Congestion plays an important role in degrading the performance of the Wireless Sensor Networks (WSNs). When an event is not detected, the network load is very low whereas when an event is detected the network load becomes high which leads to congestion. Due to congestion the overall performance of the network degrades. Hence it is necessary to detect and control congestion. In this paper an efficient technique to detect and control congestion has been proposed. The congestion is detected by calculating a metric called Congestion Degree (Cd). It is the ratio between packet inter arrival time and packet inter service time. Once the congestion is detected the congestion notification signal is sent to all intermediate nodes by using the Implicit Congestion Notification (ICN) signalling. The congestion is controlled by implementing Fuzzy Logic Controller. The performance of the network is measured for different transmission rates and number of active sources.