Does drought alter the efficacy of the herbicides?
Yes! Standards have been adopted by the PA Bureau of Forestry and the PA Game Commission to cease spraying when the Palmer Drought Index drops below (-2) in any given area. The Palmer Drought Index is explained and can be monitored on the internet at: www.cpc.ncep.noaa.gov/products. Scroll down to and select: Palmer Drought Severity Index Graphic (current). Note that the vegetation within a stand in a given region may exhibit signs of drought stress which are more or less than that which is indicated by the Palmer Drought Severity Index. Therefore, it takes a trained and experienced eye to judge whether the prescribed herbicide application will achieve the desired effects when drought conditions threaten.
