The management of biologicals in rootzone media

1. Sunday, February 17, 2019 Jerry Spencer BSC Hons Soil Science, Grad Dip
Gilba Solutions Pty Ltd Mobile 0499975819 PO Box 45 Maroubra 2035 ABN 87163656228
ACN 163 656 228 Skype aussiefert Website: https://herbycides.wixsite.com/gilba
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BIOLOGICALS IN ROOTZONE MEDIA
In agriculture and in the Australian turf industry there are a number of products offering a solution
to boosting what are termed beneficial organisms in the soil profile. The theory on the vast majority
of these is a good one but in practice there is little by way of independent trial data showing that
they actually do what they say they will.
The reasons for this are very simple.
1. At the rates that it is proposed for application on many of these the chances of an
introduced microorganism thriving and becoming dominant are at best minimal.
2. Little if any consideration is taken in relation to applications of chemicals and their non
target effect on these beneficial organisms.
Trichoderma spp are fungi that are present in nearly all soils and other diverse habitats. In soil, they
frequently are the most prevalent culturable fungi. They are favoured by the presence of high levels
of plant roots, which they colonize readily. Some strains are highly rhizosphere competent, i.e., able
to colonize and grow on roots as they develop. The most strongly rhizosphere competent strains can
be added to soil or seeds by any method. Once they come into contact with roots, they generally
colonize the root surface. Coupled with this Trichoderma spp attack, parasitize and otherwise gain
nutrition from other fungi. Since Trichoderma spp grow and proliferate best when there are
abundant healthy roots, they have evolved numerous mechanisms for both attack of other fungi and
for enhancing plant and root growth.
Little if any consideration is taken in relation to applications of chemicals and their non target
effect on these beneficial organisms.
In reality these products are applied and then little if any attention is given to how for example
fungicide applications may affect the very organisms that you are trying to encourage. Both
Mycorrhizal fungi and trichoderma sp can be sensitive to fungicides and bearing in mind that there
are two major groups of mycorrhizal fungi, VAM and Ecto-, fungicides detrimental to one group,
need not be detrimental to the other. To further complicate the issue some fungicides may actually
stimulate mycorrhizal fungi!
General Rules Regarding Use of Fungicides with Mycorrhizal Fungi Inoculants:
1.Generally, foliar application of non­systemic fungicides have very little impact on mycorrhizal
fungi, which reside on the roots. Even though some fungicide material may reach the soil, the
amount reaching the actua l rootzone I susually too low to have any significant, long‐term effect on
mycorrhizal fungi.
2. Soil drench applications of non­systemic fungicides can be detrimental to mycorrhizal fungi
particularly if applied before root colonization takes place. This method places the greatest
fungicidal load at the root zone and is therefore the method most likely to cause harm to
mycorrhizal fungi. Because of this, it is important to avoid using soil drench fungicides too

2. Sunday, February 17, 2019 Jerry Spencer BSC Hons Soil Science, Grad Dip
Gilba Solutions Pty Ltd Mobile 0499975819 PO Box 45 Maroubra 2035 ABN 87163656228
ACN 163 656 228 Skype aussiefert Website: https://herbycides.wixsite.com/gilba
Page2
close to inoculation time, so a good timeframe would be to avoid using soil drench fungicides 2
weeks before inoculation (longer if systemic) and 4 weeks after inoculation.
Once spores have thoroughly colonized the roots, mycorrhizal fungi tend to be less
sensitiveto detrimental, non­systemic fungicides applied by soil drench because:
a. fungicide levels will be high in the soil, but tend to be considerably lower inside root
tissue.
b. high levels of fungicides in soil can kill off fungal tissue in the soil, but not fungal tissue
embedded inside the root.
c. when fungicide levels in soil diminish from leaching or gradual degradation, fungal tissue
inside the root will grow a new absorbing network out into the soil to restore the
mycorrhizal effect.
3. Foliar or soil applications of systemic fungicides can lead to accumulation of fungicide in
the root tissue having a negative impact on mycorrhizal fungi. In general, roots of treated
plants are not susceptible to colonization
Fungicide Active
Ingredient
Effect on ecto
mycorrhizal fungi
Effect on VAM
mycorrhizal fungi
Effect on
trichoderma sp
Azoxystrobin None Negative
Captan None Generally negative Negative
Chlorothalonil Generally negative Negative
Fludioxonil None
Fosetyl aluminium None Negative
Iprodione Negative None
Mancozeb Negative None
Metalaxyl None Negative
Paclobutrazol None
Propamocarb None
Propiconazole Negative Negative
Terrazole Negative
Triadimenol Negative
However, it must be realised that all Mycorrhizal fungi and trichoderma sp do not behave the same
despite numerous claims. The take away message from this is don’t believe promotional claims look
for supporting independent research!
Recent trial work with an arbuscular mycorrhizal fungus, Glomus iranicum var. tenuihypharum var.
nova, on a mixed Poa/Agrostis sward gave interesting results.

3. Sunday, February 17, 2019 Jerry Spencer BSC Hons Soil Science, Grad Dip
Gilba Solutions Pty Ltd Mobile 0499975819 PO Box 45 Maroubra 2035 ABN 87163656228
ACN 163 656 228 Skype aussiefert Website: https://herbycides.wixsite.com/gilba
Page3
Although not statistically valid results showed increased root length, improved turf quality, an
increased median and maximum number of roots, an increase in root width, and an increase in the
number connected components.
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6
7
8
9
10
11
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Control Mycoup
Mean maximum root length cm post
treatment
0.62
0.63
0.64
0.65
0.66
0.67
0.68
Control Myco-up
Post treatment NDVI
Mean width
(um)
Max Number
roots
Number of
Connected
Components
Median
Number of
roots
Control 23.21 39.75 40.16 27.91
Myco-up 27.23 44.33 55.75 34.58
0
10
20
30
40
50
60
Impact of mycoup on root architecture

4. Sunday, February 17, 2019 Jerry Spencer BSC Hons Soil Science, Grad Dip
Gilba Solutions Pty Ltd Mobile 0499975819 PO Box 45 Maroubra 2035 ABN 87163656228
ACN 163 656 228 Skype aussiefert Website: https://herbycides.wixsite.com/gilba
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References available upon request