Grand Rapids, Mich., area tree fruit regional report – April 23, 2013
Apple development continues to be delayed in the west central region.
Growth stage update
Very little has changed in apple development from last week due to the cold weather. A little bit of green tissue started last week on the earliest varieties of apples on sites that are warmer, more protected, or on sandy soils. The majority of apples are still in silver tip.
The forecast is not for any really warm weather until the weekend (April 27-28), so this slow start to green tip will continue. For growing degree days base 42 for the Ridge, we are at 82 DD42 through this morning (April 23). Green tip in McIntosh could hold off until the end of the week with the cooler temperatures in the forecast. I expect we won’t get to 125 DD42 on the Ridge until Sunday, April 28 – that’s the normal average DD42 for first green in Macs according to Michigan State University Extension.
Apple scab update
I have had spore rods out for a week now and with the heavy rains last Thursday (April 18), I did not catch any spores. Other areas of Michigan – southwest and southeast Michigan – have reported spore catches in low numbers. In the 20-plus years I have been monitoring spore release for apple scab, I have only caught spores ahead of green tip in two years.
A few have asked if all the rain of late would release most of the spores and make for a shorter or easier scab season. The short answer is no. Mother Nature has this apple scab thing worked out and the initial spore release is usually timed pretty close to first green. Plus, the spores don’t all mature at once and are released over time, so we get six to eight weeks of primary scab to cover for every year. Applications of copper sprays in apples have begun in some blocks as deemed necessary if there is green tissue starting.