The Study On Phytotoxicity Of Postemergence Application Of2,4-D Butylate Against Maize

2,4-D butylate as auxin herbicide controlling broadleaf weeds in the cornfield, kill the grasseffect and quickly, low toxicity for human, mechanisms of various long-term use of resistant weedsis not easy, for this reason it has been thriving in the stages of the production and application.However, the diversity of sensitivity to the2,4-D butylate is very big between different maizevarieties and different leaf ages, phytotoxicity symptoms will last for a long time, the impact ofseedling stage will still emerge untill the maize tassel. The trial objective is explicit the differentmorphology of different leaf stages, the different sensitivity of different corn variety, and toestablish correlation and path anaysis between the early morphological and the late production.Experiment using9maize varieties of first to four accumulated temperature in Heilongjiangprovince as the test object，2,4-D butylate application at2、4and7leaf stages of maize，the activeingredients dose is0~1620g a.i.�'hm-2, the results showed that:（1）For the test9variety, there were large differences in sensitivity when spray2,4-Dbutylate at different leaf stages. It is safer to spray2,4-D butylate at4leaf stage than2or7leafstage, at this period caused only briefly twisted roll of blade and it can recover late growth, tasselnot enough full, ear and basal of stem grow normally, slightly effect on aerial root but it can growinto the soil. When spray it at2leaf stage, leaves wrinkled lead to the male spike pull out blocked,even the ear deformation, basal of stem grow normally, aerial roots malformed caused fail to growinto the soil. When spray it at7leaf stage, though the effect of leaf and tassel were slightly, but thetassel pull out late, stem nodes intumescent、bended、embrittlement, the injury degree of aerial rootwas the most serious in three stages and fail to grow into soil. The degree of phytotoxicity were allincreased gradually along with the increase of the dose in these three leaf stages（2）The maize varieties tested in this experiment, at different leaf stages sensitivity to thelargest was Demeiya1. Suiyu7, Zhedan37and Dongnong251come second place. The sensitivityto the least were Lvdan1and Xianyu335, Fenghe10, Jidan27and Longdan38.（3）Spray2,4-D butylate at2leaf stage of maize, after7d, the width of the third leaf candirect reflection of the situation of maize tassel. Spray it at4leaf stage, Stem cross coarse candirect reflection of the fresh weight of maize, the width of the fourthly leaf comes second.Spray it at7leaf stage, the width of the seventh leaf, early stage fresh weight and leaf sheath height of the seventh leaf were all direct reflection of the fresh weight of Heading stage of maize,and degree in turn weakens.