genotypes and 40 replications (bean grains) under a completely randomized design. The biological parameters recorded from Z. subfasciatus were the periods from egg to larvae, larvae to adult, egg to adult, longevity and life cycle, in addition to egg viability, adults emerged, susceptibility relative index, adult weight, sex ratio, and the dry mass consumed by larvae. The chemical profile of flavonoids from each genotype was assessed by means of LC-MS. Based on the results of the weevil biological parameters and dry mass consumed provided by univariate and multivariate statistical analyses, the bean genotypes were classified into four levels of resistance (antibiosis): highly resistant, moderately resistant, susceptible and highly susceptible. Among the evaluated flavonoids, we could identify isoquercitrin; however, it has no correlation with the expression of resistance. From the results obtained in this work, more studies will be conducted with the genotypes that stood out as resistant, evaluating other resistance categories and defense mechanisms of these materials against the attack of Z. subfasciatus and other pests, as well as studies of other important agronomic characteristics aiming at future commercialization of the bean genotypes. © 2016 Elsevier Ltd.67637

In vitro acaricidal activity of neem (Azadirachta indica) seed extracts with known azadirachtin concentrations against Rhipicephalus microplus

AbstractThe effect of four extracts from neem seeds (Azadirachta indica) containing 2000, 5000, 9000 and 10,000ppm of azadirachtin A (AZA), quantified by high-performance liquid chromatography (HPLC) and diluted to 1.25%; 2.5%; 5.0%; 10.0% and 12.8% was verified by in vitro tests with engorged females and larvae of the cattle tick Rhipicephalus microplus. The results from the bioassays with the engorged females showed that the main toxic effect of the extracts was reduction of the reproductive parameters, with a sharp drop in the number of eggs laid and the hatching rate, mainly when the extracts were diluted to 10.0% and 12.8%. The product effectiveness (PE) calculations for all the solutions tested showed that the AZA solution at 10,000ppm (N10) was the most effective. However, statistical analysis of the PE data obtained for the proportional AZA concentrations in the different diluted extracts showed significance (P<0.05) of the effects included in the model (extract dilution, principle effect (classificatory) of the assay (extract) and the interaction between the two), indicating significant variations due to the dilution, the test and the interaction between the two factors in the tests with engorged females. For solutions N2, N5, and N9, it was not possible to estimate LC90 values in the dilution range tested. The lowest LC50 was observed for extract N5, and although extract N10 was the only extract for which the LC90 could be estimated within the range tested, the LC50 was higher than for N5 and N9. These results suggest that substances other than AZA present in the extracts influenced the efficacy, especially up to a certain LC range. In the tests with larvae, no mortality was observed, indicating zero effectiveness of all the extracts tested. The results of the tests with engorged females showed that the neem extracts had acaricide activity, inhibiting egg laying and the larval hatching rate. Complementary studies are necessary to develop new methods to isolate and/or identify other substances besides AZA contained in this plant, to enable using products made from it as acaricides