Metarhizium Fungi Impact On Agriculture - Dr. Mary Barbercheck, Penn State, from the 2020 Conservation Tillage and Technology Conference, held March 3-4, 2020, Ada, OH, USA.

1. Mary Barbercheck,
meb34@psu.edu
Dept. of Entomology
Fantastic Endophytic Fungi
What they are, what they do,
and how to conserve them

2. Overview
• What is an endophyte?
• What do they do?
• A novel endophyte: Metarhizium
• Effects of crop management
• Crops and cover crops
• Soil properties
• Tillage
• Pesticides
• Summary and conclusion

3. What is an endophyte?
Greek: Endo = within + phyte = plant
• Bacterium or fungus that lives within plant tissues without causing
apparent plant disease
• All plants studied to date host endophytes
• Potentially very important but understudied
– only a minority of endophytes have been characterized
• A single plant tissue (leaf, stem or root) can harbor many different
species of endophytes, both bacterial and fungal
http://regent.jcu.cz/amms/pl8FE1.jpg
Mycorrhizal fungus in root
http://bugs.bio.usyd.edu.au/learning/resources/Mycology/im
ages/Topics/Plant_Interactions/Endophytes/fungiOnBanksi
a.jpg
Fungal endophyte growing
out of leaf
https://upload.wikimedia.org/wikipedia/com
mons/9/93/Epichloe_typhina.JPG
Epichloë typhina
on KY bluegrass

4. Potshangbam, M., et al. 2017. Front. Microbiol. 8:325. doi: 10.3389/fmicb.2017.00325
Endophytes are everywhere!

5. What are some benefits of plant-fungal
endophyte interactions?
Benefits to endophyte
• Plants use sunlight,
water and CO2 to
produce sugar and O2
• Sugars and nutrients
transferred to roots
• Excess nutrients
exuded from root tips
• Endophyte gains a
protected environment
in which nutrients
(sugars, N) are readily
available https://nosprayhawaii.com/education/about-soils/what-are-microbes/
https://tse2.mm.bing.net/th?id=OIP.qKbVjFlWxT1JAoAA3KHXZQHaF3&pid=Api/

6. What are some benefits of plant-fungal
endophyte interactions?
Benefits to plants
• Increased “root” volume”
• Increased shoot and/or root growth
• Increased overall hardiness
• Improved plant response to environmental
stress, e.g., heat, drought, and salt
• Enhanced uptake of minerals (P, N, Zn, Mg)
• Enhanced N use efficiency
• Enhanced tolerance or resistance to plant
pathogens or insect pests
– produce chemicals that inhibit the growth of pest
organisms
– increase expression of defense-related genes in
plants, making plants tolerant or resistant to
potential pests https://tse4.mm.bing.net/th?id=OIP.bF-
E1j48fyehqGooPBGxigHaK1&pid=Api

7. Arbuscular Mycorrhizae: Root-Fungus Symbiosis
mycor = fungus, rhizae = root
• Probably the most abundant fungi
in ag soils, between 5 and 50% of
the microbial biomass
• Benefits to the fungus
– Source of sugar (“fixed” carbon)
• Benefits to the host plant
– Increased nutrient uptake
• Esp. immobile nutrients, P,
Zn
– Increased disease and insect
tolerance/resistance
– Enhanced water relations
• Benefits to the soil
– Stabilization of soil aggregates
– Contribute to soil C
Arbuscule

8. Mycorrhizae enhance aggregate stability, soil C
Stained
glomalin on
soil aggregate
and infected
roots

9. Practices that influence mycorrhizal fungi
Beneficial practices
• Perennial crops
• Rotation with host
crops
• Over-wintering
cover crops
• Reduced tillage
• Low fertility inputs
Detrimental practices
• High fertility inputs
(esp. P)
• Pesticides (fungicides,
herbicides)
• Frequent inversion
tillage
• Long bare fallow
• Non-host crops (e.g.,
brassicas, buckwheat)

10. Endophytic Insect-Pathogenic Fungi
• Common insect-
pathogenic fungi now
known to be
endophytes
• Beauveria bassiana in
corn provided season-
long suppression of
European corn borer (Lewis
and Cossentine 1986)
• Metarhizium colonizes
rhizosphere and roots
(Sasan and Bidochka 2012)
http://www.westatic.com/img/dict/srsbz/images/00110-1.jpg; http://www.bioworksinc.com/images/products/mycotrol-o1.jpg

11. Entomopathogenic Fungi
entomo = insect pathogenic = causing disease
• Fungus that
parasitizes insects
• Infectious agent is
usually spore
• Commonly isolated
from soil
• High spatial and
temporal diversity

12. Insect-Pathogenic Fungus Life Cycle
https://plant-health.co.za/wp-content/uploads/2019/08/KL-MR-mode-of-action-figure.jpg
https://www.researchgate.net/profile/Narit_Thaochan2/publication/301731856/figure/fig1/AS:356507381190656@1462009391231/The-infection-process-of-
Metarhizium-guizhouense-on-rice-moth-larvae-Corcyra.png

13. How endophytes affect insects
Gange et al. 2019. New Phytologist 223:2002-2010
Measure Entomopathogenic
Endophyte
Non-
Entomopathogenic
Endophyte
Insect abundance
Reproductive rate
No Net Effect
Larval survival
Larval weight
Amount of plant eaten
No Net Effect
Insect choice of plants

14. How endophytes affect insects
Gange et al. 2019. New Phytologist 223:2002-2010
Insect Feeding Type Entomopathogenic
Endophyte
Non-
Entomopathogenic
Endophyte
Chewing
No Net Effect
Sucking
Mining No Net Effect
Galling No Net Effect

15. Metarhizium (Hypocreales: Clavicipitaceae)
Cosmopolitan Insect-Pathogenic Fungus
• 9 species (Bischoff et al. (2009) Mycologia 101: 512-530)
• Large diverse group spans mutualistic plant symbionts and
parasites of plants, insects, and other fungi (Spatafora et al. (2007) Mol. Ecol. 16: 1701-
1711)
• Can form endophytic relationship with plants
http://www.discoverlife.org/nh/maps/Fungi/Ascomycota/Clavicipitaceae/Metarhizium/map_of_Metarhizium_anisopliae.jpg

16. https://www.researchgate.net/figure/269420425_fig1_Fig-1-Overview-of-the-basic-life-cycles-of-B-bassiana-and-M-robertsii-Both-fungi-are
featured-image-fungus.png. Behie et al. 2012. DOI: 10.1126/science.1222289.
https://butterfliesandscience.files.wordpress.com/2012/07/larva-infected-with-fungus.jpg
Lifestyles of Metarhizium

17. • Insect pathogen
• Root zone colonizer
and endophyte
• Plant growth
promotion
• Insect growth
suppression
• Plant disease
suppression
• Nutrient transfers
Multifunctional Metarhizium

18. Metarhizium-plant interactions
.
- Metarhizium + Metarhizium
Ortiz-Urquiza, A. et al. 2015. Appl. Microbiol. Biotechn .99:
1057-1068; . Liao et al., 2017. Microbiology 163: 980-991

19. Methods
Identification
TEF1
Plant Defense
Gene Expression
Identification
TEF1

20. Metarhizium recovered from 91% of V4 maize plants
Detection from both root + leaf > only root or only leaf
0
10
20
30
40
50
60
70
80
90
100
Leaf Only Root Only Leaf + Root
%EndophyticPlants
Recovery of M. robertsii
n=116 ; F2,15 = 17.7, P = 0.0013No recovery from control plants, DNS

21. Mean height and biomass
Metarhizium-treated seed > control
89
89.5
90
90.5
91
91.5
92
92.5
Exposed +
Detected
Exposed + Not
Detected
Control
cm
Height (cm)
a
ab
b
5.4
5.6
5.8
6
6.2
6.4
6.6
Exposed +
Detected
Exposed + Not
Detected
Control
gm
Aboveground Dry Biomass
(gm)
a
ab
b
F2,227 = 3.73; P = 0.03 F2,211= 3.78; P = 0.02

22. Mean relative growth rate
‘Exposed and Detected’ < Control
0.41
0.415
0.42
0.425
0.43
0.435
Exposed + Detected Exposed + Not
Detected
Control
RelativeGrowthRate
2nd Instar Black Cutworm
ab
a
b
F2,211 = 4.66; P = 0.01

24. Detection in corn > soybean, wheat
0
2
4
6
8
10
12
14
16
18
Maize Soy Wheat
%InsectInfection
Cash Crop

25. Metarhizium in Cash Crops
Positive Environmental Correlations
Labile C (“Active C”)
• Underrated source of C for
soil fungi (De Vries and Caruso, 2016)
• Metarhizium may persist or
recycle on decomposing
organic matter
• Metarhizium plays a role in
decomposition of labile
organic matter in soil?
• Mycorrhizal fungi
contribute to the direct
loss of soil C by acting
as decomposers (Talbot et al.,
2008)
http://cdn.thinglink.me/api/image/951039355135197187/1024/10/scaletowidth/0/0/1/1/false/true?wait=true
https://ask.extension.org/uploads/question/images/attachments/000/028/230/Soil_original.JPG?1472584417

26. Metarhizium in Cash Crops
Positive Environmental Correlations
Electrical conductivity
• Correlates with multiple soil properties that affect crop
productivity
• May be an integrator of multiple characteristics
• soil texture
• cation exchange capacity (CEC)
• water holding capacity
• organic matter level
• AMF distribution in soil profile and diversity positively
related to EC (Liu et al. 2016)

27. Winter-hardyWinter-tender
Red Clover Cereal RyeCanola
Austrian Winter Pea Forage Radish Oats
Winter Cover Crop Cocktails
Legumes Brassicas Grasses

28. Cover Crop Diversity Not Related to Metarhizium
Diversity or Detection
of M. robertsii in Cover Crops
0
5
10
15
20
25
30
35
40
45
Pea
O
atFallow
4Spp3SppW
7Spp
CloverRadish
6Spp3SppN
RyeCanola
%Metarhizium
Randhawa et al., 2018Cover Crop Treatment: F11,265=1.5, P = 0.1309

29. 0
5
10
15
20
25
30
35
Legum
e
Fallow
G
rass
M
ix
Brassica
%DetectionMetarhizium
• Cover crop treatment: n.d.
• Mono vs Polyculture: n.d.
• Brassicas < Legumes (p =
0.0146)
• Proportion brassicas in
cover crop mixtures in fall
negatively related to
Metarhizium (p = 0.0247)
• Proportion cereal rye in
spring negatively related to
Metarhizium (p = 0.0006)
Plant Functional Group, Not Diversity, Matters
Functional Group: F4,274=2.58, p=0.0365

30. Metarhizium Detection in Brassicas < Legumes
Negative Correlation with Cereal Rye
• Different plant species and genotypes host specific
microbial communities (Aira 2010 , Berendsen 2012, Chaparro et al. 2012)
• Consistent with known effects of brassicas on soil
microorganisms (Vukicevich et al., 2016)
• Endophytic or rhizospheric growth of Metarhizium
suppressed by brassicas?
• Inhibition by glucosinolates or other secondary metabolites? (von Roepenack-
Lahaye et al., 2004)
• Lower occurrence of Metarhizium spp. in root isolations of cabbage
compared to roots of cereal rye (Steinwender et al., 2015)
• Metarhizium conidia exposed to 100 ppm glucosinolates did not germinate
(Klingen et al., 2002)
• Cereal rye allelochemicals, e.g., benzoxazinoids, contribute
to the negative association with Metarhizium? (Schulz et al., 2013)

31. Metarhizium in Cover Crops
Positive Environmental Relationships
• Fall CC Biomass
• Spring Weed Biomass
– Early season resource
• Soil Moisture
– Needed for germination of
spores, mycelial growth,
and sporulation
• % Silt and Clay
• Clay protects conidia from
degradation
• Soil Calcium

32. In cover crops, positive correlation with soil calcium
Ca in soil may support survival and population growth
directly
• Calcium required for sporulation, spore germination, oriented hyphal
tip growth, and hyphal branching (Berridge et al., 2000; Wang et al., 2012)
As a rhizosphere resident, Metarhizium may increase
bioavailability of Ca
• Produces oxalates that solubilize nutrients by secretion of acidic
compounds, requires presence of Ca2+
(Gadd et al. 2014; Jacoby et al. 2017; Takeshita et
al., 2017)
• Fungal calcium oxalate, abundant, ubiquitous (Gadd et al. 2014)
• Precipitates of calcium oxalate can serve as significant
calcium reservoir in soil (Graustein et al., 1977)
• Metarhizium solubilized calcium phosphate in vitro, wheat
seedlings grew faster in treatments with Metarhizium (Liao et al.
2014)

33. Metarhizium in Cover Crops
Negative Environmental Relationships
Negative correlations
• % Sand
– Likely related to
moisture
– Mean 27.5% sand
– Range 14 – 50%
• No. days since
disturbance
– Development of
patchy distribution

34. Range of Tillage Systems
Conventional
Tillage
Reduced
Tillage
<30% Soil
Residue
Cover
Reduced (Conservation) Tillage
>30%Soil Residue Cover
Mold-
board
Plow
Heavy
Offset
Disk
Non-
conservation
Tillage
Other
Tillage
Systems
Ridge
Till
Chisel
Plow
Strip
Till
No-Till
Increasing Residue Covering Soil
Decreasing Intensity and Frequency of Soil Disturbance
Adapted from A. McGuire, Washington State University, MWPS-45
Not all conservation tillage systems the same
Can affect pests and beneficials
May or may not involve cover crops in rotation

35. Detection of Metarhizium greater in
inversion vs non-inversion tilled soil
0
5
10
15
20
25
30
1 (cover) 2 (soy) 3 (corn)
year of transition
Full Till
Minimum Till
#insectskilled
Hypothesis:
Greater detection occurs in full
tillage due to more spread &
mixing of soil. Truscott & Gilligan 2001
Full Till = Moldboard plow
Min Till = Chisel plow and disk
Tillage p = 0.0684
Jabbour, R., Barbercheck, M. 2009 Biological Control 51: 435-443.

36. Metarhizium in Chisel Plow > No-Till
in a Long-Term Cropping Systems Trial
Kepler et al. 2015. Environmental Microbiology doi:10.1111/1462-2920.12778
0
5
10
15
20
25
30
35
Chisel Plow No-Till
CFUMetarhizium/100ul
*

37. Number Disturbances vs Detection of
Metarhizium
Number of Disturbances

38. Pesticide Suppression of Metarhizium
Active Ingredient Type of Pesticide Commercial Name
1Mancozeb
1Tebuconazol
1Copper oxychloride
1Chlorothalonyl
Fungicide Manzate, Dithane
Folicure
Cuprogard
Daconil
2Azoxystrobin
2Captan
2Dimethomorph
2Pyraclostrobin
2Thiophanate-methyl
2Triflumizole
2Triflozystrobin
Fungicide Dynasty
Captan
Acrobat
Headline, Stamina
Pestanal, Topsin
Terraguard, Procure
Armada, Flint
3Metalaxyl+mancozeb Fungicide Ridomil, Allegiance,
Delta-Coat AD
Subdue 2E
1
Mochi et al. 2005. Neotropical Entomology 34:961-971
2Bruck. 2009. BioControl 54:597-606
3
Akbar et al. 2012. African Journal of Microbiology Research Vol. 6: 3956-3962

39. Pesticide Suppression of Metarhizium
Active Ingredient Type of
Pesticide
Commercial Name
1Ametryn
1Glyphosate
1Trifluralin
Herbicide Evik, Amatrex
Roundup
Treflan
2Acetameprid
2Cypermethrin
2Imidacloprid
Insecticide Intruder, Tristar
Fury, Mustang Max
Gaucho
3Chlorpyrifos
3Lufenuron
3Profenofos
Insecticide Lorsban, Nufos
Program
Curacron, Selecron
1
Mochi et al. 2005. Neotropical Entomology 34:961-971
2
Bruck. 2009. BioControl 54:597-606.
3Akbar et al. 2012. African Journal of Microbiology Research Vol. 6: 3956-3962

40. Effects of Organic Pesticides
• Metarhizium compatible with
spinosad (Akbar et al. 2012)
• Metarhizium highly susceptible to
mycoparasites Clonostachys spp.,
Trichoderma harzianum,
Lecanicillium lecanii (Krauss et al. 2004)
• Azadirachtin (Neem) toxic to
Metarhizium (Niassy et al. 2012)

41. Summary and Management for Conservation
• Rotation
– Endophytes more common in some crops than others, e.g., corn
• Winter cover crops can help conserve endophytes
– Legume cover crops appear to favor Metarhizium
– Brassica, cereal rye cover crops appear to suppress Metarhizium
• Soils with good fertility, moisture-holding capacity,
active organic matter favor Metarhizium
• A little tillage is ok, helps distribute spores through
soil
• Some pesticides are suppressive to Metarhizium

42. Summary
• Endophytes are common and beneficial
– germinating seeds recruit particular microbes and establish
beneficial associations
• Conservation of endophytes in agroecosystems
could potentially result in
– Reduced need for fertility and pest management inputs
– crops better able to tolerate and recover from environmental and
biological stresses
• Still learning how management practices and soil
characteristics affect endophytes
• Research can inform strategies by which
endophyte communities may be manipulated to
suppress pests and promote plant health

43. Acknowledgement
Project Team
Imtiaz Ahmad
Brianna Flonc
Christy Voortman
Puneet Randhawa
Maria Jimenez-Gasco
Dawn Luthe
Mary Barbercheck
Brosi Bradley
Mac Burgess
Alan Cook
Sarah Cornelisse
Dan DeTurk
Tianna DuPont
Franklin Egan
Katie Ellis
Wade Esbenshade
Denise Finney
Scott Harkcom
Dave Hartman
Mena Hautau
Jermaine Hinds
Mitch Hunter
Shan Jin
Jason Kaye
Nancy Ellen Kiernan
Dave Mortensen
Jeff Moyer
Ebony Murrell
Barbara B. Padro
Meagan Schipanski
Brian Snyder
Dayton Spackman
Alexandra Stone
Charlie White
Dave Wilson
Leslie Zuck
Bucky Ziegler
USDA Organic Research and Extension
Initiative (OREI)
USDA Organic Transitions (ORG)
USDA NE-IPM
NE-SARE Graduate Student Grants
Penn State College of Agricultural
Sciences Seed Grant

44. Thanks!

45. Base 3-year Crop Rotation
Mean Number of Days in Each Phase
Wheat, 291
Post-wheat
fallow, 16
Pre-corn
cover crops,
263Pre-corn
fallow, 16
Corn, 140
Post-corn
fallow, 5
Pre-soy cover
crops, 228
Pre-soy
fallow, 19
Soy, 149
Post-soy
fallow, 4

46. Significant Soil Properties for M. robertsii Detection
Forward Selection Multiple Regression, 22 variables, n = 1,295
r2
adj for model = 0.136
Soil Variable r2
adj F p
% Soil Moisture (+) 0.044 85.35 <0.0001
% Silt (+) 0.085 57.93 <0.0001
% Clay (quadratic; optimum = 30%) 0.028 18.04 0.0002
P (+) 0.021 18.08 <0.0001
Electrical Conductivity (mS/cm)
(quadratic; optimum = 185 mS/cm)
0.032 6.72 0.0096
Permanganate Oxidizable C (“Active C”)
(quadratic; optimum = 55 ppm)
0.048 4.62 0.0317
Sulfur (quadratic; optimum = 48 ppm) 0.056 4.39 0.0363

47. Summary: Soil Factors
• Soil P (r2 = 0.021)
• Low P availability major constraint to plant growth,
performance, and metabolism due to poor solubility and
mobility in soil
• Fungi can promote plant P acquisition by different
mechanisms, e.g., P solubilization, P mineralization, hyphal
P transfer.
• N, P, Ca, Mg and K concentrations from seeds harvested
from cowpea plants sprayed at flowering with M.
anisopliae > control plants (Ngakou et al. 2007)
• Potato plant P content and biomass grown in soil with M.
brunneum > control plants (Krell et al. 2018)

48. Height of V4 maize correlated with proportion of leaf and root tissue sections
from which M. robertsii recovered
r2
Adj = 0.02; P = 0.02 r2
Adj = 0.02; P = 0.014

49. RGR of BCW negatively correlated with proportion of
endophytic leaf and root sections
r2
Adj = 0.02; P = 0.03 r2
Adj = 0.02; P = 0.03

50. Biomass of V4 maize correlated with proportion of root, but not leaf,
tissue sections from which M. robertsii recovered
r2
Adj = 0.03; P = 0.006

51. SA-response pathway
0
0.5
1
1.5
Control Treated
pr5• pathogenesis-related protein
5 (pr5) up-regulated in leaf
tissue
• pr5 implicated in plant
disease resistance and
antifungal activity
• Possible role in activating
other defense pathways
(El-kereamy et al., 2011)
• Plant may perceive M.
robertsii as a biotrophic
pathogen (Thaler et al., 2012)

52. Endochitinases
0
5
10
15
20 Endochitinase A
0
0.2
0.4
Control Treated
pr4
• endochitinase A and
pathogenesis-related protein 4
(pr4)
• trigger plant defense against
phytopathogens
• antagonistic to plant defense against
herbivores
• endochitinase A up-regulated
• defense against chitin-containing
fungal pathogens
• plant perceives M. robertsii as
biotrophic pathogen?
• pr4 down-regulated
• antifungal chitin-binding protein,
defense against necrotizing
pathogens, salt, wounding, and other
stresses

53. Recovery of M. robertsii : % of tissue sections plated
0
10
20
30
40
50
60
Leaf Root
%TissueSections
% Recovery by Tissue Sections Plated
Recovery from root sections (43%) > leaf sections (29%)
leaf n=678, root n=678; F1,171 = 19.7, P < 0.0001

54. Metarhizium Frequency of Detection Across
Experiments (2003 – 2015)
*Factors significant in multiple regression analysis
0
5
10
15
20
25
30
35
40
Soy
W
heat
Tim
_Clov
C
orn
R
ye
R
ye_H
V
Alf
Alf_G
rass
%Metarhizium
a ab b b b
b b
a
Plant Species
n= 981; F = 6.93, P<0.0001

55. Metarhizium Frequency of Detection Across
Experiments: Soil Characteristics
*Factors significant in multiple regression analysis
Electrical Conductivity
n= 991; P<0.0001; r2
adj= 0.1079
“Active” Labile C
n= 991; P<0.0001; r2
adj= 0.0727
Arc(SqRt) = 0.227767 +
0.0020515*Mean EC -
0.0000114*(Mean EC-99.8909)2
Arc(SqRt) = -0.011919 +
0.001189*POC (ppm)
Arc(SqRt) = 0.1991805 +
0.0014997*Mg (ppm) - 4.8715e-
6*(Mg (ppm)-146.247)2
Mg
n= 727; P<0.0001; r2
adj= 0.1196

56. Metarhizium Frequency of Detection Across
Experiments: S, Cu, Zn
* Not significant in multiple regression
Arc(SqRt) = 0.085 + 0.034*S -
0.003*(S-10.413)2
S
n= 728; P<0.0001; r2
adj= 0.2175
Arc(SqRt) = 0.428 - 0.006*Cu
Cu
n=728; P<0.0005; r2
adj= 0.0153
Arc(SqRt) = 0.172 + 0.164*Zn -
0.0553*(Zn-1.466)2
Zn
n= 728; P<0.0002; r2
adj= 0.0678

57. Summary from Cross-Project Comparisons
• Plant species
• Different plant species host specific microbial communities
(Berendsen 2012)
• Structure of rhizosphere maize microbial communities
depended on plant genotype (Aira 2010)
• Plants can shape soil microbial communities through
secretion of root exudates (Chaparro et al. 2012)
• Mg
• Metarhizium endophytic infection increased leaf
concentration of Mg in cowpea (Golo et al. 2014)
• Nutrient transfer?
• Pathogenicity, lipase activity of M. anisopliae enhanced in
Mg-amended medium (Ali et al. 2009,Jaworska and Gospodarek 2009; Sabbour
2002)
• Lipase used during infection process to breach insect cuticle

58. Conventional vs Organic
Multiple linear regression for number of CFU
of M. anisopliae s.l. in Iowa, 2011
Clifton et al. (2015) PLoS ONE 10(7): e0133613
Variable Slope SE F p
Total Soil N (%) -7.47 2.87 6.75 0.01
Tillage -1.16 0.37 9.76 <0.01
Conventional Field
+ Herbicide
-0.89 0.34 6.75 0.01
Conventional Field
Margin
-0.86 0.34 6.12 0.01
% Silt 0.02 0.01 6.88 0.01
Organic Fertilizer 1.45 0.47 9.57 <0.01

59. Soil Disturbance and Residue Cover
Full tillage
Moldboard plow based
Minimum tillage
Chisel plow/Cultivator

60. June 1, 2011 June 3, 2011
Hairy Vetch Cereal Rye

61. Some Environmental Factors That
Affect Pathogen Populations within a
Habitat
Abiotic Factors
• Moisture
• Temperature
• Disturbance (e.g.,
tillage)
• Soil texture/structure
• Soil chemistry
• Soil atmosphere
• Surface residue
• Pesticide use
• Fertility source
• UV light
Biotic Factors
• Pathogen species
(e.g., host range,
behavior, virulence)
• Host availability and
behavior
• Predators and
antagonists
• Competitors
• Plant diversity
• Food plant of host
insect
(Stuart et al. 2006; Barbercheck & Hoy 2005)

62. JA response-pathway
0
0.2
0.4
0.6
0.8
1
mpi
• Down-regulation of
maize protease
inhibitor (mpi), a
downstream marker
• Accumulates in
response to
mechanical wounding,
including insect
feeding
• May reflect non-
response in absence of
insect feeding
Control Treated

63. Plants can drive soil microbial community,
plant susceptibility, tolerance to insects
• Manipulating the soil
microbiome to control
arthropod pests in a
predictable way is
complex
• Need to address
ecological and
organismal processes
at multiple scales,
mediation by
management (Begg et al.,
2017. Crop Protection 97: 145-
158)
DeDeyn & Van der Putten. 2005. Trends in
Ecology & Evolution 20, 625-633.

64. Crop Effects on Metarhizium
Across Projects
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
PerLegum
eLegum
eBi
PerLegum
eBi
Fallow
R
ye
Soy
C
orn
BiSm
G
rain
M
ixLegum
e
SudaxBrassica
bcd
cd cd d d d
cd cd
a
abc
b
n=2,688; F=7.57; P<0.0001
%Infection