Effect of Climate Change on the Management of Phytophtora Pod rot of Cacao in Nigeria

Cocoa production is an important economic activity in growing ecologies of Nigeria. Theobroma cacao is prone to diseases, among which pod rot caused by Phytophthora species is major with economic crop losses if not managed. Hence, an effective crop protection strategy is major in cacao production and application of copper – based fungicides is a regular practice by farmers. But the advent of climate related challenges on the efficacy of fungicides against Phytophthora pod rot of cacao is a major concern. Field trials were conducted in 2014, 2015 and 2016 at Onigambari; Lat. 7.216oN, Long. 3.852oE by application of copper-1-oxide 60% + metalaxyl 12% WP between May and October each year. Three spray regimes (fortnight monthly-spray, monthly-spray and no spray application) were adopted. The regression analysis of weather parameters (relative humidity, temperature and rainfall) with black pod disease incidence indicate strong relationship and high R-square value. Weather significantly affect the black pod incidence: positive correlation between black pod incidence and relative humidity (r= 0.19, 0.53) except in year 2016 which recorded a negative linear correlation (r= -0.19). Negative correlation (r= -0.54) was recorded between black pod incidence and temperature in year 2014 and 2015 but positive (r=0.53) in 2016. The linear relationship between black pod disease and rainfall showed a negative correlation (r=-0.42). Effect of weather was established both in temporal and spatial distribution of pod rot incidence in cocoa production and environmental factors influencing development of Phytophthora pod rot were both positively and negatively correlated. 

Keywords: Cacao, Phytophthora pod rot, fungicide application, timing, climate change