Climate and the risk of pests and disease

Primary research activities in this area:

1. Participatory evaluations of risk for potato tuber moth and Andean potato weevil in relation to climate parameters in the Altiplano

2. Evaluation of climate and the utility of crop diversification for disease management

3. Integrated predictions of future risk for potato tuber moth and potato late blight based on climate change predictions

Climate and the risk of pests and disease

Primary research activities in this area:

1. Participatory evaluations of risk for potato tuber moth and Andean potato weevil in relation to climate parameters in the Altiplano

2. Evaluation of climate and the utility of crop diversification for disease management

3. Integrated predictions of future risk for potato tuber moth and potato late blight based on climate change predictions

From the LTRA-4 participatory community assessment:

Farmers in our study area of the Bolivian altiplano perceive pest problems to be increasing, along with increasing resistance to pesticides

They identified potato tuber moth and Andean potato weevil as priority constraints to production

Objectives:

Estimate Andean potato weevil and potato tuber moth risk in three communities in each of Umala and Ancoraimes, Bolivia (expanding to Puno, Peru)

Link pest risk with climate and socioeconomic factors

Methods:

Measure pest populations in a study field in each of three communities in each of two regions across three years

Use a ‘windows’ approach to evaluate time intervals that impact pest population growth in the field

Evaluate the relationship between risk and climate variables across years using the site-year combinations as replicates

Pitfall traps used for sampling Andean potato weevil

Pheromone traps used for sampling potato tuber moth

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Semanas

Nº d

e ad

ulto

s

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13

28

Tem

p. M

áx. y

m

ín.

Premnotrypes sp Rigopsidius piercei Tº máx Tº mín

Example data set from one community: Andean potato weevil 2006-2007 in the community Jatuquira: Number of adults of two species with maximum temperature and minimum temperature

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Vinto Coopani Jatuquira San Jose de Llanga

Premnotrypes spp Rhigopsidius piercei

Andean potato weevil 2006-2007 in three communities in Umala: The average number of adults retrieved from traps

Climate and pest populations

As we gather more site-year observations and compare summary statistics, we are populating this figure for different combinations of climate statistics

Associated socioeconomic and management data will provide context

Climate summary statistic for one season

Pop

ulat

ion

for

one

seas

on

Each point indicates the result from one community in one season

Climate and the risk of pests and disease

Primary research activities in this area:

1. Participatory evaluations of risk for potato tuber moth and Andean potato weevil in relation to climate parameters in the Altiplano

2. Evaluation of climate and the utility of crop diversification for disease management

3. Integrated predictions of future risk for potato tuber moth and potato late blight based on climate change predictions

Reg

iona

l ino

culu

mlo

ad

Year-round host availability

Short season of host availability

Time through year

Dry season

Host available

Reg

iona

l ino

culu

mlo

ad

Year-round host availability

Short season of host availability

Time through year

Dry season

Host available

How does season length influence disease risk?

Analysis in collaboration with the International Potato Center

Garrett et al., in revision for Ecological Applications

Use of potato cultivar mixtures can reduce the risk of potato late blight

Garrett and Mundt 2000

Time

What is the effect of season length on the utility of potato mixtures to manage disease?

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Predicted regional inoculum load (increasing)

RM

R

Corvallis HuancayoLa Niña

HuancayoEl Niño

CajamarcaLa Niña

CajamarcaEl Niño

Quito

Increasing season length

RMR <1 indicates a benefit from mixtures

Garrett et al., in revision

Climate and the risk of pests and disease

Primary research activities in this area:

1. Participatory evaluations of risk for potato tuber moth and Andean potato weevil in relation to climate parameters in the Altiplano

2. Evaluation of climate and the utility of crop diversification for disease management

3. Integrated predictions of future risk for potato tuber moth and potato late blight based on climate change predictions

Estimates of potato late blight risk in the altiplano

1995-1998: No disease predicted

2001-2004: …

We are using GIS to map risk predicted from disease and pest risk forecasting models

There are also models of weather effects on potato tuber moth that we will draw on for modeling that system

Estimates of disease and pest risk in the altiplano

We are developing risk maps for late blight under climate change scenarios based on existing models of the relationship between climate variables and epidemiology

Sporleder et al. 2004

Potato tuber moth response to temperature in controlled environment experiments:

Development rates for larvae and pupae

Developing a conceptual framework for the impacts of global change on cropping system constraints...

to guide strategies...

An early version of assessment of biological relationships follows– this might function as one component of a more complete model– even limited to biology, there are interactions across all scales

Garrett et al. 2006

Garrett et al. 2006

Evaluation of thresholds, interactions, and positive feedback loops

A small change in temperature or precipitation does not necessarily imply a small change in disease risk

Examples from epidemics follow

Also need to consider interactions between changes in disease and pest risk and human capabilities for management

Garrett 2008

The local inoculum load builds during the period of conducive weather

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Month 1 Month 2 Month 3 Month 4 Month 5 Month 6 Month 7Per

cent

age

inoc

ulum

sat

urat

ion

Because plant disease pressure often increases following a compound interest model, increasing the length of the growing season slightly can have a very large impact on inoculum load

An Allee effect may produce thresholds for pathogen reproduction

(Allee effect = lower per capita reproduction in small populations)

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Per

cap

ita r

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Allee thresholds may produce larger impacts from climate shifts than would be anticipated with partial knowledge

Garrett and Bowden 2002

Pathogen population size

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Feedback loops for disease management

Management based on controlling local inoculum production becomes less useful as regional inoculum loads rise

•Field sanitation•Intercropping and mixtures•Resistance based on lower inoculum productionU

tility

of

loca

l man

agem

ent

Regional inoculum load

Responding to climate changeWe are developing an integrated framework for evaluating

responses to climate change for any given disease or pest

Characterization of resources and needs in areas such as the following, at all relevant scales:

-Plant genetic resources for resistance and issues for their deployment

-Producer knowledge and resources, and training systems

-Historic and predicted population characteristics for pathogens, vectors, and biocontrol agents

-Historic and predicted climate characteristics

-The nature of interactions between these areas

Then: Validating the conceptual model