Evaluation and Determination of Minimum Inhibitory Concentration of Fungicides against Root Rot Pathogen of Citrus (Phytophthora nicotianae)

Author: Sanhita Malvi, Jayant Bhatt, Ashis K. Das, Pratik Pali, Ashok Kumar, Aatmika Chouhan and Sanjay Kharte

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Abstract

Phytophthora species are one of the most devastating oomycetes causing root rot of citrus. The pathogen was earlier controlled by metalaxyl (phenylamide), but from 1980’s, development of resistance to phenylamides have been reported. In the present study, efficacy of ten different fungicides, (7 systemic, 2 contact + systemic and 1 contact fungicides) was evaluated against the mycelial growth of Phytophthora nicotianae by poisoned food technique. The result revealed that all the tested fungicides were significant in controlling the mycelial growth as compared to control. Metiram 44% + Dimethomorph 9%, Metalaxyl 4% + Mancozeb 64%, Mandipropamid 23.4%, Fluopicolide 39.5%, and Fluopicolide (5.53% w/w) + Propamocarb hydrochloride (55.3% w/w) exhibited complete inhibition at 250, 500 and 1000 ppm. The least mycelial inhibition was exhibited by cyazofamide (33.85%, 43.85% and 62.31% at 250, 500 and 1000 ppm respectively. To study the minimum inhibitory concentrations (MIC’s) of fungicides, the concentrations were increased/decreased. The response of fungicides on mycelial growth of P. nicotianae was highly variable. Based on MIC’s, the fungicides were grouped into three groups (Group I, II and III). The MIC of Metiram 44% + Dimethomorph 9% was 10 ppm, followed by Metalaxyl 4% + Mancozeb 64%, Mandipropamid 23.4%, Fluopicolide 39.5%, and Fluopicolide (5.53% w/w) + Propamocarb hydrochloride (55.3% w/w) was 30 ppm and were placed in Group I. The MIC of Fosetyl Al, Chlorothalonil 50% + Metalaxyl 3.75% SC and Phosphorous acid was 1000 ppm and was placed in Group II. Azoxystrobin 20% + Difenoconazole 12.5% SC (2000 ppm) and cyazofamide (8000 ppm) were placed in Group III.

Keywords

Citrus, Root-rot, Phytophthora nicotianae, Fungicides, in-vitro evaluation, Dimethomorph

Conclusion

The use of fungicides in the laboratory and field depends on their in-vitro efficacy at minimal and economically acceptable dosages and their efficient and rapid transport to the infection site. Indiscriminate or inappropriate use can encourage the development of resistance in fungi. The high level of efficacy of five fungicides in our study (Metalaxyl, Fluopicolide, Mandipropamid, Propamocarb and dimethomorph), might help in alternating the use of fungicidal treatments to prevent development of fungicide resistance. Evaluation of MICs of ten fungicides helped to standardize the doses of fungicides against P. nicotianae along with traditionally used Ridomil gold in the present study. This study will be much helpful in future to devise fungicidal application schedule for commercial orchards.

References

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How to cite this article

Sanhita Malvi, Jayant Bhatt, Ashis K. Das, Pratik Pali, Ashok Kumar, Aatmika Chouhan and Sanjay Kharte (2022). Evaluation and Determination of Minimum Inhibitory Concentration of fungicides against Root Rot Pathogen of Citrus (Phytophthora nicotianae). Biological Forum – An International Journal, 14(4): 415-423.