69 EFFICACY AND ECONOMICS OF HERBICIDES AGAINST NARROW AND BROAD-LEAVED WEEDS OF WHEAT A. Hossain, M. A. S. Chowdhury, P. K. Malaker, M. S. N. Mandal and M. A. Z. Sarker ABSTRACT A field experiment was conducted at Wheat Research Centre, Dinajpur (25°38´ N, 88°41´ E and 38.20 meter above sea level), Bangladesh during the period from December 2008 to April 2009 to determine the effects of some selected herbicides on narrow and broad-leaved weeds, yields and yield components of wheat. The herbicides used were Affinity 50.75WP @1.25 kgha -1 , Hammer 24EC @ 100 mlha -1 , 2, 4-D Amine @ 1200 mlha -1 , U46 @ 1400 mlha -1 , Lintur 70WG @ 100 gha - 1 . Weedy check and hand weeding were also included for comparison. All the herbicides were applied as post emergence at 30 days after sowing. Eighteen weed species belonging to 11 families were identified in the experimental field. Of these 6 species were under narrow-leaved and 12 species under broad-leaved group. The population of broad-leaved weeds dominated over the narrow-leaved species. The family Poaceae was major under narrow-leaved group, while Oxalidaceae, Rubiaceae, Solanaceae and Chenopodiaceae were the predominant families under broad-leaved weeds. All herbicides provided with good control against broad-leaved, but not the narrow-leaved weeds except Lintur. Hammer and 2, 4- Amine could not control narrow-leaved weeds at all. Among the herbicides, Affinity caused the highest weed mortality followed by Lintur, Hammer, U46 and 2, 4-D Amine. When weed control efficiency is considered, Lintur performed the best followed by Affinity, U46, Hammer and 2 4-D Amine. Economic analysis revealed that Affinity gave the highest profit followed by Hammer and 2, 4-D Amine. Considering weed mortality, weed control efficiency and economic benefit, Affinity is the best. However, Hammer, 2, 4-D Amine and U46 may also be recommended for weed control in wheat. Lintur was also found profitable, but may not be suggested because of its phytotoxic effect on wheat plants as symptomps of phytotoxicity observed on the foliage and spikes under field condition. Key words: Weed control efficacy, economics of weed control, herbicides, weeds, wheat. INTRODUCTION Wheat (Triticum aestivum L.) is the foremost among cereals and indeed among all crops, as a direct source of food for human beings. In Bangladesh it is the second major cereal crop next to rice. But the average yield of wheat is lower than those of other wheat growing countries of the world (Islam, 1997). Weed infestation is one of the main causes of low yield of wheat in Bangladesh, and it reduces yield by 29 to 47% in the crop (Mamun and Salim, 1989). Farmers of Bangladesh are usually reluctant to control weeds in wheat fields, and those who control the weeds in their fields usually do using manual labour or hand weeding, which is not economic. Hand weeding is also laborious and time consuming; sometimes farmers are unable to hire costly labour at the peak period due to high demand of labours for other competitive Rabi crops like potato, Boro rice and vegetables. Therefore, chemical weed control is gaining popularity among the farmers. The choice of best herbicide, proper time of application and proper dose are important considerations for lucrative returns. Application of herbicides at 25-30 days after sowing was found most effective in India in decreasing dry matter of weeds and increasing grain yield in wheat (Prasad and Singh, 1995). The present study was undertaken to assess the effectiveness of some selected post-emergence herbicides and their economics in controlling narrow and broad-leaved weeds in wheat. Wheat Research Centre, Bangladesh Agricultural Research Institute, Nashipur, Dinajpur-5200, Bangladesh Bangladesh J. Weed Sci. 1(1): 71-79, June 2010