Seasonal and diurnal changes of two leaf pathogens of Rubber (Hevea brasiliensis Muell. Arg.) in the air of Iyanomo, Nigeria

Abstract

Air spore concentrations of Drechslera hevea Petch and Colletotrichum gloesporoides Penz were studied in a rubber nursery, over a 12-months period, from March 1976 to February 1977, using both the exposed nutrient medium technique and Rotorod samplers. Both methods showed seasonal changes in the spore concentrations of these organisms throughout the year. The spore concentrations of D. hevea were consistently higher than those of C. gloeosporoides. The highest spore concentrations were recorded in February and August for D. hevea and C. gloeosporoides respectively. In both cases there were diurnal fluctuations, with peaks occurring between 12.00h and 14.00h. The effect of environmental factors on these changes in discussed.