nanaamuah/fallarmy_worm_phenology

Temperature-driven fall armyworm phenology across Ghana using ERA5-Land, published thermal-development parameters, sensitivity analysis, and district-level scouting calendars. # Fall armyworm thermal phenology across Ghana, 1991–2025 How many generations Ghana's temperature record supports, where, and how much of the answer is a choice of citation. Rendered report: `report.qmd` ## Read this first This is a thermal accumulation model, not a population model. It says how many generations the temperature record could support if temperature were the only constraint. It does not know about host availability, rainfall, natural enemies, insecticide use, migration between regions, or the fact that fall armyworm in West Africa moves. It therefore produces an upper bound on generation number, not a forecast of abundance or damage. The thermal parameters come from controlled-temperature laboratory studies on particular populations. Field populations experience fluctuating temperatures, the microclimate inside a maize whorl differs from a screen-height reanalysis grid cell, and a population's thermal biology can vary geographically. The temperature driver is ERA5-Land reanalysis at roughly 11 km, which is a model output constrained by observations and not a measurement, and Ghana's station density in the early part of the record is low. The single-sine degree-day method is itself an approximation to a daily temperature curve. The sensitivity analysis quantifies uncertainty in the parameters only. It says nothing about whether the degree-day framework is the right model. The scouting calendar is an illustration of how such a model would be used. It is not extension advice. ## What is in here Two published thermal-development parameter sets for *Spodoptera frugiperda* are driven with 35 years of ERA5-Land daily temperature, aggregated to 258 Ghanaian districts. The pipeline returns a district map of mean annual generations, a companion map of how far that number moves when the parameter set is swapped, a Mann-Kendall trend over 1991 to 2025, and a scouting calendar by agro-ecological zone. The headline result is the gap between the two parame …