棉花２，４─Ｄ微量中毒症状观察症状主要发生在榆田，幼苗期和成株期均可发病．幼苗期真叶发病，叶片缩小、变厚、叶色略浓，对表面产生２ｍｍ在衣隆起丘疹状凸起（俗称蟾蜍豆），可逐渐扩大，叶脉逐步变成平行线，叶面积减小，叶边缘呈锯齿状、深裂。叶尖变细长、扭曲，... Cotton 2,4 ─ D trace poisoning symptoms Symptoms mainly occur in Yutian, seedling stage and adult stage can be disease. Seedlings of true leaf disease, leaf shrinkage, thickening, leaf color slightly thick, on the surface to produce 2mm in the coat rise pimple-like bumps (commonly known as toad beans), can be gradually expanded, veins gradually become parallel lines, leaf area decreases, Leaf edge serrated, deep cleft. Slender, distorted, ...