Grand Rapids area tree fruit update
Fruit farms are drying out nicely this week, but staying cool.
Tree fruit growth stages
Degree day totals are 10 days behind normal averages and tree growth is slowed due to cold air and soil temperatures. Apple growth is from half inch green to tight cluster depending on variety and site. We are noticing a few “false” flower buds in some apple varieties. These buds appear large and plump like a flower bud, but when they open, there are only leaves present. This is most likely related to the weather from summer of 2010.
Tree fruit pests
Apple scab. Last week was cool and wet and resulted in one long, heavy apple scab infection period. Most areas had well over 55 hours of wetting at 45 to 47 degrees. Rainfall totals were heavy and ranged from 2 to 4 inches. A line of storms moved through the Belding area the evening of April 26 and brought some hail to that area. It was difficult to keep good cover sprays on during this period. Spore discharge was the highest so far this season with 66 spores caught on April 26 and 155 spores when checked the afternoon of April 27. Scab symptoms from this event could show up around May 12. Lesions from earlier scab infections in the region are slated to show up between May 8 and 10 depending on the weather station area.
Powdery mildew. In blocks with problems in 2010 from mildew, control materials should be added earlier to the tank for tight cluster covers.
Insect development is still slow. There have been a few spotted leafminers flying in the warmer evenings as well as green fruitworm, but not insects of great concern yet.
On a side note, native stinkbugs are out and active and might be easily confused as brown marmorated stinkbug. Be sure to double check your ID with a picture reference.