Can rainfall be a useful predictor of epidemic risk across temporal and spatial scales? Emerson Del Ponte Discussions with: Adam Sparks, Nik Cunniffe, Larry Madden Collaboration: Kaique Alves, Gustavo Beruski

Epidemic risk context for this talk Fungal disease (inoculum not limited) Field crops ("large" scale) Weather is key predictor Risk → Fungicide use or planning

Agrios (2005) "Classical" disease (infection) risk model Relative humidity and T Dew Rainfall Leaf / Hour Field / Day LWD measured or estimated LWD

Which wetness-variable? What is the model-building approach? Data-driven or Concept-driven? Biological or technical reasons Are Data available/accurate for the Scale?

Several rainfall-based variables have been selected/used in disease risk models Together with other variables Rainfall duration in hours (continuous) Presence/absence (binary) Number of rain days (count) Daily total (continuous) Weekly total (continuous) Weekly rain events (count) Rain gauges Satellite Gridded data Model estimations

Dispersal Infection Cloud cover wet deposition Survival (build-up) moisture splash moisture splash Effects of rainfall on epidemics?

Soybean rust (SBR) in Brazil Data-driven model - natural field epidemics Only rainfall (30-day after detection) explained variation in final disease severity Del et (2006)

SBR epidemics and rainfall Frequency and amount of rainfall during the epidemics

Three Uses of the SBR Rainfall Model 1) Risk analysis 2) Warning system 3) Early-season risk SEV = -2.14 + 0.18CR30 + 1.28RD30 Historical rain (day) Maximum Risk Region Real-time rain (day) More likely Risk Field Real time/forecast rain Likely Risk Large region Cumulative rain n. of Rain Days

1) Risk analysis Del Ponte et al (2011) How frequent severe epidemics? When during the season? Are they influenced by ENSO?

1) Risk analysis Risk of SEV > 70% 1 in 3-4 years 30 years daily rainfall (1979 to 2009) 30 disease onset dates > Jan 1st 24 locations

ENSO effects Warm Warm = El Niño Cold = La Niña

Time and space ENSO effects

Was the model/result too wrong? Warm Warm Cold Cold Warm Cold

Warning system Site-specific risk advisory system Daily severity values and action thresholds SEV15 = -2.14 + 0.18CR15 + 1.28RD15 15A 15B DSV SEV15A x 0.3 + SEV15B x 0.7 3-day mean daily severity value

Rainfall warning system Site-specific risk advisory system DSV50 action threshold - more conservative DSV80 action threshold - less conservative

Number of sprays (9 trials - 3 locations, Gustavo Beruski PhD Dissertation at Esalq) 4.6 4.0 2.6 4.8 5.3

Yield gains from using the systems (9 trials - 3 locations, Gustavo Beruski PhD Dissertation at Esalq)

Is it worth not follow calendar? Fungicide efficacy (%)

3) Early Season Risk (regional) PR RS Database: first report of soybean rust in commercial fields of a municipality Source: Consórcio Antiferrugem

2014/15 2015/16

2014/15 2015/16

Nov 2015 Rainfall These Rainfall data were obtained from the NASA Langley Research Center POWER Project funded through the NASA Earth Science Directorate Applied Science Program Nov 2014 Rainfall

These Rainfall data were obtained from the NASA Langley Research Center POWER Project funded through the NASA Earth Science Directorate Applied Science Program Nov 2015 Rainfall Nov 2014 Rainfall

These Rainfall data were obtained from the NASA Langley Research Center POWER Project funded through the NASA Earth Science Directorate Applied Science Program Nov 2016 Rainfall Nov 2017 Rainfall

http://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php What happened in 2015? El Niño! ENSO predictions for OND 2018

Past 30-day observed rainfall 7-day forecast rainfall Favorability risk maps

So, can rain be useful? Yes! for some diseases and crop production situations, is a very important weather variable driving epidemics from field to regional scales Tha y ! @edelponte