By Amy Irish-Brown
Tree fruit development is waiting for warmer weather.
Not much has changed from my Michigan State University Extension report last week, other than we have had a great deal of rain and orchards have become soggy. According to MSU Enviro-weather, degree-day totals have not moved much. Tree development has not moved much either. A few blocks of Gingergolds and Zestar have some green tissue showing and these early blocks have been sprayed with a copper spray in the last few days, but overall very little apple acreage in the Grand Rapids, Michigan, area has been sprayed yet.
I expect this weekend will be a good time to get those first sprays on ahead of the warmup forecasted for April 9, 10 and 11. Once this wet, cold weather (snow is forecasted for April 6) moves out, it’s time to get started with your spray season. Copper sprays can be started at any time, but are best placed as close to green tip as possible to get the most longevity from this early scab and fire blight management tool.
As expected, primary apple scab spores are mature and ahead of green growth. I caught the first spores with the rain on Thursday, March 30, 2017. There were 11 spores per rod—not a significant amount—but they are early again like last year, so be ready to go with scab covers with the first warm rain and green tip. My monitoring site is a commercial block of semi-dwarf McIntosh that had a little scab last year. I can see lesions on the fallen leaves, so I am expecting some good numbers through the primary scab season from this site.