Management of Phytophthora Leaf Fall Disease of Nutmeg (myristica Fragrans Houtt.)

Nutmeg trees are proned to various fungal diseases. Recently, a leaf fall disease caused by Phytophthora sp. has become a serious problem in Kerala, during South - West monsoon period resulting in poor crop stand and yield. In vitro and in vivo studies were conducted to find out the efficacy of different fungicides and bioagents against this pathogen. In vitro evaluation of different fungicides showed, complete inhibition of the pathogen with 1% Bordeaux mixture, copper hydroxide (2 g l-1), copper oxychloride (2.5 g l-1), potassium phosphonate (3ml l-1) and the combination fungicides iprovalicarb + propineb (1.5 and 2.0 g l-1) and cymoxanil + mancozeb (2 g l-1) and the antagonists viz. Trichoderma viride -1, T. harzianum and T. viride -2, the isolates from nutmeg rhizosphere soil and the reference cultures, T. viride (KAU), T. harzianum (IISR). Of the various treatments tested in in vivo experiment, spraying of 1% Bordeaux mixture + soil drenching of copper hydroxide (2 g l-1) and spraying of 1% Bordeaux mixture + soil application of T. viride showed maximum reduction of the disease. All copper fungicides tested under study were effective, of which, Bordeaux mixture was the most promising one followed by copper hydroxide and copper oxychloride. In addition, either spraying or drenching with systemic fungicides viz. iprovalicarb + propineb and cymoxanil + mancozeb also showed good results. Soil application of Trichoderma alone was found to be effective however, prophylactic spraying of 2% Psuedomonas fluorescens and soil application of Trichoderma showed better result.