JASEM ISSN 1119-8362 All rights reserved J. Appl. Sci. Environ. Manage. Dec., 2015 Vol. 19 (4) 569 - 574 Full-text Available Online at www.ajol.info and www.bioline.org.br/ja Effectiveness of the Primextra Gold in controlling weeds of Cucumber (Cucumis Sativus L.) *UGWUNNA R.U 1 , *OCHEKWU, EB 2 . *ANYANWU, DI 3 . Department of Plant Science and Biotechnology, Faculty of Science, University of Port Harcourt. ABSTRACT: The efficacy of Primextra Gold herbicide in controlling weeds in cucumber was evaluated in this research. The experiment was laid out in a randomized complete block design with four replications. Seven weed control treatments – 0.0, 0.25, 0.5, 0.75, 1.0, 1.25 and 1.5 kg a.i/pot – were applied pre-emergent for this study. The dry weight, height of plant, number of green leaves, weed control efficiency, weed persistence index, crop phytotoxicity rating, weed destruction rating, weed count (total number of weeds), weed flora and classification were used to determine the herbicide efficacy and crop safety. Results show that the effects of the treatments were mostly significant; all the treatments caused over 50% injury to the cucumber at all stages except at 7 Days After Treatment. At the end of the experiment, results show that the treatments were highly toxic as they caused up to 100% injury to the cucumber preventing height, dry weight or leaf number measurements to be taken except in pots which received 0.25kg a.i/pot of the herbicide and the control. Weed destruction ratings was over 50% for all of the treatments and at all stages, except for 0.25kg a.i/pot at 21 and 28 DAT. Weed density and dry weight were significantly reduced by the treatments. WCE% recorded was over 50% while WPI was zero (0) for all treatments except 0.25kg a.i/pot. Common weeds observed include Oldelandria corymbosa and Digitario sp. © JASEM http://dx.doi.org/10.4314/jasem.v19i4.1 KEY WORDS: Weed control efficiency, weed persistence index, crop phytotoxicity rating, weed destruction rating and weed count. INTRODUCTION Herbicides are widely used for control of weeds in both agricultural and non-agricultural situations because they provide effective control of weeds (Altland, 2003). With the increasing array of products and the continuing refinement of application equipment, herbicides are effective and practical in a wide variety of weed control situations. (Ashley, et al., 2008). Most herbicides are initially discovered, developed and registered for use in major crops such as corn, soybeans, grains, cottons and sugar beets. Very little, if any crop screening efforts are directed toward minor crop that include high value vegetable crops. There is a limited availability of herbicides for some curcubits (Tickes, 2012; Sosnoskie, et. al., 2013). MacLeod (2001) also reported that as at 1997, only one herbicide was registered for use in cucurbits which controlled only grasses and due to the absence of registered herbicides, “weeds are probably the most important cause of cucurbit yield loss”. According to Shiboleth, et al. (2001), in the past decade, no new herbicides have been labelled and none are known to be under development for cucurbits. Gianessi and Williams (2011) identified the need for subject matter specialists capable of evaluating weed problems and formulating herbicide recommendations on a per country basis. Primextra Gold which is a recently introduced herbicide in Nigeria has not been widely applied by farmers. It is used to control annual grasses and broad leaf weeds in maize, sugar cane, sweet corn and oxabetrinil (Concep safener) treated sorghum. Therefore, in order to expand the range of herbicides available for use in cucumber and provide a potential alternative herbicide, the objective of this study is to analyse the effectiveness of the pre-emergent herbicide, Primextra Gold in controlling weeds of cucumber and to determine its safety for use in cucumber. MATERIALS AND METHODS The field experiment was conducted between February and March, 2013 in the botanical garden of the University of Port Harcourt, Rivers state, Nigeria. The experiment was laid out in a randomized complete block design with four replications (Table 1). Six (6) seeds of cucumber were planted in each container. Cucumber seeds (Cucumis sativus), obtained from the local market were used for the experiment. Primextra Gold was applied postplant preemergence with CO 2 pressurized backpack sprayer. Sufficient quantity of moisture was maintained in the soil at the time of application.