If a player right clicks a fully grown cotton plant from pam’s harvest craft it will cause a crash. I also noticed there are 2 different types of cotton plant one called “cotton” this is the one that you get when you plant the seeds and “cotton seeds” these can only be found in green houses and do not have the crash issues. (I found the names of the plants with waila)
Relevant mods to the crash and versions:
AgriCraft-1.7.10-1.4.0-alpha-4-1.7.10
Pam’s harvest craft 1.7.10i
Forge10.13.4.1448-1.7.10
Crash log: http://pastebin.com/AcfdEYQG

I'll have a look at it this evening, thanks for the report.

I managed to replicate the issue. Cotton itself is instance of ItemSeeds as well, don't ask me why, but it is. I've added an exception to ignore it while scanning for harvestcraft seeds.