I recently ran across an article I saved a few years ago entitled, "Fungi slay insects and feed host plants" that you might also find interesting. It describes experiments by researchers at the University of Guelph in Ontario, Canada, who were studying the feeding habits of springtails (tiny soil bugs) which normally eat fungi. The researchers were wondering if the insects were having a negative effect on the environment by eating certain species of fungi and indirectly starving plants (such as pines) that depend on mycorrhizal fungi to help them get their nutrients.
They fed various types of fungi to groups of springtails to see which ones the springtails preferred. To their surprise, when the ectomycorrhizal fungi Laccaria bicolor was served, almost all the springtails died. The researchers likened this to seeing a pizza eating a human - it was the complete reverse of what they expected.
Further analysis found that the fungus first paralyzed the springtails, quite likely with a toxin, then extended nutrient-seeking filaments into the insects, in effect taking the nutrients from the springtails' bodies to their host plants.
To confirm their chance findings, the researchers treated roughly 500 springtails to a helping of L. bicolor. After two weeks, only five percent of the springtails remained alive. In contrast, all the insects that were fed different species of fungi or whose diet was devoid of fungi survived.
Then, to see how much of a plant's nitrogen might come from insects, the scientists radioactively labeled nitrogen atoms in the insects' bodies and followed their trails in eastern white pine seedlings. They found that after two months, 25 percent of the plant's nitrogen had come from the insects. "That's very significant," said a molecular biologist at Michigan Technical University. "It's almost like the plant is actively seeking nitrogen from the insects and getting it through the fungus."
My only quibble with the last comment is that the biologist credits the plant and not the fungi for developing this insective feeding strategy. More and more, I believe that it is fungi that control much of the underground world - orchestrating host plant feeding/protection by foraging throughout the surrounding soil and even attacking plant predators if that opportunity presents itself.
To support this idea, there are microscopic photos from other researchers showing fungi trapping nematodes in hyphae loops to immobilize and kill them. And yet another study reported that the fungus Glomus mosseae (one of the types in our inoculant products) reduced nematode damage in clover roots by 70%. Add in other research with radioactive tracking that documents how mycorrhizal fungi routinely transport nutrients from adult trees to nearby seedlings, and a picture of an interlinked fungus-based feeding system emerges. This elegant system apparently obtains plant nutrients from a variety of sources; bacteria, earthworm castings, soil fauna, neighboring plants, soil minerals - wherever.
A plant that has the good fortune to have the right types of mycorrhizal fungi colonizing its roots has it made as far as food and root protection issues are concerned. Its success is pretty much guaranteed, being plugged into a very efficient plant-tending network. In time, I'm sure we humans will better learn how to utilize these sort of biosystems to grow our food crops and ornamental plants. I doubt that chemisty alone has all the answers for the long haul.
A couple key points: Not all fungi species have developed this insect-devouring behavior. Further research could help pin down (fairly quickly, I would think) specific fungus types that might be most useful for specific plant protection. Also, it remains to be seen if critters other than microscopic springtails and nematodes can be fungi-controlled. For example, is there a type of fungus that would make nourishing meals out of phylloxera, a soil louse that attacks grapevine roots, or is that pest too large? Maybe we need put the word out to researchers that we're looking for a Tony Soprano type fungus for vineyard duty.
Cheers, my friends,