BlightCaster — Walnut Blight Risk Index

Weather data & forecasts by Weather Tools, Chico CA · UC walnut blight model (Adaskaveg et al.)

demo data

Weather station

7-day index (0–35)

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Spray threshold 6 · growers choose 4–6

Season total since Mar 15

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Approximates final % disease if unsprayed (errs high)

Latest station reading

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Model setting

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Wetness derived from RH / dew point / rain (no leaf-wetness sensor)

Forecast outlook

Projected from the Weather Tools hourly forecast — experimental. Each day shows the predicted daily index (0–5), forecast wet hours, and where the 7-day index would land if the forecast verifies.

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Spray log — click the days you sprayed

Tap the sun (☀) for a daytime spray (6 AM–6 PM) or the moon (☾) for a nighttime spray (6 PM–6 AM, recorded as the night of that date). Click again to remove a date. Logged sprays pause the risk index for 7 days.

Walnut acres you farm

7-day index

Rolling 7-day sum of daily indices. Hairline marks the spray threshold (6). Disease typically appears 14–21 days after an index rise.

Daily index

0–5 per day: wet hours in three temperature ranges (6–12, 12–17, 17–27 °C), the middle range weighted ×3.

Season accumulation

Cumulative index since season start; tracks expected disease incidence.

Data table

Date	Daily	7-day	Season	Risk	Wet h 6–12°	12–17°	17–27°	Readings

Recorded spraying — all BlightCaster growers

Acres treated per day, split into ☀ daytime and ☾ nighttime halves, across every grower who logs sprays here. Each grower's acreage is spread evenly over each consecutive run of spray days. Scroll sideways for the whole season.

About. BlightCaster is a revival of XanthoCast™, the University of California walnut blight forecasting model developed by J. E. Adaskaveg (UC Riverside) with R. Buchner and W. Olson (UC Cooperative Extension), S. Lindow (UC Berkeley) and FieldWise Inc., published in the California Walnut Board Walnut Research Reports (2000–2005). It accumulates hours of leaf wetness in three temperature ranges into a daily disease-risk index; a rolling 7-day index times protective bactericide sprays. This site recreates the model, driven by Weather Tools station observations; hourly leaf wetness is derived from rain, relative humidity and dew point.

Advisory only. Indices depend on sensor siting and the wetness derivation, and this rebuild is being validated. Confirm spray decisions with your PCA / farm advisor, and follow all label requirements.