The experiment field was protected by a metal net, and there was an automatic water-spraying system underneath the net and above the field, this system sprayed mist- like water for 30 seconds per hour from 10 o’clock in the morning to 4 o’clock in the afternoon to increase humidity in the atmosphere during the infection period from artifi- cial inoculation of rice plants with U. virens to emer-
gence of the smut balls on rice panicles.