许多苹果砧木的地上部都发生日灼病,在这个病区内有根系的增生。树体生长的时候,这些病疤也可以扩大,在树干上形成凹陷。这样就阻碍了维管束的输导作用,削弱了树势,同时还起到了为害虫的幼虫提供藏身之地的作用,例如某些蛀虫类就是这样。同时这儿也是火疫病侵入的通道。现在已经可以肯定,当砧木露出地面以上时,MM111、MM106、M7和 M26等砧木是极容易发生日 Many apple rootstocks have sunburns in the shoots, and there is root proliferation in this ward. When the tree grows, these scars can also be enlarged to create depressions in the trunk. This hinders the transport of vascular bundles, weakens the tree’s potential and also serves as a hiding place for pest larvae, as is the case with certain borers. At the same time, it is also a passage where fire blight invades. It is now certain that stocks such as MM111, MM106, M7 and M26 are extremely prone to occur when stocks are above ground level