Northwest Michigan Fruit Regional Report - April 21, 2015
With the warm temperatures over the weekend, most tree fruits are showing some green tissue, but development will be slowed with the predicted cold.
As in most springs, northwest Michigan weather has been all over the board. Over the weekend, we had a welcome burst of warmth and sunshine, and the grass almost seemed to green up overnight. Unfortunately, the warm weather moved out on Sunday night (April 19) and has been replaced with temperatures in the mid-30s and low 40s. These cooler temperatures have been coupled with rain, snow and sleet. Conditions are not conducive for working in the orchards, but growers are still pruning and planting has begun in earnest over this past week. We have accumulated 134GDD base 42 and 49GDD base 50. Michigan State University Extension reports these accumulations are almost spot-on with our 20+ year averages: 141GDD base 42 and 56.5GDD base 50.
As mentioned above, the warm weather over the weekend moved along our tree fruit crops. There is green tissue out on apples and cherries, but development will be slowed by the predicted cold and wet weather this week.
We have been taking some cuttings here at the NWMHRC, and we have seen little damage to any of our crops. However, we have heard reports of winter damage to young sweet cherries and peaches. We will know more about the extent of damage in the coming weeks. Overnight temperatures are predicted to be below freezing for the next three nights this week. Based on work done in growth chambers, sweet cherries at the side green stage can take temperatures into the mid-20s with little damage. This research showed that a low of 23 degrees Farenheit will result in a 10 percent kill when sweet cherries are at side green. Similar damage was reported in tart cherries under these same temperatures and bud development. Temperatures are expected to be in the high-20s across the region, and if these predictions are correct, we will see little to no damage in sweets, tarts or apples.
Warm temperatures over the weekend progressed development on apples, and green tissue is present on McIntosh, Gala, Red Delicious, and Golden Delicious at the research station. Primary infection of apple scab has begun, and the Enviro-weather apple scab model is reporting ongoing potential infection periods throughout the region. If green tissue is present on scab sensitive varieties, this tissue should be protected from infection to prevent more serious secondary infection later in the season. The critical control timing for apple scab is during the primary infection period to prevent season-long challenges that can become costly if apple scab takes a foothold early in the season. Copper can reduce fire blight inoculum, and protect green tissue from scab infection.
This week’s cool and wet conditions favor bacterial canker development. Growers should avoid pruning during these conditions to prevent spreading the canker pathogen to pruning wounds. Conditions are predicted to be drier later this week, which would minimize canker infection. Copper can be phytotoxic on sweet cherries when green tissue is present, and growers should use caution if they are planning to use copper for bacterial canker. Copper resistance has been documented in Michigan sweet cherries, so copper applications will provide little to no control of bacterial canker in sweet cherry.
Scouting for European red mite eggs and overwintering San Jose scale is underway in the region. We have received reports that European red mite eggs are evident on sweet cherries whereas it has been more difficult to find overwintering San Jose scale. Cold winter conditions could have impacted survival of overwintering pests, however, we are not certain to what extent at this time.