Predict Rice Sheath Blight Intensity

A helper function to provide sensible defaults for a dynamic mechanistic simulation of sheath blight disease of rice, causal agent Rhizoctonia solani AG1-1A Kühn. The model is driven by daily weather data, which can easily be accessed using get_wth to download weather data from NASA POWER.

Usage

sheath_blight(wth, emergence, ...)

sb(wth, emergence, ...)

Arguments

wth

Weather data with a daily time-step, normally NASA POWER data from get_wth, but any base::data.frame object that has been formatted using format_wth will have the following properly named columns and will work.

Field Name	Value
YYYYMMDD	Date as Year Month Day (ISO8601)
DOY	Consecutive day of year, commonly called "Julian date"
TEMP	Mean daily temperature (°C)
RHUM	Mean daily relative humidity (%)
RAIN	Mean daily rainfall (mm)
TMIN	Optional Minimum daily temperature (°C), see TMIN/TMAX Details
TMAX	Optional Maximum daily temperature (°C), see TMIN/TMAX Details
LAT	Optional latitude of weather observation, see LAT/LON Details
LON	Optional longitude of weather observation, see LAT/LON Details

emergence

Expected date of crop emergence

...

Additional arguments passed to seir.

Value

A data.table::data.table of disease intensity and infection sites. See seir for a full description of the column values.

Details

The model represents site size as 1 rice plant's tiller.

Default values for this disease model are derived from Table 2 (Savary et al. 2012).

sb is a shorthand alias for sheath_blight.

Note

Adapted from cropsim package version 0.2.0-5 by Adam H. Sparks, Department of Primary Industries and Regional Development, WA, AU. Original model development: Serge Savary & Rene Pangga (IRRI). Original R implementation by Robert J. Hijmans, Rene Pangga, & Jorrel Aunario (IRRI).

If the wth object provides LAT and LON columns, these will be included in the output for mapping purposes. Both values must be present. These columns are provided by default when using get_wth.

TMIN/TMAX Details

If simple_wetness is set to FALSE, the function will use the TMIN and TMAXcolumns in thewthobject to calculate the leaf wetness value for 24 hours of the day using therhlimandrainlimvalues and then usesRcWto calculate a value between 0 and 1 for the whole day. Whensimple_wetnessis set toTRUE, the function only sets the leaf wetness to 0 or 1 for the day based on the rhlimandrainlim` values.

LAT/LON Details

If the wth object provides LAT and LON columns, these will be included in the output for mapping purposes. Both values must be present. These columns are provided by default when using get_wth().

References

Castilla, N.P., Leano, R.M., Elazegui, F.A., Teng, P.S., Savary, S., 1996. Effects of plant contacts, inoculation pattern, leaf wetness regime, and nitrogen supply on inoculum efficiency in rice sheath blight. Journal of Phytopathology 144:187-192.

Gross, M.K., Santini, J.B., Tikhonova, I. and Latin, R. 1998. The influence of temperature and leaf wetness duration on infection of perennial ryegrass by Rhizoctonia solani. Plant Disease 82:1012-1016. doi:10.1094/PDIS.1998.82.9.1012 .

Hashiba, T. and Ijiri, T., 1989. Estimation of yield loss and computerized forecasting system (BLIGHTAS) for rice sheath blight disease. International Symposium on Tropical Agricultural Research: Crop losses due to disease outbreaks in the tropics and countermeasures. Tropical Agricultural Research Series (Japan) No. 22 pp. 163-171.

Savary, S., Willocquet, L., Teng, P.S., 1997. Modelling sheath blight epidemics on rice tillers. Agricultural Systems 55:359-384. doi:10.1016/S0308-521X(97)00014-0 .

Savary, S., Castilla, N.P., Willocquet, L. 2001. Analysis of the spatio- temporal structure of rice sheath blight epidemics in a farmer's field. Plant Pathology 50:53-68. doi:10.1046/j.1365-3059.2001.00531.x .

Savary, S., Nelson, A., Willocquet, L., Pangga, I., and Aunario, J. Modeling and mapping potential epidemics of rice diseases globally. Crop Protection, Volume 34, 2012, Pages 6-17, ISSN 0261-2194 doi:10.1016/j.cropro.2011.11.009 .

Sharma, N.R., Teng, P.S., Olivares, F.M., 1990. Effect of rice growth stage on sheath blight (ShB) development and yield loss. International Rice Research Newsletter 15:19-20.

Tu, C.C., Chang, Y.C., Wang, C.W., 1979. Studies on the ecology of Rhizoctonia solani, the causal organism of rice sheath blight. National Science Council Monthly, ROC 7:1208-1219.

See also

seir

Other helper functions: bacterial_blight(), brown_spot(), leaf_blast(), modified_kim_leaf_blast(), modified_kim_sheath_blight(), tungro()

Author

Serge Savary, Ireneo Pangga, Robert Hijmans, Jorrel Khalil Aunario, and Adam H. Sparks

Examples

# get weather for IRRI Zeigler Experiment Station in wet season 2000
wth <- get_wth(
  lonlat = c(121.25562, 14.6774),
  dates = c("2000-06-30", "2000-12-31")
)
#> No encoding supplied: defaulting to UTF-8.
#> No encoding supplied: defaulting to UTF-8.
sb_sim <- sheath_blight(wth, emergence = "2000-07-01")
plot(x = sb_sim$dates, y = sb_sim$intensity, type = "l")

# use shorthand function
sb <- sb(wth, emergence = "2000-07-01")
plot(x = sb$dates, y = sb$intensity, type = "l")