The population of green spider mite Mononychellus tanajoa (Bondar) was monitored on cassava for 52 weeks (mid October 1979 to mid October 1980) at Moor Plantation, Ibadan, Nigeria. Mite population was found to be high in the dry season (80.1 ± 57.7 per leaf) and low in the wet season (15.2 ± 13.5). There was a linear relationship between mite population and the weather factors investigated. The relationship was positive in the cases of temperature and radiation, and negative in those of rainfall and humidity. The high mite population in the dry season was attributed to the high temperature (27.9 ± 1.26°C) and radiation (39.1 ± 7.86) conditions which favoured development of the different stages in the life cycle of the mite. The low population in the wet season was attributed to the adverse effects of high rainfall (56.31 ± 33.14 mm) and humidity (87.29 ± 2.36%) on the mites. Seasonal fluctuations in mite population was attributed to the physiological condition of the host plant.
