Tool For Weed Control Research Articles

Inheritance of resistance to pendimethalin herbicide induced stem damage in soybean

Selective herbicides are valuable weed control tools; however, selectivity is not always complete, resulting in crop damage. Stem breakage, lodging, and enlarged hypocotyls (brittle bean syndrome) limit yields of soybean [Glycine max (L.) Merr.] genotypes treated with pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine]. Developing genotypes with resistance to pendimethalin injury would eliminate or reduce this problem. Genetic studies were conducted to determine the inheritance of resistance to pendimethalin induced stem damage. The F2:3 progeny of crosses involving resistant ('Asgrow A4715' and 'Flyer') and susceptible (`Essex' and K87-7-95) genotypes were screened in a greenhouse. Each genotype was treated with 1.68 kg ha-1 pendimethalin preemergence and irrigated as needed. Plants were scored at V4 for stem breakage. Progeny distributions indicated that resistance to brittle bean syndrome damage behaved as a quantitative trait. Dominance for stem breakage was expressed in the population of A4715 × Essex. Flyer was more sensitive to herbicide damage than Asgrow A4715 because it has fewer genes for resistance or different alleles. The F2:3 variance component heritability estimates ranged from 0.19 to 0.52. Gain from selection for resistance to pendimethalin injury is possible, and resistant progeny can be recovered from segregating populations.

Resistência de biótipos de Euphorbia heterophylla l. Aos herbicidas inibidores da enzima ALS utilizados na cultura de soja

Os herbicidas constituem-se na principal medida de controle de plantas daninhas na cultura de soja; no entanto, a pressão de seleção causada pelo uso contínuo de produtos com o mesmo mecanismo de ação pode provocar a seleção de biótipos resistentes, como ocorreu com Euphorbia heterophylla L., que se mostrou resistente aos herbicidas inibidores da enzima acetolactato sintase (ALS) em áreas dos Estados do Paraná e Rio Grande do Sul. Para comprovar possíveis novos casos, bem como alternativas para prevenção e manejo, coletaram-se sementes de plantas de E. heterophylla L., na região de Assis (SP), que sobreviveram a tratamentos, em que esses herbicidas foram sistematicamente aplicados nos últimos anos. Desenvolveu-se o experimento em casa de vegetação, comparando-se o biótipo resistente ao suscetível, quando submetido aos diversos herbicidas aplicados em pós-emergência. Aplicaram-se quando as plantas encontravam-se no estádio de duas a quatro folhas verdadeiras, nas doses zero, uma, duas, quatro e oito vezes a recomendada. Aos 20 dias após a aplicação, avaliaram-se os parâmetros relativos ao controle e produção de fitomassa epígea visando ao estabelecimento de curvas de doses-resposta, à obtenção dos fatores de resistência com base nos valores da DL50 e GR50, e à verificação da ocorrência de resistência múltipla. O biótipo resistente apresentou diferentes níveis de resistência aos herbicidas chlorimuron-ethyl e imazethapyr, demonstrando resistência cruzada aos inibidores da ALS dos grupos das sulfoniluréias e imidazolinonas. No entanto, foi eficientemente controlado nos tratamentos com fomesafen (250 g.ha-1), lactofen (120 g.ha-1), flumiclorac-pentil (40 g.ha-1), glufosinato de amônio (150 g.ha-1) e glyphosate (360 g.ha-1).

Effects of red clover decomposition on phytotoxicity to wild mustard seedling growth

Previous studies have suggested that phenolics from legume green manures may contribute to weed control through allelopathy. The objective of this study was to determine how decomposition of red clover ( Trifolium pratense L.) residue affects phytotoxicity to a weed species, wild mustard ( Sinapis arvensis L.). Red clover (1.25 g), 30 g acid washed sand, and 5 ml of microbial inoculant were incubated in the dark at 14°C. The incubations were conducted in sand to allow the determination of decomposition phytotoxicity effects without being confounded by soil sorption effects. Aqueous extracts were collected at 0, 1, 2 and 5 weeks. The extracts were analyzed for dissolved organic carbon (DOC) and phenolic carbon (PhC). Phytotoxicity of the extracts was estimated by comparing root elongation under sterile laboratory conditions. The red clover extract significantly reduced radicle growth in the bioassay, but there was no significant change in the degree of phytotoxicity over the 5-week decomposition period. Although the concentration of DOC decreased with increasing decomposition, the PhC concentration was not significantly affected. This suggests that in the absence of soil sorbants, the phytotoxic compounds are stable throughout the 5-week incubation period and are phenolic in nature. This study demonstrates that the potential exists for using legume green manures to be a component of a sustainable weed management system, but indicates that soil characteristics need to be factored in evaluating the potential for this weed control tool.

Rejection of Fusarium pallidoroseum as a Biological Control Agent of Mimosa invisa in Upland Rice

Fusarium pallidoroseum , isolated from diseased Mimosa invisa in the Philippines, provided excellent control of M. invisa seedlings when applied as a foliar spray of the crude culture filtrate in laboratory and field trials. The effect was immediate contact action, causing rapid desiccation of treated tissues because of the production of toxin(s). The cell-free filtrate of F. pallidoroseum was more virulent than the crude filtrate. Seedlings at the cotyledon stage and older 3- to 4-leaf seedlings escaped the phytotoxin action of F. pallidoroseum and regrowth occurred. Inoculum was readily produced on milled rice and remained virulent for at least six months under room condition storage. Culture filtrates of F. pallidoroseum caused disease symptoms on a broad range of plant species. Most plants, however, expressed only light infection, while Mimosa invisa , M. pudica and Cucumis melo (cantaloupe) were severely damaged by the isolate. Symptoms were observed on some upland rice cultivars, but affected rice plants outgrew the effects. Mycotoxins are produced by isolates of F. pallidoroseum , but the health risk associated with the use of F. pallidoroseum as a weed control tool is not known. Until the health risk is known and documented, the possible use of F. pallidoroseum as a control strategy for M. invisa should be deferred.

Initial Technical and Economic Comparisons of Different Farming Systems in Ontario, Canada

ABSTRACT Three different farming systems for Ontario, Canada were compared from technical and economic standpoints. The conventional system farms relied upon government-prescribed rates of synthetic herbicides for weed management. Reduced-input system farms used crop rotations and tillage systems as partial substitutes for synthetic herbicide inputs. Organic system farms proscribed the use of synthetic herbicide treatments entirely, relying instead on crop choices and sequences, tillage methods, animal manure composting, and other management tools for weed control. All farm types had similar natural resource endowments, but conventional farms were the most specialized and operated the largest land base, while organic farms were the most diversified and smallest. Organic farmers expended the most time, effort and operating capital in controlling weeds, despite the lack of any expenditures on synthetic herbicides. However, organic farmers spent the least on seeds, overall labour and overall machinery operat...

Vegetation management practices in plantation forests of Australia and New Zealand

Radiata pine (Pinusradiata D. Don) is the predominant species in plantation forests of Australia and New Zealand. Removal or suppression of noncrop vegetation is often carried out to enhance crop growth and survival by reducing competition for water, light, and nutrients. Other reasons for vegetation removal include microclimate modification, providing access into stands, and fire hazard reduction. Many studies have demonstrated large increases in crop growth from removing noncrop vegetation. Vegetation management can also mean introducing noncrop species to improve site quality, to suppress unwanted species, or to provide fodder for grazing. While herbicides are still the most widely used weed control tool, nonchemical methods are of increasing importance. The role of machinery is likely to increase in both countries as the use of fire for vegetation management and general site preparation declines. To calculate the long-term cost–benefit of vegetation management, a better understanding of the crop growth response to these treatments is essential. This requires experiments that focus on the role of both crop and noncrop species in hydrological and nutrient cycles. Personal computer based decision support systems are likely to play an increasing role as an aid to cost-effective vegetation management decision making.

Evaluation of pre‐emergence herbicides for establishing coffee

Abstract Two field experiments were conducted to determine the safety of repeated applications of several pre‐emergence herbicides in coffee from the recently transplanted stage to 1 year old. Oryzalin and oxyfluorfen had at least a four‐fold selectivity margin to coffee at two locations; these herbicides had a greater safety margin than simazine, atrazine and diuron, which all injured young coffee at 4.5 kg a.i./ha. Oxyfluorfen, atrazine, simazine and diuron provided better control of the weed species than oryzalin. Oxyfluorfen did not provide complete control of weeds in the Compositae family which were completely controlled by atrazine and diuron. Oxyfluorfen and oryzalin were shown to be effective management tools for weed control in young coffee because of their excellent selectivity.

Clinical Notes on Cases of Azoturia, Hæmoglobinuria and Acorn Poisoning.

The development and implementation of integrated weed management (IWM) strategies that provide good weed control while reducing dependence on herbicides, and preferably without having side effects on the overall system economic performance, is still a challenge that has to be met. In 2011 and 2012, nine on-farm experiments (i.e., real field conditions on commercial farms, with natural weed flora) were conducted in three important European maize producing regions-countries, which represent the range of climatic and edaphic conditions in Europe, to evaluate the efficacy of different locally selected IWM tools for direct weed control in maize vs. the conventional approach (CON) followed by the farms. The IWM tools tested were: (1) early post-emergence herbicide band application combined with hoeing followed by a second hoeing in Southern Germany, (2) early post-emergence herbicide broadcast application when indicated by a predictive model of weed emergence after performing one scouting in the field to supply data for the model, followed by hoeing in Northern Italy, and (3) tine harrowing at 2–3rd leaf stage of maize and low dose of post-emergence herbicide in Slovenia. Results showed that the IWM tools tested in the different countries: (1) provided sufficient weed control without any significant differences in yields, (2) greatly reduced maize reliance on herbicides, and (3) IWM implementation was economically sustainable as no significant differences in gross margin were observed in any country compared to CON.