Modern biocontrol

1. Modern Biocontrol
Agents and
Biofertilizers
Prof. Mark Laing
Plant Pathology, UKZN
& Plant Health Products (Pty) Ltd

2. Infected Ant

3. The Future is Here, for BCAs
1. Fewer pesticides available
2. A wider range of BCAs
3. Better formulations, shelf-life, simplicity
4. Biofertilizers:
• N fixing – nodules and free-living
• Mobilization of P and micronutrients
• Buffering abiotic stress:
• Tolerance of heat, cold, drought, waterlogging, soil
toxins, toxic metals
5. Soluble silicon - a powerful tool to add

4. Beneficial Microbes for Agriculture
– available of coming soon !
1. Biocontrol Agents to control
• Diseases, pre- and post-harvest - most
• Pests - most
• Nematodes – coming now
Added benefit
– Growth stimulation esp. seed and roots
2. Biofertilizers to enhance fertilization
• N fixation – Rhizobium, Azotobacter, etc.
• P mobilization
• Micronutrient mobilization – Mo, Bo, Zn, Fe

5. What growers need: Registered, commercial BCA
products: effective, affordable, stable, simple

6. Field Crop Soil Problems
• Seed death, damping off and uneven stand
(sub-lethal infection)
• Root diseases of adult plants
– Cause - Pythium, Rhizoctonia, Fusarium spp., Ggt
(take-all)
– Solution - seed treat with Trichoderma (e.g., Eco-T
from PHP)
• It stimulates early germination
• It colonizes the emerging root
• It stimulates more lateral root formation
• It kills incoming pathogens and nematodes
• It degrades allelochemicals in the soil
• It buffers versus abiotic stress factors

7. Biocontrol of Rhizoctonia on
cucumber seedlings

8. Trichoderma coils,
penetrates, kills.
Enzymes digest cell
walls and contents.
Feeding like a spider on
a fly.
D
T
R
B
TP
R
C
T
C
R
A

9. 0
20
40
60
80
100
120Untreated
Cruizeronly
Eco-T
onlyCruizer+
Eco-T
TrichoPlus
only
Cruizer+
TrichoPlus
avg.rootweight
Effects of treatments on root wet weight
A Maize Trial with 2 Trichodermas & Cruiser

10. Mechanisms of Biocontrol
1. Hyper-parasitism (eats fungus)
2. Antibiosis (chemicals that attack pathogens)
3. Competitive displacement (eats
nutrients first)
4. Triggering resistance in host (SAR)
5. Binds iron needed by pathogen
(releases binding agents, siderophores)

11. Kenyan Lisianthus with Fusarium oxysporum
root rot
No treatment
Trichoderma applied weekly

12. Survival(%)
0
20
40
60
80
100
Control
Rhizoc
Tdr+
Rhizoc
Tst+
Rhizoc
Treatment
Survival(%)
TotalDryWeight
0
2
4
6
8
10
Control
Rhizoc
Tdr+
Rhizoc
Tst+
Rhizoc
Treatment
DryWeight(g)
Biocontrol of Rhizoctonia on
cucumber seedlings

15. Foliar Diseases – 2 examples
• Rust biocontrol– fungus Sphaerellopsis filum
attacks pustules and stops carryover – isolate, screen,
register. Studies on biology, epidemiology, efficacy over
seasons, economics of its use, culture conditions.
• Powdery mildew biocontrol - Ampelomyces
quisqualis (AQ). AQ10 was commercialized previously.
PHP has worked out its production but it needs
registration trials.

16. A rust pustule colonized by S. filum
S. filum – black spore
capsules in the old rust
pustule
A new rust pustule

17. Infection of wheat rust spore by S. filum
(Plachecka 2005)
17
Rust
Spore
Rust Spore

18. Ampelomyces quisqualis attacking grape powdery
mildew, U. necator
18
A pycnidium of A. quisqualis
developed inside a spore of pm,
showing the powdery mildew colony
on a grape leaf in the background.
Photos - D. Gadoury
Spores of A. quisqualis emerging
from a pycnidium of A. quisqualis,
formed in place of a pm conidium

19. Post-Harvest vs Moulds and Insects
• Eco-77 – colonize flowers of wheat
and maize to stop Aspergillus &
Fusarium (source of mycotoxins)
• Yeasts: e.g. YieldPlus, B13
• Control of weevils & moths (USDA
too)
– Beauveria bassiana
– Bacillus thurungiensis

20. Untreated
Control
Yeast B13

21. Rice Weevil (Sitophilus oryzae) infected
with Beauvaria bassiana
Rice Weevil (Sitophilus oryzae) infected
with Beauvaria bassiana

22. Insect Pests
• Aphids – Conidiobolus ?
• Caterpillars – Viruses, Btk, Bb
• Bollworm - viruses
• Red spider – Beauveria bassiana
• Thrips – Bb
• Beetles, weevils – Bb, EPNs
• Whitegrubs – B. brognartia, Bb, Bt

23. Beauveria bassiana parasitizing
army worm larvae

24. Beauveria-infected
white grub adult
Beauveria-infected
black vine weevil

25. Dead red spider mites after Eco-Bb x K silicate
on brinjal (Gatarahiya & Laing, 2008)
0
20
40
60
80
100
120
0 1 2
Beauveria rate (g l-1)
%deadmites
(adults+juveniles)
No Si
With Si

26. Bollworm on Wheat Infected by Virus

27. Beetle grub filled with EPN’s
Pictures taken from the University of Florida extension service web-site
http://edis.ifas.ufl.edu/IN468

28. Entomopathogenic nematode entering an insect larva
EPN
Larva

29. Nematode (Eelworm) Biocontrol
• Trichoderma (Eco-T) is suppressive
• Nematode trapping fungi – Clonostachys
rosae eats nematode larvae
• Bacillus thurungiensis strains kill if eaten
• Bayer – Votivo = Bacillus firmus
• Products that eat nematode eggs – to kill
all eggs in top 300mm of soil, requires
2000 kg / ha vs recommended 2kg / ha
• Rotate with a Brassica crop (e.g., canola,
cabbage) – mustard gases released
• Nematodes in sheep and goats !

30. Nematode attacked by a nematode-
trapping fungus

31. 1. Eliminates sub-lethal pathogens
2. Plant hormones released
3. Mineralization – P, Mo dissolved
4. Detoxification – allellochemicals
and metals
5. Environmental buffering
Growth Stimulation by Trichoderma:
Modes of action

32. No
Treatment
Trichoderma

33. Nutrient uptake can be enhanced by
alterations to root structure
Untreated
1.8 area units
Eco-T seed treatment
3.2 area units

34. Eco-T treated maize root
numerous root hairs
Untreated maize root
Few root hairs
Nutrient uptake is enhanced by increased
number of root hairs

37. Root and shoot lengths of perenial
ryegrass (69 days)
0
50
100
150
200
250
Untreated
Treated
Untreated
Treated
Feb planting March planting
Length(mm)
Shoot
Root

38. Abiotic Stress: some Trichoderma
strains and beneficial soil bacteria buffer plants
from extreme environmental conditions:
• Waterlogging
• Drought
• pH extremes
• Nutritional stress
• Pathogen / Environment interaction

39. Eco-T® buffers vs water-logging

40. Effects of soil moisture in lettuce (inoculated with Pythium)
0
100
200
300
400
500
600
700
800Yield(g)wetweight
uninoculated control
inoculated control
biocontrol
Treatments
optimum irrigationhalf double

41. 0
20
40
60
80
Meanwetweight(g)
control(u) control(i) biocontrol
Treatments
6C
12C
18C
24C
30C
Effect of water temperature on biological interactions
in hydroponic lettuce (inoculated with Pythium)

42. 40
60
80
100
120
140
160
Meantotalwetweights(g)
control(u)
control(i)
biocontrol
Treatments
pH4
pH5
pH6
pH7
Effect of pH on disease severity and biocontrol activity

43. Formulations and Applications
• Crucial to activity – eg Bb
• Application must maximize BCA activity
– e.g., Eco-T on seed vs drenching
• Needs to be simple, accurate,
affordable to attract farmers
• Must not conflict with farmer operations
• New approach for field crops – Eco-T in
John Deere talc+graphite lubricant for
planter bins

44. Biofertilizers
• Symbiotic N fixation – only legumes
– Rhizobium nodules
– Promiscuous strains under development for other legumes
– Room storage at 200C
• Free Living N fixation – for all crops
– Azotobacter, Azospirillum sp.
– Burkholderia sp., Klebsiella
• P access, dissolved from clay, rock phosphate
– Bacillus spp.
– Trichoderma
– Mycorrhizae
• Micronutrient access (Mo, Bo, Zn, Cu, Fe)
– Trichoderma
– Mycorrhizae

45. Soybean –
Rhizobium nodules
(Strain WB74)
Red nodule =
fixing N
Green nodule =
parasite !

46. Effect of microbial treatments on Soybean yield
0
500
1000
1500
2000
2500
untreated
Eco-T
1x
Eco-T
2x
Rhizobium
Eco-T
+
R
hizobium
Treatments
Yield(g)
Series1

47. Rhizobium vs waterlogging stress in wattle

48. • N fixation for all the
other crops
• Free-living diazotrophic
bacteria to fix nitrogen in the
root zone
• How much NPK fertilizer can
be replaced by the best
Azotobacter strains ?
• To date: 65% replacement of
normal NPK fertilizer without
affecting normal plant
growth, using best strains
• P solubilization by other
bacteria

49. Figure Increased rooting in treated plants (left)

50. Soluble Silicon in Plant Health
• Silicon deficient soils - >70% of Africa short of soluble Si
• No deficiency symptoms but both physical and
biochemical role in some plants (Si uptake is active)
• Grasses deposit Si as phytoliths into leaves; cane cuts
• Action vs Pests – accelerated resistance
• Action vs Diseases – accelerated SAR (immune system)
• Improves orderly cellulose deposition
• Stress tolerance
– Cold, frost
– Heat
– Drought
– Al, Mn, Cd
• Synergistic with biocontrol agents

51. Typical Opal Phytoliths (maize & grass)

52. Liang, Sun, Zhu, Christie 2006
• Silicon effectively mitigates abiotic
stresses:
– Manganese, aluminum and heavy metal
toxicities
– Salinity
– Drought
– Chilling and freezing stresses
• Mechanisms poorly understood
Abiotic Stress Buffering by Si

53. Cold Stress:
bananas after 40C x 4 days

54. The Future of BCAs
1. Fewer pesticides available
2. A wider range of BCAs
3. Better formulations, shelf-life, simplicity
4. Biofertilizers:
• N fixing – nodules and free-living
• Mobilization of P and micronutrients
• Buffering abiotic stress:
• Tolerance of heat, cold, drought, waterlogging, soil
toxins, toxic metals
5. Soluble silicon - a powerful tool to add

55. Potential Problems with BCA & BFZ
• Foreign strains, not well adapted to SA soils
• Many strains need to be screened to find one really
powerful strain – requires time, money and research
facilities
• Good BCA but poor formulation = ineffective
• Spores counts too low – 105 /g instead of 107 /g
• Contamination by other fungi
• It is not a chemical, but a living organism. Back seat
of a car for 4 hours will kill it.
• Relatively short-lived except spore-formers (Bacillus),
6-12 months

56. 56