Modern Biocontrol Agents and Biofertilizers

Prof. Mark Laing

Plant Pathology, UKZN & Plant Health Products (Pty) Ltd

Infected Ant

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

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

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

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

Biocontrol of Rhizoctonia on

cucumber seedlings

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

0

20

40

60

80

100

120

Untre

ated

Cru

izer o

nly

Eco

-T o

nly

Cru

izer +

Eco

-T

Tricho

Plus on

ly

Cru

izer +

Tric

hoPlus

avg

. ro

ot

weig

ht

Effects of treatments on root wet weight

A Maize Trial with 2 Trichodermas & Cruiser

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)

Kenyan Lisianthus with Fusarium oxysporum root rot

No treatment Trichoderma applied weekly

Survival (%)

0

20

40

60

80

100

Con

trol

Rhi

zoc

T d

r +

Rhi

zoc

T s

t +

Rhi

zoc

Treatment

Sur

viva

l (%

)

Total Dry Weight

0

2

4

6

8

10

Con

trol

Rhiz

oc

T d

r +

Rhiz

oc

T s

t +

Rhiz

oc

TreatmentDry

Weight

(g)

Biocontrol of Rhizoctonia on

cucumber seedlings

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.

A rust pustule colonized by S. filum

S. filum – black spore

capsules in the old rust

pustule

A new rust pustule

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

17

Rust

Spore

Rust Spore

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

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

Untreated Control

Yeast B13

Rice Weevil (Sitophilus oryzae) infected

with Beauvaria bassiana Rice Weevil (Sitophilus oryzae) infected

with Beauvaria bassiana

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

Beauveria bassiana parasitizing

army worm larvae

Beauveria-infected

white grub adult

Beauveria-infected

black vine weevil

Dead red spider mites after Eco-Bb x K silicate

on brinjal (Gatarahiya & Laing, 2008)

0

20

40

60

80

100

120

0 1 2Beauveria rate (g l-1)

% d

ead

mit

es

(ad

ult

s+

juven

iles)

No Si

With Si

Bollworm on Wheat Infected by Virus

Beetle grub filled with EPN’s

Pictures taken from the University of Florida extension service web-site

http://edis.ifas.ufl.edu/IN468

Entomopathogenic nematode entering an insect larva

EPN

Larva

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 !

Nematode attacked by a nematode-trapping fungus

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

No

Treatment

Trichoderma

Nutrient uptake can be enhanced by alterations to root structure

Untreated

1.8 area units

Eco-T seed treatment

3.2 area units

Eco-T treated maize root

numerous root hairs Untreated maize root

Few root hairs

Nutrient uptake is enhanced by increased number of root hairs

Root and shoot lengths of perenial

ryegrass (69 days)

0

50

100

150

200

250

Untr

eate

d

Tre

ate

d

Untr

eate

d

Tre

ate

dFeb planting March planting

Len

gth

(m

m)

Shoot

Root

Abiotic Stress: some Trichoderma

strains and beneficial soil bacteria buffer plants from extreme environmental conditions:

• Waterlogging

• Drought

• pH extremes

• Nutritional stress

• Pathogen / Environment interaction

Eco-T® buffers vs water-logging

Effects of soil moisture in lettuce (inoculated with Pythium)

0

100

200

300

400

500

600

700

800Y

ield

(g) w

et w

eigh

t

uninoculated controlinoculated control

biocontrol

Treatments

optimum irrigationhalf double

0

20

40

60

80

Mea

n w

et w

eigh

t (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)

40

60

80

100

120

140

160M

ean

tota

l wet

we

ight

s (g

)

control(u) control(i)

biocontrol

Treatments

pH4

pH5

pH6

pH7

Effect of pH on disease severity and biocontrol activity

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

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

Soybean –

Rhizobium nodules

(Strain WB74)

Red nodule =

fixing N

Green nodule =

parasite !

Effect of microbial treatments on Soybean yield

0

500

1000

1500

2000

2500

untre

ated

Eco

-T 1x

Eco

-T 2x

Rhiz

obium

Eco

-T +

Rhizo

bium

Treatments

Yie

ld (

g)

Series1

Rhizobium vs waterlogging stress in wattle

• 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

Figure Increased rooting in treated plants (left)

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

Typical Opal Phytoliths (maize & grass)

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

Cold Stress: bananas after 40C x 4 days

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

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