Vol. 11, Issue 6 (2022)

Author(s):
Shah HM, Jaiman RK, Patel JR and Jani MD

Abstract:
Leaf blight caused by Phytophthora colocasiae Raciborski is the most important disease of colocasia and has become a limiting factor for production in all colocasia growing areas in India. The results revealed that all the seven bioagentstested in vitro applying dual cluture technique against Phytophthora colocasiae significantly inhibited the mycelial growth of the test pathogen over untreated control. Howerver, T. harzianum (Sardarkrushinagar) highest inhibition (69.99) of mycelial growth of Phytophthora colocasiae over control followed by T. harzianum (Junagadh) with 69.25 per cent inhibition. Results revealed that different fungicides tested in vitro applying Poisoned Food Technique against Phytophthora colocasiae significantly inhibited the mycelial growth of the test pathogen over untreated control. Among systemic fungicide more than 90% growth inhibition was recorded in azoxystrobin, difenconazole and propiconazole (99.25, 98.14 and 97.77%, respectively) at 500 ppm concentration. The next best in order of merit was Azoxystrobin at 250 ppm concentration with 97.77% growth inhibition. Among non-systemic fungicides more than 90% growth inhibition was recorded in mancozeb, copperoxychloride and chlorothalonil (96.66, 90.73 and 90.73%, respectively) at 2000 ppm concentration. The next best in order of merit was mancozeb at 1500 ppm concentration with 92.22% growth inhibition. Compound fungicides in general revealed that metalaxyl 8% + mancozeb 64% WP recorded significantly highest growth inhibition of 100 and 99.25% at 500 and 250 ppm, respectively followed by carbendazim 12% + mancozeb 63% WP with 98.51% growth inhibition at 500 ppm. Evaluation of different botanicals by Poisoned Food Technique showed that all plant extracts tested in vitro were found significantly effective in reducing the per centage mycelial growth of Phytophthora colocasiae over control. Effective mean growth inhibition percentages of 51.84, 47.77, 43.69, 43.14 and 43.14 was recorded in aqueous extracts of neem leaf, lantana, NSKE, ardusa and barmasi. Four de oiled cakes at 5, 10, 20 and 30 per cent were tested for its efficacy against the radial growth of P. colocasiae using poisoned food technique. More than 85% growth inhibition was recorded in neem cake and castor cake (93.33 and 88.51%, respectively) at 30 per cent concentration.