Mycorrhizae FAQs

Usage and Application Questions

What are Mycorrhizal Fungi, or Mycorrhizae?

“Myco” – “rhizal” literally means “fungus” – “root” and describes the mutually beneficial relationship between plants’ root systems and these beneficial fungi. These specialized fungi colonize plant roots and extend far into the soil to acquire resources that plants can’t access alone, beyond the nutrient depletion zone, and in forms that are tightly bound and not available to the plant. Mycorrhizal fungal filaments (known as “hyphae,” and collectively as “mycelium”) in the soil are truly living extensions of plants’ root systems and are more effective in nutrient and water absorption than the roots themselves. This symbiotic relationship dates back several hundred million years, and approximately 95% of the planet’s terrestrial plant species rely on this mycorrhizal symbiosis to thrive.

How do Mycorrhizae Help Plants?

Mycorrhizae form a symbiotic relationship with the plant roots. The hyphae, or fungal roots, can grow faster and longer than plant roots can grow, and can expand beyond the nutrient depletion zone of the roots themselves. Through the mycorrhizal colonization and hyphal network growth, the effective surface area of the plant’s root-and-mycelial network is expanded, allowing for increased access to micronutrients, macronutrients, and water for the plant. This results in many benefits to the plant, including increased vigor, drought resistance, stress resilience, transplant success*, and optimized fruiting/flowering.
*A study conducted at the University of Guelph concluded that plants with mycorrhizae have double the transplant success of untreated plants.

What are the Different Types of Mycorrhizae?

There are two different types of mycorrhizal fungi that are utilized in the products offered by Mycorrhizal Applications: Endomycorrhizae and Ectomycorrhizae.  Endomycorrhizae form relationships with approximately 85% of plant species, including most commercially produced plants.  Ectomycorrhizae form relationships with approximately 10% of plant species, including many conifers and hardwoods.  Some plant families, such as the Orchidaceae and Ericaceae, require very specific types of mycorrhizae and will likely not respond to the mycorrhizal products offered by Mycorrhizal Applications.

What is the Difference Between Endo and Ecto Mycorrhizae?

Endomycorrhizal Fungi form resource exchange mechanisms on the inside of the plant’s root cells, intracellularly (and the hyphae extend outside the root). Endomycorrhizal fungi form mostly with green leafy plants and most commercially produced plants. Examples: Most Vegetables, Grasses, Flowers, Shrubs, Fruit Trees, and Ornamentals. Approximately 85% of terrestrial plant species on Earth are endomycorrhizal.

Ectomycorrhizal Fungi form exchange mechanisms outside of the root cells, extracellularly. Ectomycorrhizal fungi form mainly with Conifer and Hardwood species and are required mostly for woody plants/trees and forest trees. Approximately 10% of terrestrial plant species on Earth are ectomycorrhizal.

What Plants Form Symbiotic Relationships with Mycorrhizal Fungi?

Approximately 95% of the world’s terrestrial plant species form mycorrhizal relationships and require this symbiosis for maximum performance.

  • You can use our searchable database of plant/mycorrhizal relationships to determine whether your crops are mycorrhizal, and which type of mycorrhizal fungi they will partner with CLICK HERE

How do Mycorrhizal Fungi Increase Nutrient Uptake?

Mycorrhizal fungi act as living extensions of the plant’s root system, effectively increasing the surface absorbing area, thereby greatly improving the ability of plants to utilize soil resources such as nutrients and water. Roots are limited to their root tips for nutrient cation exchange; however, mycorrhizal hyphae can absorb nutrients all along the lengths of the filaments. The diameter of mycorrhizal hyphae is also much smaller than roots (in fact endomycorrhizal hyphae are completely microscopic) and are able to access areas of the soil that roots can’t access. Not only do mycorrhizal fungi increase nutrient uptake by increasing the effective surface absorbing area of the root system, but they also release powerful enzymes into the soil that can help to solubilize tightly bound soil nutrients.

This mycorrhizal benefit is particularly important in the plant rhizosphere (root zone ecosystem), and many of the main grower benefits of mycorrhizal inoculation come from this nutrient uptake increase. These benefits include reduced nutrient run-off, better plant performance in marginalized soils, more efficient plant uptake of applied fertilizers and nutrients, a reduction in the need for fertilizers in some situations, and much more.

What Other Benefits do Mycorrhizal Fungi Provide?

Mycorrhizal fungi are involved with a wide variety of other activities that benefit plant establishment and growth. The same extensive network of fungal filaments important to nutrient uptake is also important in water uptake and storage. In trials on a multitude of plant species growing in many various conditions, mycorrhizal plants are far less susceptible to drought stress when compared to non-mycorrhizal plants.

Mycorrhizal fungi also improve soil structure. Mycorrhizal filaments (hyphae) produce organic “glues” (extracellular polysaccharides and glycoproteins, such as Glomalin) that bind soils into aggregates and overall improve soil structure and porosity. Soil porosity and soil structure positively influence the growth of plants by promoting aeration, water movement into soil, root growth, and distribution.

The mycorrhizal symbiosis and the subsequent plant benefits and increased resiliency also help to decrease transplant shock and increase transplant success. A study conducted at the University of Guelph concluded that plants with mycorrhizal networks have double the transplant success of untreated plants.

How Can I Conduct a Growing Trial With Mycorrhizal Fungi?

We have developed a Trial Protocol for professional growers to learn the basics of setting up a mycorrhizal trial, which includes guidelines for Trial Analysis and Conclusions.

Mycorrhizal Trial & Analysis Protocol: CLICK HERE

If you are interested in conducting a trial within your professional growing operation, please feel free to contact our sales team: or (866) 467-7800

Do Mycorrhizae Control Plant Disease?

Mycorrhizal fungi do not have pesticidal or disease-suppressing benefits.

Are Mycorrhizal Fungi Present in Compost?

Mycorrhizal fungi are not naturally present in compost, as they are obligate symbionts that rely on a living plant host to survive. The heat generated through the composting process can be detrimental to mycorrhizal propagules as well, so we recommend adding mycorrhizae at the end of the composting process, before adding to soil or growing media.

What if Too Much Mycorrhizae is Applied?

There are no negative effects from overdosing plants or soil with mycorrhizal inoculum. The same is true for applying the wrong type of mycorrhizae (e.g. applying ectomycorrhizae to an endomycorrhizal plant), as the mycorrhizae will remain dormant in the soil and will have no negative effect on the plant or rhizosphere.

How do You Apply these Mycorrhizal Fungi?

The MycoApply product line has been developed to offer the most versatile, diverse, and efficient application options possible. Effective mycorrhizal inoculation can be achieved in a number of ways. The goal is to create physical contact between the mycorrhizal inoculant and the plant root. MycoApply products can be incorporated into the soil or growing media, applied directly to roots during transplanting, applied in-furrow, drenched or “watered in” via irrigation, sprayed or “sprenched”, applied as a root dip or plug dip, injected into the root zone of existing plants, coated onto seeds, or any method that gets the active ingredients in close contact with growing or emerging roots where the colonization can begin. The type of application depends upon the conditions and needs of the applicator, so growers can choose the application method that best fits into their current growing practices and protocols.

What is the Best Application Timing?

While plants can be treated at any time during their life cycle, we recommend that mycorrhizae are applied as early as possible in the plant’s growth.  Applying at seeding, propagation, or transplanting gets your plants off to their best start and maximizes the potential for impact by the mycorrhizae.  This timing is also the most cost-effective since a lower volume of soil will be treated, requiring less MycoApply product per plant than application in later stages would require.

What Tips Should I Keep in Mind When Applying Mycorrhizae?

1. The main goal of any mycorrhizal application is to get the product in contact with the growing roots of the plants being inoculated. Since the mycorrhizae germinate in the presence of root exudates, this is the key to successful inoculation. We have formulated our products in many different forms (granular, suspendable powders, concentrated powders, non-aqueous liquid suspensions, etc) to ensure that growers have multiple application options. You know your equipment and application needs the best. We are here to help if you have questions.

2.  Mycorrhizae are hardier than you might think, which has helped them to survive the last 450 million years. There are some conditions to avoid:

  • High temperatures of 140 degrees F and above can reduce the viability of the mycorrhizal propagules.
  • Not all, but certain Fungicides can be detrimental to the viability of mycorrhizal fungi. Please see our List of Fungicides and their know effects, to help you pick a mycorrhizae-friendly fungicide. (For Agricultural fungicide interactions with mycorrhizal fungi, please consult with your crop adviser or contact the Valent BioSciences Biostimulant Unit.)
  • Mycorrhizal fungi actually attach and become part of the plant, they are not free-living soil organisms, they require that symbiotic relationship, meaning they will stay with the plant for the life cycle of that plant. When annual plants die, or a field is tilled, etc those mycorrhizae do not remain indefinitely, and the hyphal mycorrhizal networks die along with those plants.

3.  High levels of available Phosphorous do not harm or kill mycorrhizae, but they can slow the colonization process. One of the main functions of mycorrhizae is to solubilize and extract phosphorous. However, if there is already an overabundance of phosphorous available to the plant, the plant is less likely to trigger the germination of the mycorrhizal propagules and establish the symbiosis. This means they won’t be performing some of their other important tasks like water uptake, and other nutrient extraction as well. Therefore, we recommend keeping available phosphorous at a low to moderate level. This is most important at the time of inoculation when the mycorrhizal propagules are awaiting the chemical signal from the plant in order to attach to the plant and initiate the symbiotic colonization of the plant’s root system.

When will I Start to See a Difference After Applying Mycorrhizae?

The mycorrhizae go to work immediately after application to a growing plant root and will take about 4 weeks to establish the symbiotic relationship. Though it varies by plant species, growing protocol, etc., it generally takes about 8 weeks for benefits to become visible to the grower in comparison trials. Differences may be visible sooner in more stressful growing conditions, as this is when the mycorrhizae can bring the most benefits to the plants. If plugs or liners have been treated, differences in performance may be more noticeable when they are transplanted into a larger container.

How Many Applications are Required?

Mycorrhizae remain in a symbiotic relationship with the plant for the entire plant’s life. When a plant is transplanted into a landscape, the mycorrhizae join the soil ecosystem and change as it changes. Most annual plants only require one application. Reapplications can be done to ensure continued maximum impact for longer-term perennial plants. If a treated plant goes through a bare-root phase, the plant will need to be retreated once it is planted again. Contact your Mycorrhizal Applications sales representative to discuss an appropriate reapplication interval for your use.

Can I Apply More Than the Recommended Rates for a Greater Impact?

We recommend that you apply the products at recommended label rates, as those are designed to give you the most benefit and greatest return on your investment in this technology.  The plants interact with the mycorrhizae by their own reactions, so the amount of colonization of mycorrhizae is based on the plant’s needs.  Since the plant is not associating with more mycorrhizae than it needs, applying more than the recommended rate will not produce a greater impact.  That being said, there have not been any adverse effects of over-inoculation documented, so if you choose to apply more than is recommended, it will not hurt your plants.

Can I Still Use Fungicides if I Apply Mycorrhizae?

Yes. An extensive list of fungicides may be used with mycorrhizae without negative impact. The longer you wait to apply a fungicide after mycorrhizal inoculation, the better it will be for the mycorrhizal establishment and development. Consult the list below for a full listing of fungicides that are safe to use. If a fungicide’s effect on mycorrhizae is unknown, we recommend applying after the establishment of the relationship between the plant and mycorrhizae, typically 3-4 weeks. You can also apply the fungicide before the application of mycorrhizae and wait a week before adding the mycorrhizae.

To view the interactions between many Horticulture and Turf fungicides and mycorrhizal fungi: CLICK HERE

For Agricultural fungicide interactions with mycorrhizal fungi, please consult with your crop adviser or contact the Valent BioSciences Biostimulant Unit.

Can I Use Mycorrhizae if the Fungicide I Use is Listed as Harmful to Mycorrhizae?

There are many ways in which mycorrhizae can still benefit your plants or crops if you utilize a fungicide that is listed as harmful to mycorrhizae.

For general Tips and Observations for using Fungicides in conjunction with mycorrhizae:  CLICK HERE

For Agricultural fungicide interactions with mycorrhizal fungi, please consult with your crop adviser or contact the Valent BioSciences Biostimulant Unit.

How Long Will the Mycorrhizae Impact My Plants?

The mycorrhizae will remain in a symbiotic relationship with the plant for the entire life of the plant.  If a shrub is treated at a greenhouse or nursery, then transplanted into a customer’s landscaping, the mycorrhizae will also be transplanted with the plant and will continue to help the plant thrive for its entire life.

What is the Shelf Life of MycoApply®?

The shelf life of MycoApply® products is 2 years from the time of production.  If you use a partial bag of MycoApply, we recommend that you store the product in a cool and dry location and keep the packaging closed to maximize efficacy and shelf life.

How Should MycoApply® be Stored?

MycoApply® can be stored under normal warehouse conditions. Refrigeration is not needed.

Can Mycorrhizae be Used with Other Biological Products?

Yes.  Mycorrhizae work well with other biological products, including beneficial bacteria (such as Actinovate), and Trichoderma (such as RootShield).  They will not harm the mycorrhizae, and in some cases, synergistic effects have been observed.

What is the Difference Between the Hyphae Formed by Mycorrhizae and a Root Hair?

Root hairs grow to a maximum length of a few millimeters, whereas the hyphae formed by the mycorrhizae can reach lengths of 25 inches.  Fungal hyphae can absorb nutrients and water along their entire length, which is in contrast to root hairs which only absorb nutrients at the tips.  Fungal hyphae can also absorb nutrients from both the soluble and insoluble pool, compared to root hairs which are limited to absorbing nutrients from the soluble pool.

I Buy My Germination/Propagation Mix and Cannot Incorporate Anything During my Flat Filling. How Can I Apply my Mycorrhizae?

If you cannot incorporate the mycorrhizae into your mix before flat filling, you could apply as a plug dip or drench to the plug/propagation trays before planting the flats.

For our recommended rates for Drench Applications, please refer to this resource:  MycoApply Drench Recommendation Chart

I Buy My Plugs and Rooted Propagation Plants. How Can I Use Mycorrhizae?

You could apply the mycorrhizae as a plug dip or drench before transplanting.

For our recommended rates for Drench Applications, please refer to this resource:  MycoApply Drench Recommendation Chart

Can Mycorrhizae be Combined with Other Products in My Drench?

Yes, mycorrhizae can be combined with other products in your drench, just take care to not include a fungicide that is not listed on our ‘safe’ list and make sure the application rate for the mycorrhizae follows suggested guidelines.  Mycorrhizae are not impacted by pesticides, herbicides, or nematocides.  Mycorrhizae work well with other biological products, such as beneficial bacteria and Trichoderma.

What is the Recommended Fertility Program if I Use Mycorrhizae?

High levels of water-soluble nitrogen and phosphorus suppresses most mycorrhizal activity because it reduces the mutual needs of the host and the fungus.  Plants that experience stress during production often develop a stronger relationship with their associated mycorrhizae.  Controlled release and organic forms of fertilizers release their nutrients very slowly and do not increase the water-soluble nutrients in the substrate excessively.  If you are accustomed to using an injector for constant feed programs, then use a fertilizer that is low in phosphorus and has a high percentage of nitrate-nitrogen.  Consider reducing the 200-300 ppm N to 100-150 ppm N for a comparison.  If you must apply a high phosphorus analysis fertilizer, we recommend applying it three or more weeks after inoculation to avoid inhibiting the mycorrhizal colonization.

Should I Feed My Mycorrhizae?

There is no need to feed mycorrhizae.  The plant feeds them!  It’s the excess sugars produced by the plant through photosynthesis which are released from the plant roots that feed the growth of mycorrhizae and mycorrhizal filaments. (There are synthetic compounds that can act as a catalyst to cause mycorrhizae to germinate, but they are unnatural, expensive, and not commonly available.)  Please see the FAQ above entitled “What is the Recommended Fertility Program if I Use Mycorrhizae?” for recommendations regarding your fertility program in concert with mycorrhizal inoculation.

Will MycoApply® Work in My Local Garden, Nursery, Greenhouse, or Agricultural Field?

Mycorrhizal fungi are generalists and are able to provide benefits to plants in many different locales and circumstances. Local differences such as soil type, pH, temperatures, moisture levels, etc. will not rule-out the effectiveness of these symbionts, and the species that we have selected for our MycoApply products are found in natural association with plants across North America, as well as across the globe.

Can MycoApply® Products be Specified in Landscaping and Restoration Jobs?

Absolutely!  In fact, the use of mycorrhizal fungi to reinstate positive soil biology in landscaping and restoration is quickly becoming a staple in these industries.

For tips and guidelines on specifying mycorrhizal inoculants: CLICK HERE