pest problems that can be brought into a field in or on

Kenneth Frost, Assistant Professor and Extension Plant Pathologist

Hermiston Agricultural Research and Extension Center

WA/OR Potato Conference, Kennewick, WA,

January 23, 2020

Pest problems that can be brought into a field in or on seed tubers and which ones to worry about most

Plant Pathology, Volume: 65, Issue: 1, Pages: 3-16.

Potato Pest Management Starts with Seed

Potato pests: eukaryotesLate Blight

Rhizoctonia canker

Early Blight

Weeds

Nematodes

Potato Virus Y

Bacterial Ring Rot

Potato pests: bacteria

Blackleg

Soft Rot

Purple top

Zebra chip

Photo by C. Miller

Potato pests: viruses

Calico

Potato leaf roll virus

Potato Virus Y

Plant Pathology, Volume: 65, Issue: 1, Pages: 3-16, First

published: 28 July 2015, DOI: (10.1111/ppa.12439)

How do you determine which pests are most important to your farm?

1) Rely on expert opinion

Pathogens/diseases mentioned (in order of appearance):

1. Potato virus Y

2. Bacterial ring rot

3. Late blight

4. Potato leaf roll virus

5. Tobacco rattle virus (Stubby root nematodes)

6. Potato mop-top virus (Powdery scab)

7. Tuber soft rots

Expert Opinion

Pathogens/diseases mentioned (in order of appearance):

1. Potato virus Y

2. Bacterial ring rot

3. Late blight

4. Potato leaf roll virus

5. Tobacco rattle virus (Stubby root nematodes)

6. Potato mop-top virus (Powdery scab)

7. Tuber soft rots

Expert Opinion

TRV

BRR

PVY

Soft Rot

PMTV

Late Blight

How to determine which pests you should worry about bring onto your farm

1) Rely on expert opinionHow do experts identify the problem pests?

Combine:Historical data and knowledgeInformation of pest biology

Make a prediction about which pests are likely to be problematic

Frost et al. 2013. Plant Disease 97(10):1268-1280.

Seed certification systems work and provide historical data

Ring rot (caused by Clavibacter michiganensis) has, for the most part, been held at bay

Potato spindle tuber viroid (PSTVd) (until very recently) had essentially disappeared

PLRV is very rare in part due to seed certification but also likely due to the introduction and widespread use of systemic neonicotiniodinsecticides in potato production

What are the next problematic pathogens?

1970 1980 1990 2000 2010

PSTVd

Bacterial Ring Rot

PVYN

PVYNTN, PVYN:O, Other recombinants

Brown rot

Potato mop top

Potato cyst nematodes

2020

Corky ringspot (Tobacco rattle virus)

PLRV

?Soilborne pathogens

Soilborne pathogens

How to determine which pests you should worry about bringing onto your farm

1) Rely on expert opinion

2)Conduct a risk assessment

Risk analysis

Risk: a hazard and the magnitude of its consequences

Hazard: Likelihood of a condition, event, or circumstance

(e.g., introduction of a pathogen to your farm)

Risk = hazard x exposure (or consequences)

Risk analysis – a systematic way of gathering,

evaluating, and recording information leading to

recommendations for an action in response to an

identified hazard

Steps to conduct a risk assessment for your farm

1. Identify the risk that is to be analyzed and potentially controlled (i.e. hazard and its consequences, can be done for each individual pathogen)

2. Develop a qualitative description of the risk (e.g., what might happen, why, factors that affect the risk, etc.)

3. Develop a semi-quantitative or quantitative analysis of the risk and associated risk management options

4. Implement a risk management strategy

Are management options available for each pathogen?

• Yes (easily controlled), Yes (difficult to control), No

Economic considerations• Yield loss or cost-to-control in

the short-term• Yield loss or cost-to-control in

the long-term

Can pathogen be eliminated from farm after establishment?

• Yes or No

Pathogen presence in or on seed

• Ubiquitous pathogen

• Known to be present in the region where your seed was grown

• Documented on North American Certified Seed Potato Health Certificate

Hazard X Consequences

For phytosanitary issues, most attention is focused on affecting the likelihood – it is best to reduce the likelihood of the introduction

If possible, don’t introduce a pathogen to your farm!!!

An on-farm risk analysis can consider all consequences (i.e., crop loss as a function of time, mitigating costs as a function of time)

Consequences

Ha

zard

Pa

tho

gen

in

tro

du

ctio

n t

o y

ou

r fa

rmFor each pathogen

Pathogen or Disease In seed

Management optionsavailable

Can be eradicated after introduction

Profit Loss(short-term)

Cost-to-control (short-term)

Profit Loss(long-term)

Cost-to-control(long-term)

PVY Common M Y Low Low Low Mod

BRR Rare N Y High High Low Mod

PMTV (Powderyscab)

Unknown(unknown)

N N Mod Low High High

Hazard X Consequences

Developing pest risk assessment- Start with qualitative information- move towards quantitative information










PMTV (Powderyscab)

Unknown(unknown)


Hazard (% of seed lots with the pathogen)

Pathogen 2017 2018 2019PVY 42.5 44.4 43.4BRR 0.0 0.0 0.0PMTV 0.0 0.0 5.3

Other pathogens in or on seed

(% of seed lots with the pathogen)

Pathogen 2017 2018 2019PVY 42.5 44.4 43.4BRR 0.0 0.0 0.0PMTV 0.0 0.0 5.3TRV 0.0 0.0 0.0V. dahlaie - 40.6 52.2C. coccodes - 18.8 40.3Pythium (+res) - 0.0 1.5










PMTV (Powderyscab)

0.05 N N Mod Low High High

Consequences

PMTV SOS (%) % Sym (EOS) % EOSSL1 100 0 foliar (0 tuber) 40SL2 50 0 foliar (0 tuber) 20SL3 75 0 foliar (0 tuber) 10SL4 100 0 foliar (0 tuber) 60





Cost-to-control(short-term)



PVY 0.43 3 0 0 0 0 2

BRR 0.005 4 3 4 4 0 1

Late blight 0.01 1 0 3 4 0 1

PLRV 0.01 1 0 1 0 0 0

TRV (stubby root nematode)

0.03 2 6 4 4 2 4

PMTV (Powderyscab)

0.05 4 12 2 0 4 4

Tuber soft rots 0.10 4 0 1 0 1 1

Quantitative assessment

RankPathogen or Disease

In seed(Hazard)

Consequences(Exposure) Risk

1 PVY 0.43 5 2.2

2PMTV (Powdery scab)

0.05 26 1.3

3 Tuber soft rots 0.10 7 0.7

4TRV (stubby root nematode)

0.03 22 0.7

5 Late blight 0.01 9 0.1

6 BRR 0.005 16 0.1

7 PLRV 0.01 2 0.0

What to Notice

Risk is largely driven by the hazard – if the introduction occurs regularly then there are regular consequences(i.e., PVY likely has consequences in every year)

Some low likelihood hazards that have very high cost or long-term consequences may also result in high risk (i.e. introduction of PMTV)

RankPathogen or Disease

In seed(Hazard)

Consequences(Exposure) Risk

1 PVY 0.43 5 2.2

2PMTV (Powdery scab)

0.05 26 1.3

3 Tuber soft rots 0.10 7 0.7

4TRV (stubby root nematode)

0.03 22 0.7

5 Late blight 0.01 9 0.1

6 BRR 0.005 16 0.1

7 PLRV 0.01 2 0.0

Hazard values are just estimates

Seed lot data (and other historical data) can inform real estimates of the hazard

Exposure estimates are made up

You may have better data to estimate the consequences (i.e. short and long-term) of introducing an individual pathogenThese can also depend on markets and trade issues

This example:

Develop and Implement a risk management strategy

Make rules and follow them –e.g.

Rule #1 - Inspect seed potato health certificate and use any other information you can get your hands on

Rule #2 - Do not purchase seed with known <insert pathogen> pathogen ever

Rule #3 - Seed with known x pathogen can be planted in fields x, y, or z, but not in other fields on the farm

Take Home Message

The human gut is bad at risk assessment

A formal risk-assessment can help to evaluate risk in a way that is specific to your operation

When in doubt, don’t introduce a pathogen to your farm!!!

Be proactive about seed health and seed you bring onto the farm

Acknowledgements

OSU HAREC Plant PathologyHannah RivedalVictoria SkillmanCassandra FunkeXiaoping LiDylan Enright

Funding SourcesOSU-Ag. Research FoundationNorthwest Potato Research ConsortiumOregon Potato Commission

USDA-ARS State Partnership ProgramUSDA-SCRIUSDA-AFRIUSDA-APHIS

Oregon State University, Dept. of Botany and Plant Pathology

Questions?





Cost-to-control(short-term)





Late blight Mod M Y Mod High Low Mod

PLRV Rare Y Y Mod Low Low Low

TRV (stubby root nematode)

Unknown(unknown)

Y M High High Mod High

PMTV (Powderyscab)

Unknown(unknown)


Tuber soft rots Common N Y Mod Low Low Mod

Qualitative assessment

Seed potato health certificates provide key information on seed health

Is a North American Certified Seed Potato Health Certificate available for the seed you are purchasing?

pest problems that can be brought into a field in or on

Documents