generally insects are attracted by the light. During night time keep a light source in the field. Below the light source keep a tray filled with water, to that add some castor oil, Aloe vera or kerosene. Keep this set up from evening 6 pm – 8pm. This light source attracts the harmful insects and when they come near they fall into the water tray and die. This light trap should not be kept after 8 pm because many beneficial insects comes only around this time.