Survey Of Weeds Research Articles

Plantas daninhas em mandiocais (Manihot esculenta Crantz) na região mineradora de Diamantina (Alto Jequitinhonha), Minas Gerais

Realizou-se um levantamento das plantas daninhas de mandiocais na região Mineradora de Diamantina (Alto do Jequitinhonha) em Minas Gerais, avaliando-se a composição florística e a estrutura da flora daninha. Percorreram-se os municípios mais representativos desta microregião - Carbonita, Itamarandiba e Capelinha - amostrando as lavou ras indicadas pelos técnicos da EMATER - Empresa de Assistência Técnica e Extensão Rural, coletando e anotando o grau de abundância e a frequência das espécies invasoras, as quais, posteriormente, foram identificadas e na sua maioria depositadas no Herbarium ESAL, da Escola Superior de Agricultura de Lavras, MG. Constatou-se a presença de 45 espécies pertencentes a 19 famílias, sendo 16 dicotiledôneas, 2 monocotiledôneas e 1 pteridóphyta. Destacaram-se as famílias Compositae, Gramineae, Malvaceae, Leguminosae, Rubiaceae e Convolvulaceae e as espécies Acanthospermum australe, Sida rhombifolia e Borreria alata.

A survey of grass weeds in cereals in central southern England

SummaryA survey of grass weeds in cereals in nine areas of central southern England was made in summer 1981 with the primary purpose of determining the importance of Bromus sterilis. A total of 1477 fields of winter wheat, 715 of winter barley and 434 of spring barley were assessed by visually scoring the whole field for grass flower heads. In all, 19 species were found; their levels of infestation were scored. In winter cereals the most frequent species were Avena spp. in 32% of fields. Agropyron repens in 24%, Poa trivialis in 22% and Alopecurus myosuroides in 19%. Bromas sterilis was next most frequent in 9%. In spring barley the two most frequent species were Agropyron repens in 53% of the fields and Avena spp. in 52%. The third most frequent was Alopecurus myosuroides in 1 1%. Bromus sterilis was recorded in 12% of winter wheat and 4% of winter barley crops, but did not occur in spring barley. Of the 206 fields where it was present it occurred throughout the field in only 82 and it was confined to the headlands in the remainder.

Plantas invasoras da cultura de arroz (Oryza sativa L.) no Estado de São Paulo: 2 - monocotiledôneas

Foi realizado um levantamento das plantas invasoras na cultura do arroz, concentrado nas regiões com maior área cultivada no Estado de São Paulo. Cada uma das espécies levantadas foi estudada em seu ciclo, porte, fenologia e modo ou modos de reprodução. O hábito de cre sc imento herbáceo, o ciclo anual, o florescimento e frutificação nos meses mais quentes do ano e a reprodução através de sementes foram preponderantes. Cada gênero representado por mais de uma espécie mereceu a confecção de chave analítica auxiliar objetivando oferecer algum subsídio para a identificação da espécie em sua primeira fase de desenvolvimento. Foram levantadas as sinonímias científica e vulgar e, sempre que possível, localizada a etimologia do termo que se pre stou à nomenclatura genérica e específica. De cada espécie é fornecida uma diagnose da plântula além da ilustração planificada, tornando, portanto, mais fácil o reconhecimento da mesma. Das seis famílias monocotiledôneas encontradas, num total de 26 espécies identificadas, quantitativamente mereceram destaque as seguintes: Gramineae, Cyperaceae e Commelinaceae.

A preliminary survey of arable weeds in Britain

Summary:Details and results are given of the first of two surveys, which are designed to measure the changes taking place in the incidence of forty species of arable weeds in Britain.

An agro‐economic survey of the weeds and weeding practices in cassava (Manihot esculenta Crantz) in Colombia

Summary:A survey of weeds and weeding practices was carried out by a team of agricultural economists and agronomists on 283 farms in five Cassava growing regions of Colombia at three times during a cropping season.Seventy‐one to 78% of all weed species present were broadleaved species. As cassava grew older, grass species were present to a greater and sedge species to a lesser relative frequency. Surprisingly Pteridiumaquilinum (L.) Kuhn was the most frequently listed species and Bidens pilosa L. and Cyperus rotundus L. were other frequent problems. Regional variations in the most frequently encountered species were found but several of the weeds were common to many zones. The most frequently encountered species did not usually have the highest plant populations. Most of the annual grasses, sedges and broadleaf weeds found can be controlled by currently recommended herbicides for cassava but further research is needed on Imperata cylindrica (L) Beauv., Melinis minutlftora Beauv., P. aquilinum and Sida spp.The average number of manual weedings was 3.3 per crop, occupying 48 man‐days/ha which is 50% of the total labor requirements for cassava production, and more than one‐third of the total costs. Reasons for not using herbicides were (1) relative costs of herbicides and labor. (2) lack of information, (3) lack of capital, (4) right herbicides were not available, and (5) herbicides were not available in small packages.This survey has usefully identified new field problems and has suggested further research programs to solve them.

Weed Problems in Tree Crops in Nigeria

Abstract A preliminary survey of weeds of cocoa, kola, coffee and cashew was made to identify problem weeds in order to understand their distribution and later formulate appropriate methods for their control. The survey was conducted in experimental plots, plantations and small farms. Whereas certain weeds are common to all the four tree crops, some appear to be associated with a particular crop. Many of the weeds are annuals which complete two or more life cycles a year and have a tremendous capacity for seed production. Others are short-lived perennials and perennials which are very difficult to control or eradicate. Rapid and vigorous growth of early-season weeds starts annually with rains in February or March and their mode of regeneration varies in the different species. Tree crops planted under clear-felled conditions are subjected to serious weed competition and frequent weeding is necessary to ensure the successful establishment of young seedlings.