Grand Rapids, Mich., area tree fruit regional report – April 30, 2013
Tree growth is off to a low start in the west central region, but it has begun.
Growth stage update
Finally some warmer weather has moved in for a few days and that’s spurring on fruit tree growth. We officially reached green tip on McIntosh on Saturday, April 27. Ironically, that’s the same date in 2012 that the first hard freeze moved in and took out much of our tree fruit crops out. With high temperatures near 80 degrees predicted for this week, tree growth will move rather quickly, especially with the warm rain this morning, April 30.
Growing degree day totals are approximately two weeks behind normal averages, but we will lose some of that deficiency with the warmer weather. Degree totals through midnight April 29 for the Sparta Enviro-weather station are 147 base 42 and 50 base 50.
Apple scab update
I have had spore rods out since April 16. Spores were caught in light numbers with rains on April 23 and April 25. Green tip in McIntosh started on April 27, so we are now at risk for primary apple scab infections for green tissue. The rain today, April 30, is still several hours short of being an infection period and it appears to be drying off quickly, so it is likely it will not become an infection. Eight hours of dry time – no leaf wetness and relative humidity below 90 percent – are needed to end a wetting period.
You can visit the Enviro-weather website for hourly updates of current disease situations for tree fruits. It does take about 15 minutes after the top of the hour for our system to retrieve data from the weather stations – I like to check it on the half-hour for the latest information.
There is rain in the forecast for just about every day this week. With potentially fast leaf development and possible scab infections, good coverage of fungicides will be important this week.
Even in problem blocks there should be little to no risk for fire blight infections this time of year. A few people have been asking about this as they are finishing up pruning and the rain this morning had some pea-sized hail in it in some areas. Early season copper sprays help to sterilize tree surfaces of any fire blight bacteria. Michigan State University Extension recommends saving your antibiotic sprays for bloom.
There is very little activity in the insect world. Green fruitworm adults are flying. Spotted tentiform leafminer adult flight should also begin any day. Scouts should be watching for overwintering obliquebanded leafroller larvae in apple terminals, especially in 2012 problem blocks. European red mite egg hatch is several weeks away, but there are some early season control options that should be applied soon to target eggs.