artifact on my grass only with path tracing Movie render queue

hi everyone,
sorry for my bad english.
i don’t know unreal good, i’m new user.

i created a forest with grass, when i use pathtracing in Movie render queue, even if i use antialiasing 32 x32 or 64 x 64, i have always artifact on my grass.
i upscaled my light resolution, but nothing better.

Is there a specificity for improve this?

thank you for your help.

Best regards.