Treatment of rhizosphaera needle cast
We have read that we could treat the needle cast with chlorothalonil but also read that the 1st treatment should be around Memorial Day. Is it too late already to treat this year? Our reading indicated that treating too late in the year is a waste of money. Also, does the entire tree need to be sprayed or just the branches that look to be infected? We have at least 40 full-grown blue spruce in our yard so we're looking at a very big job!
Yes, it is too late. Timing is critical on the treatment as is sanitation. Please read the information from Iowa State: http://www.ipm.iastate.edu/ipm/info/plant-diseases/rhizosphaera-needle-cast