I got a i5-3750 k 3.40 ghz and 8g assigned to minecraft + 570 ti and i cant continued my wolrd of survival because i got drop of 80 to 0 fps in times of 1 to 3 seconds on biome of jungle. PD i start this world in the snapshot 14w08a

From MC-51140:

Frame rate drops to 1 FPS in jungle biomes. This does NOT appear in any official released versions.

Possible cause: I found that the leaf block's are now killing mobs that spawn in them. Causing tons of dropped items causing lag.