Effects Of Mancozeb And Chlorothalonil Mixture On The Postharvest Inhibition Of Apple Bitter Rot And Apple Fruit Qualities

Apple bitter rot, which is also called apple decay, has been happening in most areas of our country and belongs to one of the most important diseases on apple. In the past, the research were mainly focused on the cue during apple growth, while, little was aimed at the postharvest disease inhibition. In this article, two non-systemic fungicide, mancozeb and chlorothalonil, were firstly evaluated for their protection effects on apple from bitter rot.Then, the best mixture combination ratio of them was screened out. Because that the fungicides may have effects on the quality of postharvest apples, some of the inner qualities were measured after treatment. Lastly, though the screened fungicide mixture showed great protection effects on apple bitter rot, the residues should be paid attention for. So, two concentrations of 10 and 30 mg/L were applied to monitor the dynamics of residues metabolism, the results of which may guide the rational use of these fungicides. The results were as follows :(1) The EC50 of mancozeb was 14.31 mg/L and that of chlorothalonil was 6.18 mg/L.Both of these two fungicides showed great inhibition effects on apple bitter rot.(2) Using interaction measurement, the highest inhibition rate of 65.9% was observed when the mix ratio of mancozeb and chlorothalonil was 80 : 20(weight ratio : 11.45 :1.24) with significant synergistic effects.(3) Under the optimized ratio, 12.69% mancozeb and chlorothalonil mixture was made with EC50 of 10.58 mg/L and EC90 of 29.53 mg/L.(4) Higher concentration of the mixture decreased the contents of soluble solids, while,increased the acid contents and polyphenols. Middle concentration of the mixture improved the soluble sugar contents, however, lower or higher concentration both resulted in the decrease of soluble sugar content.(5) The residue of mancozeb was high both on the surface on inside of the fruit, but the degradation rate was quick. Though the residue of chlorothalonil was low, the degradation rate was slow.This research innovatively introduced two non-systematic fungicides for postharvest apple protection. The results showed that though the chosen fungicides were non-systematicand had great protection effects on bitter rot, the residues were observed inside the fruit and partially affect some of the inner qualities. In summary, the method described in this article is suitable for the situation of long time conservation, but not short time storage.