Open-air grapes are generally bagged half a month after physiological fruit setting, and can be bagged as soon as possible according to the situation, but not too late. If it is in the south, bagging should be done as soon as possible after fruit thinning, and it can be delayed slightly in the north, but it is best to bag when the fruit grows to the size of beans, but it should not be too late, and the latest bagging time should not be later than the second fruit expansion period.