Cajanus cajan (Pigeon pea) is economically an important crop which provides high quality vegetable protein and high nutritional value. But different biotic and abiotic factors like weather, temperature, insect pests and different diseases constraint the potential yield of crop. In view of little information on diversity of insect pest and their infestation on various growth phases of this crop under varied climatic condition of this region, survey was conducted in different areas i.e., Telpa, Rouja and Katra of chapra. A total of 3 fields were surveyed weekly from Oct to March 2015-2016. The insect pests found are Helicoverpa armigera Pod-fly, Plume moth and Cow bugs, Thrips, Blister beetles, Blue butterfly of order Coleopteran, Dipterans, Hemiptera and Homoptera including diseases like cercospora leaf spot, fusarium wilt, and sterility mosaic. H.armigera was found to be major pest with its predominant presence in all sites surveyed.