By Amy Irish-Brown and Phil Schwallier
Rain, rain, go away. Cool weather is slowing down tree development.
Crop development
Tree development has slowed considerably with the much cooler weather. Very little leaf or flower development has taken place over the last few days. Most apple varieties have bloom open, with only the very late developing cultivars still at pink. Sweet cherry and plum are now blooming with some of the early varieties beginning petal fall. Peaches are in full bloom.
Disease report
Heavy rainfall settled in the area in the late evening on April 29, and showers are still ongoing as I write this on the morning of May 2. This results in a heavy apple scab infection for the general Grand Rapids, Michigan, area. Rainfall totals for most areas were between 1.75 inches and 2.5 inches, and orchards are soggy. Ascospore discharge numbers were much lower than the last two rain events, with 1,245 spores per rod as of the afternoon of May 1. Full cover fungicide programs with protectants and systemic action are called for with follow-up sprays necessary as soon as you can get back in your blocks when the rain ends tonight.
The recent cooler weather will be less of a risk for powdery mildew.
There was a slight risk for fire blight blossom blight in early blooming varieties last week. With the much cooler weather the past four days, there is no risk of blossom blight and continues to be the case based on the forecast for the next several days.
Hopefully the cool, wet weather will move on soon and favorable weather for bee activity and pollination will move back in.