Northwest Michigan fruit regional report – May 6, 2014

Cool and wet weather is slowing spring throughout the Northwest region. Blooming fruit is not predicted in the next week.

Weather report

For many of us here in Northwest Michigan, spring does not seem like it will ever come. Cool and wet weather has become the norm, and the occasional sunny day comes as a bit of a surprise. Daytime highs have been in the mid-40s to low 50s degree Fahrenheit, and nighttime temperatures have been in the low 40s with exception of last night, May 5, where the temperatures were in the low 30s. However, these cool temperatures coupled with cold winds off of Lake Michigan make the temperatures seem much cooler.

We are slowly accumulating growing degree days (GDD), but we are considerably behind our 20-plus year average. So far in 2014, we have accumulated 117GDD base 42 and only 25GDD base 50 while our average accumulations are 272GDD base 42 and 119GDD base 50. This week’s temperatures are expected to be in the 60s and even reaching into the 70s on Wednesday and Thursday, May 7-8.

In addition to cool temperatures, we have had substantial rainfall. In April, we had almost 5 inches of rain at the Northwest Michigan Horticultural Research Center (NWMHRC), and in May we have had just over 0.5 inch in the past five days. Even if there has been no rain in the forecast, conditions have been gray and overcast. Soils are still wet in the orchard, and in some low spots we still have standing water.

Crop report

As to be expected with the cool temperatures, tree fruits and vines have not moved much from last week.

Due to continued cold temperatures, there has been no noticeable development in bud development in wine grapes.

We are starting to see some initial green in sweet and tart cherries. A little green is also starting to show up in Red Delicious apples, but development is slow with the current conditions. Growers continue to move forward with pruning, and most are saving sweet cherries until warmer and drier conditions to minimize the impacts of bacterial canker.

We have observed winter damage in young sweet cherries, and the cambium is noticeably brown when we cut into the wood. We will try to determine the extent of this damage in the coming weeks. Some growers to the south have sprayed or are considering applications for apple scab with green tissue on some early varieties and with the ongoing rainy conditions, but overall fungicide applications have been minimal.

Pest report

The NWMHRC is monitoring for apple scab spores during the primary infection period. With the exception of some earlier apple varieties starting to show green, most apple varieties remain dormant or silver and, as a result, are not yet susceptible to scab infection. However, apple scab spores were discharged during last week’s rain. Our first detection of spores was on April 30 following a rain event where spore numbers were an average of 50.75 spores per spore rod. Since the first detection, the average number of spores per rod has increased to an average of 258.75 per rod. This most recent spore count followed a wetting period that the NWMHRC Enviro-weather station recorded as beginning in the evening on April 30 and ending mid-day on May 3.

The cool weather this spring has delayed insect activity. Pheromone monitoring traps for spotted tentiform leafminer, oriental fruit moth and American plum borer were deployed at the NWMHRC on April 30. Since then, we have not detected any of these pests at the station. However, green fruit worm moths are active and were detected in our traps. These insects emerge early in the season and often fly earlier than other species. We have received more reports of San Jose scales on sweet cherries in Leelanau, Grand Traverse and Antrim counties.

Dormant oil sprays have been applied in both apples and cherries; Michigan State University Extension advises growers to be cautious when spraying oil if freezing temperatures are predicted because phytotoxicity can occur when oil is applied during cold temperatures. Some copper applications have also been made in apples in the last few days.

Dr. Rothwell’s work is funded in part by MSU’s AgBioResearch.

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