Chop Wood Carry Water Plant Seeds is a blog about Self-Sufficient Homesteading. How can we live by creating a sustainable bio-diverse world, instead of by consuming and destroying the only one we have? What kind of teaching have you got if you exclude nature?

Saturday, January 19, 2013

The Nematode Killing Fungus can Save our Vegetable Garden

How the fungi do their work

The fungi destroy nematodes in a number of ways. In some cases the fine threads of the fungus have branches which form loops and these loops in turn form three-dimensional networks, something like crumpled wire netting. This network secretes a sticky fluid when they come into contact with the nematodes and the nematode is caught as effectively as a fly in a spider web. After the fungus catches the nematode it then sends branches into its body or grows into it and simply absorbs its tissue.

Another way in which fungus traps nematodes is by sticky branches which reproduce rapidly and form little circular loops in which the nematode is trapped.

The third way the fungi works consists of sticky knots at the end of stalks. These knots hold the nematode and form a structure inside which spreads out and destroys it.

The fourth way is by the formation of a constricting ring of three cells on a stalk. The nematode gets its "nose in a noose" or ring accidentally; the cell swells and the ring closes.

Predatory nematophagus fungi

Over 200 species of fungi use specialized structures to capture free-living nematodes. They produce traps at intervals along the length of their hyphae that capture, penetrate, kill and digest a nematode’s contents. 

 Scanning electron microscopy (Magnification=560x) of nematode-trapping loops of fungi imperfecti (Arthrobotrys oligospora), nematophagous fungi. Close-up of hyphae with adhesive matrix.

Scanning electron microscopy of the carnivorous fungus Arthrobotrys anchonia capturing a nematode.
Fungi can capture nematodes in a variety of ways but the most sophisticated and perhaps the most dramatic is called the constricting ring. An erect branch from a hypha curves round and fuses with itself to form a three-celled ring about 20-30 microns in diameter (30/1000th mm). When a nematode "swims" into a ring it triggers a response in the fungus and the three cells expand rapidly inwards with such power that they constrict the body of the nematode victim and hold it securely with no chance to escape. It takes only 1/10 th of a second for the ring cells to inflate to their maximum size.

Fungi Nutrition

Predatory fungi have evolved these trapping devices to
obtain nutrients and give them an edge over other types of
organisms in habitats where population densities are high
and consequently competition for resources is fierce.
The primary function of predatory fungi is wood decay.
Wood is mainly composed of carbohydrates: cellulose and
lignocellulose. The carbon to nitrogen ratio (C:N) of wood
is very high at 300:1–1,000:1 or even higher. For good
growth to occur, most organisms require a C:N ratio of
30:1 to produce nucleic acids, proteins and enzymes. For
predatory fungi nitrogen is the limiting factor for growth.
Nematophagus predatory fungi get their extra nitrogen from
digesting the nematode’s biomass.
This means that predatory fungi are not true saprotrophs
(which live on dead organic matter) as two phases that run
in parallel are necessary to supply them with the correct
nutrients for growth – the predatory parasitic phase and the
saprotrophic phase. Predatory fungi are facultative parasites.

 Wood Chip gardening as the perfect environment for various fungi and microbes.

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