Effects of Temperature and Relative Humidity on the Germination and in vivo Infection Dynamics of Sphaerotheca fuliginea fungus on Watermelon (Citrullus lanatus) in Sokoto, Nigeria

Powdery mildew (PM) caused by (Sphaerothe cafuliginea fungus) is a major foliar disease affecting greenhouse and field-grown watermelons worldwide. Infection at an early stage of watermelon plant by S. fuliginea reduces seedling and vigor causing premature desiccation of leaves. This research investigates the effects of temperature and relative humidity on the conidial germination and in vivo infection of Sphaerotheca fuliginea on healthy watermelon plants. The experiment was laid out on Completely Randomized Design (CRD) in the laboratory with (5) replications in each case. Conidia of Sphaerotheca fuliginea was subjected to different temperatures and relative humidity of (30, 35, 40, 45 oC and 52%, 63%, 86%, and 94%, respectively) for conidial germination, mycelium length, width, and in vivo infection. Results showed that lower temperature ranges (30 °C-35 oC) and higher relative humidity (>70%) often enhance the conidial germination of Sphaerotheca fuliginea and in vivo infection, research revealed how Powdery Mildew be triggered by lower temperature of 30 OC and high relative humidity of ~94% in watermelon (Citrullus lanatus) in Shagari Local Government Area of Sokoto State. Based on the result obtained, the best time for Watermelon cuttivation around Shagari Local Government Area should be from February to May, in which temperature and relative humidity levels are not favourable for developing Powdery Mildew.