There is increasing evidence that biochar in the soil can lead to dramatic reductions and even complete elimination of root-eating nematodes, the bane of organic growers who cannot use nematicidal organophosphate pesticides to kill them before they eat away at the roots of their plants. Many of these nematicides are now prohibited in the EU because of human health concerns – Bayer announced the discontinuation of their Aldicarb product in 2014.
What we do know is that fungi can trap and eat harmful nematodes. We also know that in healthy organic soils the addition of biochar can increase fungal populations from 1 billion per handful of soil to 1 trillion. Faced with such a formidable army of fungi, most nematodes stay well away and soil tests by Carbon Gold customers who use biochar on tomatoes and on turf have shown that root-eating nematode levels become insignificant.
This is probably because biochar particles are like a 5 star hotel for fungi, giving them a refuge from predators that prey on them, while enabling them to maintain the high population level that prevents nematodes and undesirable fungal diseases from getting near to the plants with which they have a symbiotic relationship.