January
2, 2012, by Dr. Xianming
Chen, USDA ARS, Pullman, Washington
Based on the 2011 December temperatures, stripe rust
yield loss on highly susceptible winter wheat cultivars is predicted to be
47%. The value is calculated using the
formula Y (yield loss) = 84.3 – 0.323X, where X is the absolute value of the
accumulated value of negative degree days based on daily maximum temperatures.The negative degree day value for a day equals
the maximum temperature (oC) subtracted by 7 (oC).
This is the first of a series of models we use
to predict stripe rust damage on susceptible cultivars for the major wheat
growing region in the Pacific Northwest.
For more information about this formula and other formulas, you may
refer to our recent publication (Sharma-Poudyal,
D., and Chen, X. M. 2011. Models
for predicting potential yield loss of wheat caused by stripe rust in the US
Pacific Northwest. Phytopathology 101:544-554).
If we classify stripe rust yield losses into four
categories, low (equal to or less than 20%), moderate (more than 20% but equal
to or less than 40%), severe (more than 40% but equal to or less than 60%), and
extremely severe (more than 60%), the predicted level of 47% for 2012 indicates
a severe level, higher than normal (35%).
For comparison, the 2010 stripe rust epidemic caused 60% yield loss and
the 2011 caused more than 90% on highly susceptible winter wheat cultivars.
