Study of chemical stability for chlorothalonil and their fungicidal effect against Fusarium solani and Botrytis cinerea.

This study investigated the degradation of two chlorothalonil formulations [Chlorcal ۷۰% Wettable Powder (WP) and Open ۷۲% Suspension Concentrate ۷۲% (SC)]. The tested fungicides were stored at ۵۴ ± ۲°C for ۱۴ days. During the different storage periods, samples were taken after ۱, ۳, ۷, and ۱۴ days to determine physical properties, evaluate the chemical stability of the active ingredient: Hexachlorobenzene as impurities by HPLC and fingerprint (GC/MS and IR), as well as the evaluation of their efficacy, by testing them against the mycelial growth of Fusarium solani and Botrytis cinerea under in vitro condition. The results indicated that Open ۷۲% SC was the most effective fungicide against F. solani and B. cinerea it recorded the lowest EC۵۰ value of ۲۸.۴ and ۴۶.۸ ppm respectively, followed by Chlorcal ۷۰%WP with EC۵۰ values of ۴۲.۹ and ۵۹.۴ ppm respectively. On the other hand, the effectiveness of tested fungicides deteriorated as the result of storage at ۵۴ ± ۲ ºC for ۱۴ days with EC۵۰ values increased from ۲۸.۴ to ۱۳۰.۹ and ۴۶.۸ to ۲۷۸.۱ in the case of Open ۷۲% SC against F. solani and B. cinerea respectively, while the degradation efficiency of Chlorcal ۷۰%WP was decreased at storage with EC۵۰ values from ۴۲.۹ to ۸۹.۴ and ۵۹.۴ to ۱۴۵.۳ against these two fungi respectively. Chlorcal ۷۰%WP was more stable at during storage and less effective against fungal pathogens and determination of chemical content (total soluble sugar; total protein; free amino acids) and some enzymes (amylase and catalase) activities of mycelium fungi. Potato dextrose (PD) media treated with chlorothalonil formulations induced a significant decrease in all components in each fungus except the catalase enzyme in the case of B. cinerea. The obtained results showed that active ingredients were ۶۹.۸۲%, ۷۱.۹% and reached ۶۹.۳%, and ۷۰.۷۵% after ۱۴ days of storage at ۵۴ ± ۲ ºC for Chlorcal ۷۰% WP, Open ۷۲% SC, respectively. Also calculated half-life (T۰.۵) values for Chlorcal ۷۰% WP, Open ۷۲% SC were ۱۳۸۲.۰۷ days and ۶۱۴.۰۳۵ days, respectively. This result refers that Chlorcal ۷۰% WP is more stable than Open ۷۲% SC after storage at ۵۴ ± ۲ oC for ۱۴ days, whereas the amount of hexachlorobenzene was within the FAO limits for all sources before and after storage. Then the other tested GC / MS was used for the degradation of chlorothalonil fungicide, the two major degradation products in chlorothalonil were ۲,۵,۶-trichloro- ۴- hydroxyisophthalonitrile and ۲,۴,۶-trichloroisophthalonitrile.

کلیدواژه ها:

Fungi ، Fungicides ، Chlorothalonil ، Hexachlorobenzene ، IR ، GC/MS ، Chemical stability ، Physical properties ، Antifungal activity ، Chemical composition ، Enzyme