Efficacy of Mancozeb and Ocimum gratissimum Extract in the Management of Late Blight Disease in Tomato Varieties

Abstract

Tomato late blight is an economic disease that causes 100 % yield loss of tomato in Cameroon. The objective of the study was to determine the efficacy of mancozeb and Ocimum gratissimum extract in managing late blight disease in Nadira and Rio-grande tomato varieties. Seedlings of each tomato variety were planted in replicates of three in a complete randomized block design comprising of three treatments (T1 –Ocimum gratissimum extract (1666.7 g/15 L); T2 –Mancozeb (50 g/15 L); T3 –control. Fifty grams of mancozeb (50g) and 1666.7 g of O. gratissimum extract dissolved and mixed with water in a 15 L knapsack sprayer was applied to control tomato late blight from the onset of blight symptoms, at two days intervals, to control Data for the disease incidence, severity, and yield parameters were collected at weekly intervals for four weeks from plants in the middle of the ridges.  Mancozeb and O. gratissimum extract significantly reduced the disease severity of  Nadira and Rio-grande tomato varieties by 0.2., resulting in a mean fruit number of 18.31 and 16.31 fruits and fruit weight of 1.44 g and 1.13 g. There was no significant difference (p =0.05) between plants sprayed with Mancozeb and O. gratissimum extract. The Nadira variety was resistant to the tomato late blight caused by Phytophthora infestans. Thus biopesticides (O. gratissimum) can be effectively used as alternatives to synthetic fungicides (mancozeb) –which pose risks to human and environmental health.