（2）在同一浓度下，随着处理时间的增加，枣果黑顶病发病率逐渐降低，在2

(2) At the same concentration, as the treatment time increases, the incidence of black top disease in jujube fruit gradually decreases, reaching the lowest value in 20 days; the activity of three antioxidant enzymes (SOD, POD, CAT) in jujube fruit, vitamin C The content and calcium content gradually increase, and then tend to level off. Among them, Ca1 reached its maximum value on the 12th day, and Ca2 and Ca3 reached its maximum value on the 16th day. This result shows that during the prone period of jujube fruit, it is necessary to continuously spray calcium on jujube fruit to increase antioxidant enzymes (SOD, POD, CAT) activity, and the calcium content of jujube fruit, reduce the incidence of black top disease. As the incidence is negatively correlated with calcium content, increasing the calcium content of jujube fruit and the activity of antioxidant enzymes (SOD, POD, CAT) can reduce the occurrence of diseases.

(2) At the same concentration, with the increase of treatment time, the incidence of black-top disease gradually decreased, reaching the lowest value in 20d, and the activity, vitamin C content and calcium content of the three antioxidant enzymes (SOD, POD, CAT) in the fruit gradually increased, and then leveled off. Ca1 reached the maximum on the 12th day, Ca2 and Ca3 reached the maximum on the 16th day, the results show that in the period of easy onset of the fruit, it is necessary to continuously spray calcium on the fruit to improve the activity of antioxidant enzymes (SOD, POD, CAT), calcium content of the fruit, reduce the incidence of black top disease. Because the incidence is negatively related to calcium content, the occurrence of disease can be reduced by increasing the calcium content and antioxidant enzyme (SOD, POD, CAT) activity.

(2) at the same concentration, the incidence rate of black top disease gradually decreased and the lowest value reached 20d at the same concentration. The activities of three antioxidative enzymes (SOD, POD, CAT), vitamin C and calcium content increased gradually and then tended to be gentle. Ca1 reached the maximum value on twelfth days, and Ca2 and Ca3 reached the maximum on the sixteenth day. The results showed that calcium was needed to increase the activity of antioxidant enzymes (SOD, POD, CAT), calcium content in jujube fruits and reduce the incidence rate of black top disease in jujube fruit during the susceptible period. Because the incidence rate is negatively correlated with calcium content, the occurrence of disease can be reduced by increasing calcium content and antioxidant enzyme activities (SOD, POD, CAT).