by Greg Doering, Foodweb Online, L.L.C.


What comes to mind when soil fungi are mentioned? For many growers the devastation from fungal pathogens such as Phytophthora, Pythium, Rhizoctonia, or Verticillium that attack roots paint a bleak picture. True these fungi are a nurseryman's worst nightmare, but there are other pathogen or parasite type fungi that actually can be used in a positive way by controlling diseases. Nematode-trapping fungi can parasitize disease-causing nematodes. Also insect-feeding fungi can be useful as a biocontrol agent.

Soil fungi make up one of the most important and largest populations in a healthy, complex soil food web. The second group of fungi are the decomposers or saprophytic which obtain their energy by converting dead organic matter into fungal biomass, CO2, and organic acids. They break down the cellulose and lignin in wood. Like bacteria, they immobilize and retain nutrients, create new organic compounds that are sources of energy & nutrients, produce compounds & hyphae that help bind soil into aggregates, and compete with or inhibit disease-causing organisms.

The third and most talked about group of soil fungi are the mutualists or mycorrhizal fungi that colonize plant roots. These beneficial organisms enhance plant growth by helping solubolize phosphorus and bringing nitrogen, phosphorus, trace minerals, and even water to the host plant. A second very important function is their ability to protect roots from disease-causing organisms.

Over 95% of cultivated and natural growing land plants form symbiotic relationships with mycorrhizal fungi. From this statistic, it would seem logical that a progressive grower should know what his soil contains and if their mycorrhizal populations are adequate. Natural, undisturbed, high organic woodlands contain high populations of beneficial fungi. Unfortunately, research indicates that common practices have destroyed or greatly limited the potential for high mycorrhizal populations. Among these practices that can contribute or create problems include: tillage, removal of topsoil & organic matter, erosion, soil compaction, overly saturated soils, pesticide applications, fumigation, and salt build up from commercial fertilizers.

Next lets look into the different type of mycorrhizal fungi. Fungi that colonize the outside of the roots are call ctomycorrhizae. They occur on about 2000 species of woody plants. Trees that fall into this category include the following families: Pinaceae, Fagaceae, Betulaceae, Salicaceae, Juglandaceae, Myrtaceae, and Ericaceae. They occur only on woody plants and most generally are recognized with an unaided eye. There are over 5,000 species of these fungi. Many produce mushrooms or puffballs.

Endomycorrhizae are the most widely spread type of mycorrhizae of which there are three main types. Ericaceous occur on some families in the Ericales and include rhododendron, azalea, laurel, cranberry, & blueberry. Orchidaceous are another distinct type that only associate with the Orchidaceae family. Unfortunately, to my knowledge neither one of these types of endomycorrhizae is commercially available at this time, but their populations can be increased with select FWOL products.

Over 1,000 genera of plants representing over 200 families and nearly 300,000 species have a symbiotic relationship with vesicular-arbuscular mycorrhizae (VAM). There are currently about 150 species of VAM fungi currently identified. They are microscopic and cannot be grown in pure culture on artificial media in the laboratory. Therefore they must be harvested from natural areas. Most ornamentals from desert to woods, fruit & nut trees, vines, flowers, grasses, and agricultural crops rely on the benefits of these small fungi. VAM populations are important to most nurseries!

When VAM populations are healthy, there will be increased plant efficiency & health, resistance to insect & disease, improved fertilizer utilization, drought resistance, greater quality & production, and fewer days to harvest. Should you test your soil or growing media? You be the judge.

The key for success is a balance and proper mineral & soil qualities along with biological diversity. Fortunately there are various cocktail endo & ecto mycorrhizal formulations available. We have found the Plant Success products to be some of the most cost effective mycorrhizal products for large growers. Not only do they contain mycorrhiza, but also rhizopogon, plus humic acid, seaweed extract and other root biostimulants. Coupled with soil foodweb activator products like Lase, Blend, & Mycorrcin that increase beneficial bacteria and fungi, mycorrhizae populations can be managed to increase your crops potential.

Under dry conditions fungi can bridge gaps between pockets of moisture ad continue to survive and grow when bacteria have ceased to be active. They also are able to use nitrogen from the soil allowing them to decompose surface residue, which is often low in nitrogen. Quit giving fungi the bum rap. Start using them to your advantage. Ask your nursery consultant GINA how to get started.


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