Eucalyptus citriodora leaf extract as a source of allelochemicals for weed control in pea fields compared with some chemical herbicides

Two field experiments were established at the Agricultural Experimental Station of the National Research Centre at Nubaria, Beheira Governorate, Egypt to study the herbicidal potential of the leaf extract of Eucalyptus citriodora at 5, 10, 15, 20 and 25% compared to two hand hoeing, unweeded treatments and the chemical herbicides Bentazon + Clethodium, Bentazon + Fluazifop-P-butyl and Butralin on pea plants and associated weeds. The results indicated that two hand hoeing achieved the maximum weed depression as expressed by the dry matter of total weeds. The dry matter of total weeds decreased by 95.08 to 94.77% as compared with unweeded treatment 50 and 70 days after sowing (DAS) followed by Butraline (93.93–94.65%), Bentazon + Clethodium (93.26–94.07%), Bentazon + Fluazifop- -P-butyl (91.82–92.77%) and leaf extract of Eucalyptus at 25% (91.61–91.95%). Furthermore, the reduction in weed development was accompanied by enhanced pea growth and yield. The results revealed that two hand hoeing was the best treatment to increase plant height, shoot dry weight and SPAD value at 50 and 70 DAS. Also, two hand hoeing produced the maximum values of pod length and number of seeds/pod. The results also indicated that Bentazon + Clethodium treatment gave observable values [recorded 72.96% in pod yield (ton ⋅ fed.–1) over that of unweeded control] of number of pod/plant, weight of pod/plant, seed yield/fed and protein percentage. Also, the results revealed great increases in the growth of pea as well as yield due to treatment with E. citriodora dry leaf extract at 25%. [recorded 64.8% in in pod yield (ton ⋅ fed.–1) over that of unweeded control]. So, the results indicated using Bentazon + Clethodium as well as E. citriodora dry leaf extract at 25% to control weeds associated with pea plants. The authors suggested application of E. citriodora dry leaf extract at 25% in controlling weeds associated with pea plants as a safe method that avoids environmental contamination

A study on controlling Setaria viridis and Corchorus olitorius associated with Phaseolus vulgaris growth using natural extracts of Chenopodium album

The effects of water extracts of Chenopodium album leaves and roots on the growth of grass weed (Setaria viridis) and broad leaf weed (Corchorus olitorius) grown with beans (Phaseolus vulgaris) in greenhouse pots were studied in the National Research Centre, Giza, Egypt. In this experiment fresh leaf and root extracts and their corresponding dry leaf and root extracts at different concentrations were used. There were significant inhibitions in the dry weights of S. viridis and C. olitorius by all extracts at the flowering stage of beans and at harvest. The inhibition effect of all C. album extracts on both weeds (dry weight/pot) depended on the extracted plant organ (leaf or root), its fresh or dry form as well as its concentrations. The inhibition caused by the leaf extract was much higher on weed growth than that of root extract. A higher concentration of fresh leaf extract (25%) had the highest significant inhibition effect. The results also indicated that C. olitorius was more sensitive to the extracts than S. viridis. On the other hand, the inhibition effect of the extracts on the growth of both weeds was accompanied by increased bean growth and yield/plant. The analysis of both leaf and root extracts of C. album revealed that the total content of polyphenols and flavonoids in the leaf extract was more than triple that of the root extract. The results suggested that the fresh leaf extract of C. album may be a possible tool for the development of weed control using natural herbicides

Allelopathic effects of Eucalyptus citriodora on amaryllis and associated grassy weed Efeitos alelopáticos do Eucalyptus citriodora sobre amarílis e em gramíneas daninhas associadas

A Petri dish assay was carried out for screening different concentrations of aqueous extracts of fresh and dry leaves of Eucalyptus citriodora on germination and seedling growth of wild oat weed (Avena fatua). Seed germination, root and shoot length of wild oat exhibited different degrees of inhibition according to the concentration of the aqueous extract. Maximum inhibitions of germination percentage, root and shoot length were recorded when using 25% fresh leaf extract. Based on this preliminary work (Petri dish assay), studies were conducted under greenhouse conditions at the National Research Center, Egypt, in the two winter seasons of 2006/2007 and 2007/2008 to evaluate the effects of foliar and soil treatments of aqueous extracts of Eucalyptus citriodora fresh and dry leaves on wild oat weed as well as on the growth and flowering of amaryllis (Hippeastrum hybridum), compared with the recommended dose of the herbicide tralkoxydim. Amaryllis fresh and dry weights as well as flowering increased significantly when treated with the previous extracts, especially the fresh leaf extract. However, the fresh and dry weights of wild oat were significantly reduced by the aqueous extracts, either fresh or dry, indicating phytotoxic effects. Tralkoxydim caused complete inhibition of wild oat as compared with the control. The studies involved estimation of the endogenous contents of total phenols in weed. With all the treatments, the inhibitory effects on weeds were correlated with accumulation of the internal contents of total phenols, compared to their respective controls. The amount of phenols correlated well with the weed's growth performance. This study establishes the effect of the aqueous extracts on the weed wild oat, associated with amaryllis, which may serve as a tool in establishing their herbicidal potential.<br>Um experimento em placas de Petri foi realizado para a seleção de diferentes concentrações de extratos aquosos de folhas frescas e secas de Eucalyptus citriodora na germinação e no crescimento inicial de aveia-selvagem (Avena fatua). A germinação da semente, a raiz e o comprimento da brotação apresentaram diferentes graus de inibição, de acordo com a concentração do extrato aquoso. As maiores porcentagens de inibição da germinação, de raiz e de comprimento de brotação foram registradas com extrato fresco das folhas a 25%. Com base no trabalho preliminar (experimento em placa de Petri), foram conduzidos estudos na estufa do Centro de Pesquisa Nacional, Egito, em duas estações de inverno: 2006/2007 e 2007/2008. Nesse local, foram avaliados os efeitos de tratamentos foliar e do solo de extratos aquosos das folhas frescas e secas de Eucalyptus citriodora na aveia-selvagem, assim como no crescimento e no florescimento da espécie Hippeastrum hybridum, em comparação com a dose recomendada do herbicida tralkoxydim. Os pesos frescos e secos do amarílis sofreram aumento significativo, bem como o florescimento, quando tratados com os extratos, principalmente com a pulverização do extrato das folhas frescas. Entretanto, os pesos frescos e secos da aveia-selvagem foram reduzidos significativamente pelos extratos aquosos, tanto frescos como secos, indicando intoxicação. O herbicida tralkoxydim causou a inibição completa de aveia-selvagem em comparação ao controle. Os estudos envolveram a avaliação dos índices endógenos de fenóis totais na espécie daninha. Em todos os tratamentos, os efeitos inibitórios nas espécies daninhas foram correlacionados com o acúmulo de índices internos dos fenóis totais, comparados aos respectivos controles. Constatou-se boa correlação entre a quantidade de fenóis e o desempenho do crescimento na espécie daninha. Este estudo estabeleceu o efeito dos extratos aquosos sobre a espécie daninha aveia-selvagem associada ao amarílis, o que pode servir como ferramenta para estabelecer seu potencial herbicida