苹果树改劣换优必须注意防病随着科学技术的发展和人民生活水平的提高，苹果树改劣换优、更新换代势在必行。但如不注意防病，改接后就不能迅速投入生产，因而影响产量，减少收入。故改劣换优工作要想达到预期目的，必须做好防病工作。１．优良品种的接穗必须从优质健壮的... Change the apple tree must pay attention to disease prevention and disease prevention With the development of science and technology and people’s living standards, apple trees change the best, upgrading is imperative. However, if we do not pay attention to preventing diseases, we will not be able to put them into production immediately after we have switched over them, thus affecting output and reducing revenue. Therefore, changing the excellent work in order to achieve the desired goal, we must do a good job in disease prevention. 1. Excellent varieties of scion must be from the ...