In case the bright spots are caused by sun being reflected by the grass blades, this is a physically correct phenomenon that you can also observe in real life (examples: waves on the water reflecting sun, "sparkling" snow).
Examples
Example of bright pixels visible in grass:
glossiness = 1.0To mitigate this effect, you can:
1. Lower glossiness value of the grass material:
Glossiness lowered from 1.0 to 0.5 in 3ds Max and Cinema 4D:
After lowering material's glossiness to 0.5, sun reflections became "softer" and more realistic:
2. Disable reflection visibility for Corona Sun in 3ds Max and Cinema 4D:
Result of disabling sun's reflection visibility:
There are no bright pixels but the grass looks less realistic. Using this option will globally disable sun reflections for all objects.
Other solutions
You can use Highlight Clamping (3ds Max | C4D) to clamp the brightest parts of the image and thus get rid of fireflies and noise.Another solution is using the Fireflies Filter (3ds Max | C4D).