Northwest Michigan fruit regional report – April 19, 2016
The recent warmup kick-started tree development, and apple scab could be a concern with rain predicted later this week.
Weather and crop report
Most of the trees at the Northwest Michigan Horticulture Research Center are showing some green tissue. Sweet and tart cherries are at the side green stage, and apples are at green tip to 0.25-inch green depending on variety. Tree development will likely slow toward the weekend with the predicted cool down. Growers are busy pruning, and there is a lot of brush still in the orchards.
We have accumulated 141 growing degree-days (GDD) base 42 and 60 GDD base 50. Our 20-plus year averages for this time are 127 GDD base 42 and 50 GDD base 50, so we are quite on “average” this year. Tart cherries are typically at full bloom around 360 GDD base 42, and sweet cherry full bloom is at 275 GDD base 42. Little damage has been reported or observed in tree fruits in northwest Michigan from the recent cold temperatures.
A few of the earliest wine grape varieties in the research vineyard are showing a little bud swell, mostly on canes close to the ground. The condition of the canes looks fairly good except for the extensive scaring of the periderm from the hail on Aug. 2, 2015. It will take some time to tell if the hail injury will result in poor bud break or the flagging of shoots later in the growing season. If you are still pruning and renewing with long canes, I suggest laying out four canes instead of two if you were in the areas hit by hail. Spur pruning will take out much of the hail- injured wood—select the best spurs without hail damage near the base.
There is still plenty of time for dormant treatments against powdery mildew.
Saskatoon bud development has progressed rapidly in some plantings, and we have about 50 percent of the fruit buds in the full green stage at the research center. Based on observations over the last few years, there usually will not be any significant pest insect activity until the white tip stage when aphids may appear. The 2016 pesticide recommendations for saskatoons are now available.
Recent warm weather has accelerated tree development and growers are beginning to apply delayed dormant applications for pests and diseases this week. Many apple varieties are showing green, and there is a chance for rain overnight on Wednesday, April 20, into Thursday that will likely trigger apple scab spore release. Growers that have green tissue present should apply a copper application to protect trees prior to this week’s rain. If an orchard had scab last season, it will be of utmost importance to protect trees during this 2016 primary scab season. There have been reports of early spore discharge in other parts of the state due to warm conditions in March. Additionally, the warm conditions in the last week have hastened maturation of the overwintering fungus. Hence, protecting green tissue early in this primary season will be crucial to prevent early scab infection. The Northwest Michigan Horticulture Research Center will be sampling for apple scab spore discharge for the duration of the primary scab season.
Now is a good time to scout for overwintering scale, particularly in orchards that have had lecanium or San Jose scale or symptoms of scale in previous seasons. Lecanium scale infestations have been located next to wood lots or areas with lots of maple trees. San Jose scale has been more problematic in sweet cherry in recent years, and light colored sweet cherries are particularly susceptible. Growers should also keep an eye out for overwintering European red mite eggs that have been reported in low numbers.
Green fruitworm began flying during the recent warm up; however, insect activity will likely slow down later in the week with predicted cooler temperatures. The Northwest Michigan Horticulture Research Center trap line is in place, and we will begin monitoring for early season tree fruit pests such as the American plum borer and oriental fruit moth. We have also observed many pollinators and other beneficial insects foraging in the field recently.