Xanthocast or Walnut Blight Forecast

The Northern Sacramento Valley Walnut Blight Forecast is a service provided by AgTelemetry Network.


The Walnut Blight Model was developed by Dr. James E. Adaskaveg U. C. Riverside: Management Guidelines/ID for Walnut Blight.



The Xanthocast index for walnut blight is a 7-day cumulative index based on temperature and leaf wetness. This 7 day cumulative?index will range from 0 to a maximum of 35. The experimental spray threshold is 6. Disease will appear 14 to 21 days later, if inoculum is present and sprays are not applied while risk is present.


Values are intended to be used as guidelines only. Irrigation, inoculum levels and cultural practices may change disease risk from field to field. Common sense should be combined with regular orchard scouting as guidelines, especially since this is an experimental model. Values are deemed reliable but not guaranteed.


Model and Data Collection usually spans the period of March 15 to May 30 of a crop year.


To begin using the model calculate your cumulative index from daily indexes starting at your terminal bud break, catkin emergence (earliest start point) or pistillate flower emergence (latest start point).


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