Mechanical Vs Biological.

But things didn't end there. The elves retaliated soon after by ramping up the production of mutated fungi spores, which they directed towards the camp of the humans.

These spores were either deadly if inhaled or could quickly germinate into something deadly if given soil to grow. It just so happened that soil is the one thing that the Lignum world is not lacking. 

The poisonous spores didn't work because the soldiers had their armor, which could create an air pocket of filtered air around them.

The fungi also couldn't grow because the soil had been sprayed with herbicides and other toxic chemicals designed to kill and inhibit plant growth. 

But things became a little strenuous when the elves managed to raise another batch of giant worms and put them to work creating acid rain over the camp of the humans.