金华农区早稻直播田杂草的发生及防除

田间调查表明，早稻直播田发生的杂草有４１种，分属２１个科。其中稗草为优势种，田间出现频度为１００％，二级以上危害田块占５６．４％。局部农区优势种为水莎草或千金子，发生密度高，危害严重。早稻直播田出草顺序依次为稗草、牛毛毡、千金子、矮慈菇、节节菜、鸭舌草、丁香蓼等。稗草出草高峰在水稻播种后５～１５ｄ，其它杂草出草高峰在水稻播后１０～２０ｄ，２５ｄ后杂草停止出苗。播种当天或播后４ｄ内采用４０％直播净６７５～９００ｇ／ｈｍ＾２，对稗草、千金子有特效，总体除草效果可达９５％以上。对水竹叶、双穗雀稗较多田块，采用１０％农美利２９５～３００ｍｌ／ｈｍ＾２，防除效果达９０％以上。

Occurrence of weeds in early direct seeded rice fields and their control in Jinhua, Zhejiang

Results of our investigation showed that there are 41 species of weeds belonging to 21 families in the fields of early direct seeded rice in Jinhua,Zbejiang. Among them, Echinochloa crusgalli is the most important species with 100% of frequency and 56.4% of damage more than the 2nd grade, while in some regions Juncellus serotinus and Leptochloa chinensis are superior to other weeds. The time order for germination of weeds in fields is E. crusgalli, Eleocharis yokoscensis, L. chinensis, Sagittaria pygrnaea, Rotalaindica, Monochoria vaginalis, Ludwigia prostrata. Bamyardgrass has a peak for germination at 5 - 15 d after rice seeded,other weeds at 10- 20 d, and all weeds stop to emergence at 25 d. 40% pretilachlor + bensulfuron-methyl WP used at the dosage of 675 - 900 g/hm2 at 0 or 4 d after rice seeded is very effective on E. crusgalliand L. chinensis, with more than 95% of total efficacy. For Murdannia triquetra and Paspalum distichum, 10% Nominee (bispyribacsodium) SC 225 - 300 ml/hm2 is applied and has more than 90% of the effect.