Random, I see pearl white, healthy larva. As HP suggest the flora source may be the culprit. On the other side of the planet, I have no idea about your Fall foliage. Our Fall produces golden rod that is somewhat unpleasant smell to me.
Some known:
Bacteria have a putrid smell, very offensive, nauseous. the smell is Putridizen[sp] very poisonous.
Yeast have bitter smell offensive, unpleasant but not nauseous to most.
Regarding the beetles add to your arsenal, freeze spray, nontoxic, nonflammable used to freeze skin aberrations by MD and also by chip mfg to blow off dust. The spray is minus 62F at the tip so be careful not to freeze your skin. Available at office supply or amazon.
Cheers