Commelina diffusa is a colonising species of banana orchard habitats in St. Vincent in the Windward Islands of the Caribbean. In the present study, the population dynamics of C. diffusa were investigated in response to mechanical weed management with either a rotary string trimmer or glufosinate in ruderal and banana habitats. The study focused on density and size distribution of the weed over time and their response to two weed management strategies. The population dynamics of C. diffusa differed between the two habitats. Seedling establishment appeared to be an important factor influencing the dynamics of C. diffusa in banana orchards as there was little recruitment of seeds with less flower production compared with ruderal habitats where plants produced more flowers. Plants of C. diffusa in the banana orchard habitat had a longer growth cycle. In the banana orchard habitat, the C. diffusa population was greater and the plants were shorter with mechanical management than in areas treated with glufosinate. The results suggest that it is possible to manipulate the dynamics of C. diffusa in banana orchards as there is less chance of seed recruitment. Further research is necessary to refine an IPM approach for the management of C. diffusa. 1. Introduction C. diffusa occurs in ruderal and agricultural habitats in the Windward Islands. In the agricultural habitat of St. Vincent and the Grenadines, it is commonly found in banana but it also grows extensively in root crops such as dasheen (Colocasia esculenta (L.) Schott) (personal observation, November 2003). C. diffusa has gained noxious weed status in the Windward Islands for a number of reasons. Banana growers in the Windward Islands since the early 1970s have relied primarily upon the herbicides 2,4-D, paraquat, and glyphosate. Heavy reliance and continuous use of these synthetic herbicides have resulted in a number of problems, including the development of herbicide-resistant biotypes of C. diffusa [1]. Since the introduction of fair trade (Fair trade is an organized social movement and market-based approach that aims to help producers in developing countries make better trading conditions and promote sustainability. The movement advocates the payment of a higher price to producers as well as higher social and environmental standards.), in 2002, with its minimal or prohibited use of herbicides, farmers have controlled weeds manually, using the cutlass or using the “rotary string trimmer.” Use of the cutlass and rotary string trimmer has intensified the problem of C. diffusa by exacerbating the spread of
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