What makes a compost disease suppressive?

Allison L H JackDr. Eric B. Nelson’s Laboratory Group

Veg Expo 1-27-10

Disease suppression…What do we know?

• Single organism biological control is well understood in specific cases

• Suppression of disease by a complex community of microbes is much more complicated!

Example: Pythium spp. (damping off)

Post-emergence damping off

[www.ipmimages.org]

A. Jack Cornell University 2008

vegetative hyphae

sporangium

germinating sporangium

zoosporangium zoospores

antheridium

oogonium

oogonium oospore

Germinatingoospore

asexual

sexual

direct

indirect

DISEASE

[modified from Matthews 1931]

P. aphanidermatum

Mechanisms of biocontrol

• Single organism: – Antibiosis– Competition for nutrients– Parasitism– Induced systemic resistance

Antibiosis

Root surface Bacillus subtilis“Kodiak TM”

Zwittermicin A (antibiotic)

[Shang et al. 1999]

Pythium zoospore

Competition for nutrients

Seed exudates

Cucumber seed

Linoleic acid

Pythium sporangium

[van Dijk and Nelson 2000]

Enterobacter cloacae

Linoleic acid

Pythium sporangium

Induced Systemic Resistance (ISR)

Pseudomonas corrugata Pythium

sporangium

[Chen et al. 2000]

Parasitism

www.nysaes.cornell.edu/ent/biocontrol/pathogens/trichoderma

Multiple organism biocontrol

• Often associated with high microbial biomass and activity, but not always

• Unclear which organisms are involved and how they interact with each other and the pathogen

• Goal: – Understand how disease suppression works in a

single system so we can make the practice more effective

Effect of suppressive amendment on pathogen populations

decreasenullincrease

[Bonanomi et al 2010]

Mic

robi

olog

ical

Chem

ical

Enzy

mat

icSuppression Index (SI)

If negative: negative correlation between factor measured and suppression

If positive: positive correlation

If zero: neutral

[Bonanomi et al 2010]

Predictive factors vary by pathogen species

Thermophilic compost• Static aerated (indoor)• Windrows (outdoor)• 6-9 months curing• Relies primarily on action

of microbes

Vermicompost• Usually follows a hot

composting step• Worm beds (indoor)• Windrows (outdoor)• Entire process: ~70 days

What is vermicompost?

Vermicomposts can protect plants from disease

• Multiple cases documented in scientific literature

• But, suppression depends on:– Amendment rate– Type of feedstock– Temperature– Presence of synthetic fertilizers– Potting media substrate

Vermicompost is added to tops of plug trays, aerated vermicompost extract is piped directly into overhead irrigation

2008

Aerated compost extract

• Expensive equipment ($20,000)

• No shelf life• Additives needed

• Cheap equipment ($250)• Long shelf life• No additives needed

Non-aerated compost extract

sump

[Elzinga Hoeksema Nurseries, MI]

100 gallon tub

Timer

Sump pump(circulates 2x a day)

1:60 vermicompost: water ratio

Zoospore pre-infection events

Conclusions• Vermicomposts can be a valuable cultural

practice for suppressing plant disease • Scientific understanding is not yet at a level

where we can make predictions for specific composts and specific pathosystems

• Consider collaborating with regional researchers to further develop these practices

AcknowledgementsNelson Lab:Mary Ann KarpEric CarrMonica MinsonHillary DavisEllen CrockerSarah ArnoldDave Moody

My committee:Eric Nelson (PPPMB)Anthony Hay (MICRO)Anu Rangarajan (HORT)Kathie Hodge (PPPMB)Scott Peters (EDUC)

Financial support:

Department of Plant Pathology and Plant Microbe Biology

USDA BARD

Knight Institute for Writing in the Disciplines

New York Farm Viability Institute

NYSTAR Center for Advanced Technology & USDA SBIR Phase I & II (with Worm Power)

Organic Farming Research Foundation

Organic Crop Improvement Association

Andrew W. Mellon Fellowship

Kent Loeffler – photo credits

SBIR Program

Industry collaborator: Tom Herlihy Worm Power