Management of Phytophthora nicotianae, the incitant of citrus foot rot, with new generation fungicides

Foot rot caused by Phytophthora nicotianae is a serious disease in citrus nurseries and orchards. For its management, bio-efficacy of total nine fungicides (five systemic and combination, two systemic and two contact fungicides) was evaluated in vitro and under pot house conditions against citrus foot rot at Punjab Agricultural University, Ludhiana. Fluopicolide 4.44%+propamocarb hydrochloride 66.67%WG and metalaxyl 4%+mancozeb 64%WP effectively controlled the mycelial growth with ED50 value of 0.8μg/ml followed by cymoxanil 8%+mancozeb 64%WP (ED50 value 18.0μg/ml), while chlorothalonil 75%WP was the least effective in inhibiting mycelial growth of the pathogen (ED50 value 328.0μg/ml). Under field conditions, metalaxyl 4%+mancozeb 64%WP was the most effective in controlling the pathogen population and increasing shoot and root length, seedling canopy, leaf area, number of rootlets, root volume and density of Rough lemon seedlings as compared to fluopicolide 4.44%+propamocarb hydrochloride 66.67%WG and cymoxanil 8%+mancozeb 64%WP. Seedlings treated with fosetyl aluminium 80%WP had significantly lesser shoot and root growth. All the treatments had root rot rating of 1 as compared to 4 in untreated check.