We finally started to see some signs of spring over the weekend with good growing degree day accumulations.
Posted on April 15, 2014 by Bob Tritten, Michigan State University Extension
Weather
With warm temperatures over the weekend, April 12-13, we have finally started to see signs of growth in most of our fruit crops. Most growers had a four-fold increase in growing degree days (GDD) base 42 over the last week and an average of an eight-fold increase in GDD base 50 in the last week.
Strong straight line winds and hail were reported at many farms late in the day this past Saturday, April 12. The storms moved through the region quickly, leaving many farms without power and some growers reporting tree loss and minor amounts of trellis tipping or leaning. Most growers reporting hail had pea- to marble-size hail, covering the ground in a few minutes at some farms. There were a few reports of golf ball-size hail where bud loss on the westerly side of the tree was extensive. There is no time of the season that hail doesn’t cause some injury to fruit crops.
Spring quickly reverted back to wintery conditions on Monday night, April 14, with many Michigan State University Enviro-weather stations reporting low temperatures in the lower 20s. Two to 4 inches of snow was also reported by many fruit growers this morning (April 15). These low temperatures will not likely cause damage to fruit flower buds.
Our season is behind normal by about a week to 10 days, but with warm temperatures over the weekend it did catch up on itself a great deal. Soil moisture conditions are generally wet across the region with no planting or ground preparation taking place. Pruning continues at most farms. Brush chopping is taking place at most farms.
East Michigan GDD totals for March 1 to April 14, 2014
Tree fruit
Apples are at bud swell to mostly silver tip. No flower bud damage from extreme cold winter temperatures is expected in apples. There are no pest problems to report in any tree fruit crops.
Pears are at early bud swell. No flower bud damage from extreme cold winter temperatures is expected in pears, but a more accurate assessment will be possible at bud burst when whole orchards, rather than individual buds, can be assessed.
Peaches remain dormant to very early bud swell. It is hard to assess peach development at this time of the season this year as it is hard to distinguish between simple lack of bud development and winter injury. Peaches are one of the most cold tender tree fruits and flower bud loss is expected when temperatures fall below -10 degrees Fahrenheit. Most injury occurs between -13 and -16 F. Most growers have significant flower bud losses. However, peach trees can lose many flowers and still have a good crop. Many growers are taking a “wait and see” approach to crop loss.
Many twigs and scaffold branches are light tan in the cambium area; I am concerned about potential winter injury in these trees. It was so cold this winter at many farms that I anticipate damage even to tree trunks.
Sweet cherries are at early bud swell. As with peaches, I anticipate damage to flower buds due to cold winter temperatures.
Tart cherries are at green tip for a few varieties on early sites with most being at bud swell. Tart cherries mostly show less damage in the colder sites than sweets; generally one to two dead florets are seen in the flower cluster bud.
Plums are mostly dormant. I expect to see winter damage in Japanese plums with less expected in European plums as they are more cold hardy.
Small fruits
Strawberry leaves are just starting to emerge from the crown on early sites. I expect to see many more beginning to emerge with warmer temperatures predicted later this week. Straw mulch removal is expected to begin later this week at our most southern Michigan farms. Refer to a complete strawberry straw removal article that was published last week by Michigan State University Extension for more details.
Raspberries are at bud break for most varieties to green tip for early varieties. Canes of summer fruiting types have a significant amount of cambium browning, indicating potential winter injury. You can see this browning to the snow line at many farms. Fall raspberries should be mowed now.
Blueberry bud scales have cracked open. Initial bud assessments indicate damage to flower buds. The damage takes two forms: withered shoots tips that dried from subfreezing conditions and cold winds, and dead flowers in the flower cluster bud. I am seeing both types of damage. I am finding several dead florets per bud with many viable florets appearing undamaged. As with many fruit crops this spring, a more accurate assessment will be possible at bud burst when whole planting rather than individual buds can be assessed.
Grapes show no movement. There is little damage in Concords and winter damage to wine grapes varies greatly between varieties and different fruit sites.
This article was published by Michigan State University Extension. For more information, visit http://www.cnchemicals.com/. To contact an expert in your area, visit http://www.cnchemicals.com/, or call 888-MSUE4MI (888-678-3464).