Harmful and beneficial aspects of Parthenium hysterophorus: an update

Parthenium hysterophorus is a noxious weed in America, Asia, Africa and Australia. This weed is considered to be a cause of allergic respiratory problems, contact dermatitis, mutagenicity in human and livestock. Crop production is drastically reduced owing to its allelopathy. Also aggressive dominance of this weed threatens biodiversity. Eradication of P. hysterophorus by burning, chemical herbicides, eucalyptus oil and biological control by leaf-feeding beetle, stem-galling moth, stem-boring weevil and fungi have been carried out with variable degrees of success. Recently many innovative uses of this hitherto notorious plant have been discovered. Parthenium hysterophorus confers many health benefits, viz remedy for skin inflammation, rheumatic pain, diarrhoea, urinary tract infections, dysentery, malaria and neuralgia. Its prospect as nano-medicine is being carried out with some preliminary success so far. Removal of heavy metals and dye from the environment, eradication of aquatic weeds, use as substrate for commercial enzyme production, additives in cattle manure for biogas production, as biopesticide, as green manure and compost are to name a few of some other potentials. The active compounds responsible for hazardous properties have been summarized. The aim of this review article is to explore the problem P. hysterophorus poses as a weed, the effective control measures that can be implemented as well as to unravel the latent beneficial prospects of this weed

Inter-species comparison of seed dormancy and germination of six annual Asteraceae weeds in an ecological context

To understand germination timing in an ecological context, the response to environmental events that affect seed dormancy is central, and has to be combined with knowledge of germination responses to different circumstances. In this study, seed dormancy, germination, and emergence phenology of six annual co-occurring weedy Asteraceae species were investigated. Three pre-treatments (warm and cold stratification, and dry storage) were tested as possible dormancy affecting environmental events. Seeds were also sown outdoors. Species-specific differences were revealed in analyses. To facilitate general descriptions of dormancy patterns and germination preferences separately, condensed responses to the different possible dormancy affecting treatments and relative germination in different environments were plotted, giving species-specific patterns. Most species exhibited decreased dormancy to two or three pre-treatments. Dormancy was most effectively reduced by cold stratification for three species (Guizotia scabra, Parthenium hysterophorus, Verbesina encelioides), by warm stratification for two (Bidens pilosa, Galinsoga parviflora) and by dry storage for one (Tagetes minuta). All species germinated more when provided with light than in continuous darkness. Temperature levels most suitable for germination varied from low (15/5-20/10°C) for Verbesina encelioides to high (25/15-30/20°C) for Bidens pilosa. It is concluded that, even though the species have different dormancy patterns and germination preferences that suggest different possible distribution ranges, the species achieve similar emergence timing in the field in environments with a pronounced dry period after dispersal and small annual temperature fluctuations.Original publication: Laila M. Karlsson, T. Tamado and Per Milberg, Inter-species comparison of seed dormancy and germination of six annual Asteraceae weeds in an ecological context, 2008, Seed Science Research, (18), 35-45. http://dx.doi.org/10.1017/S0960258508888496. Copyright: Cambridge University Press, http://journals.cambridge.org

Desempenho agronômico do sorgo em função de doses e épocas de aplicação do herbicida 2,4-D Agronomic performance of sorghum as a response to 2,4-D application dosage and times

A cultura do sorgo está inserida no plano atual de manejo dos sistemas agrícolas nos cerrados, todavia são escassos os estudos em campo quanto à seletividade e comportamento da cultura ao herbicida 2,4-D. Objetivou-se neste trabalho avaliar os efeitos do 2,4-D sobre o crescimento das plantas, a produção de fitomassa seca e fitomassa verde e a produtividade de grãos na cultura do sorgo. O experimento foi realizado entre janeiro e maio de 2008, em Nova Xavantina-MT, em Latossolo Vermelho-Amarelo distrófico. O sorgo (cultivar Buster) foi semeado em área cultivada sob sistema de plantio direto, em espaçamento de 0,50 m entre linhas, distribuindo-se 10 sementes por metro. Os tratamentos foram dispostos em esquema fatorial 4 x 4, envolvendo quatro doses de 2,4-D (0, 335, 670 e 1.005 g ha-1) e quatro épocas de aplicação (pré-semeadura, três folhas expandidas, seis folhas expandidas e pré-florescimento). Utilizou-se o delineamento de blocos casualizados com quatro repetições. O controle de plantas daninhas na cultura foi realizado manualmente, com utilização de enxada. Verificou-se efeito fitotóxico à cultura do sorgo pelo 2,4-D aos 15 dias após a aplicação (DAA), independentemente da dose ou época de aplicação. O incremento das doses de 2,4-D provocou redução linear da altura de plantas, acúmulo de fitomassa verde e acúmulo de fitomassa seca, tanto aos 30 DAA quanto no ponto de rolagem. A aplicação do 2,4-D prejudica a produtividade do sorgo, especialmente em doses acima de 1.005 g ha-1 e.a. e em aplicações tardias. De maneira geral, a utilização do 2,4-D em pré-semeadura mostrou-se uma boa alternativa no manejo das plantas daninhas na cultura do sorgo.<br>Sorghum is part of the current plan of agricultural system management for the cer rado. However, few field studies have been carried out on this culture's behavior and selectivity towards herbicide 2,4 D. The objective of this study was to evaluate the effects of 2,4-D on plant growth, dry matter production and green biomass and grain yield in sorghum. The experiment was conducted between January and May 2008 in Nova Xavantina-MT in dystrophic Oxisol. Sorghum (cv. Buster) was sown in a cultivated area under no-tillage, with 0.50 m spacing between rows, and ten seeds distributed per meter. Treatments were arranged in a 4 x 4, involving four levels of 2,4-D (0, 335, 670, and 1.005 g ha -1 ) and four application times (pre-sowing, three fully-expanded leaves, six leaves, and pre-flowering).A randomized block design was used, with four replica tions. Weed control in the culture was performed manually, using a hoe. Toxic effects caused to sorghum by 2,4-D were observed at 15 days after application (DAA), regardless of dose or time of application. The increasing levels of 2,4-D caused a linear reduction in plant height, biomass and green dry matter accumulation, both at 30 DAA as the point of rollover. The application of 2,4-D affected sorghum yield, especially at doses above 1.005 g ha -1 and late applications. In general, the use of 2,4-D in pre-sowing proved to be a good alternative for the management of weeds in sorghum crop