Southeast Michigan fruit regional report – May 5, 2015

Warmer temperatures last week brought stone fruits into bloom, soon to be followed by apples, pears and blueberries. Soils remains very dry across most of east Michigan.


What a difference a week with warmer temperatures has made in the rapid development of flowering of our fruit crops. We have accumulated a good number of growing degree days (GDD) in the last week, with some Michigan State University Enviro-weather stations doubling their GDD base 50 totals. Our season is running back toward normal for both GDD totals and flowering stages.

Soils remain unusually dry across the region for this time of spring. Most fruit growers are watering newly planted tree and small fruits and others are getting equipment ready to begin watering established fruit plantings in the next week if we do not get significant rain events. About a half-inch of rain is predicted from today’s showers, May 5.

East Michigan GDD totals for March 1 to May 4, 2015





Commerce (Oakland)




Emmett (St Clair)




Flint (Genesee)




Lapeer (Lapeer)




Petersburg (Monroe)




Pigeon (Huron)




Romeo (Macomb)




Tree fruits

Apples are mostly at first pink with early flowering varieties at full pink to early king bloom. With another day of warm temperatures, I expect to see bloom in most apple varieties as things will move quickly the way this season is unfolding. With bloom in apples expected Thursday or Friday, May 7-8, as well as warm to hot conditions and rain predicted, fire blight prevention and control will be at the top of apple grower’s minds. The fire blight (Maryblyt) model in Enviro-weather has EIP predictions of over 100 for all areas for late this week.

Apple scab also will remain a concern for later this week. While we did have a wetting event yesterday, it did not result in an infection period. Apple scab spore discharge continues to rise with each of these wetting events with an average of 129 spores per rod collected in yesterday’s rain.

Insect activity has started to pick up with warmer temperatures. High trap catch of spotted tentiform leafminer adults occurred in the last few days, as has been the case for redbanded leafrollers. Oriental fruit moths and fruittree leafrollers are just starting to be caught in traps with low numbers.

My colleague, Phil Schwallier, is starting to run the carbohydrate thinning model for the season. Some growers are considering to start thinning at the beginning of bloom. Most apple blocks have an abundant crop of flower buds. According to a message from Schwallier last night, “Southeast Michigan carbohydrate thinning model predicts high stress during bloom because of the cloudy forecast. If thinning during bloom for the next two days, consider normal rates of NAA at 7 to 10 ppm or MaxCel at 75 to 100 ppm. If thinning on May 7, 8, 9 or 10, reduce rates to 5 ppm of NAA or 50 ppm of MaxCel. This is a forecast and could be not that cloudy.”

Petersburg carbohydrate model
The Cornell Carbohydrate Thinning Model for southwest Michigan as of May 4, 2015 in Petersburg, Michigan.

Pears are at open cluster to early white bud. Pear psylla eggs started to be seen late last week with high numbers of adults continuing.

Peaches are at pink for those growers with a crop. Most peach buds were killed this winter to extreme cold temperatures. I am encouraged to see there is some bloom that survived the winter cold events, mainly to the south and in the Romeo, Michigan area. The surviving buds are mostly on younger, more vigorous trees. Cover sprays for brown rot are being applied where there is a crop.

Sweet cherries are at full bloom. I am encouraged to see a fairly good bloom in sweet cherries, much better than I expected. Flowers at this time, however, do not mean fruit later in the season. Brown rot and cherry leaf spot cover sprays have been applied at most farms.

Tart cherries are approaching full bloom. Brown rot and cherry leaf spot cover sprays need to be applied soon.

European plums are at king bloom and Japanese plums are at full bloom. Some varieties of Japanese plums have severe damage from winter cold temperatures, with few flowers being seen; younger limbs have more flower buds on them. Black knot, brown rot and leaf spot cover sprays have been or will be applied soon at most farms.

Small fruits

Grapes are at bud burst for Concord types and no movement or growth for European types. There is extensive winter cold damage to wine grapes; however, damage varies greatly between varieties and sites.

Strawberry leaves are continuing to emerge from the ground; flower buds have started to emerge at most farms. Michigan State University Extension recommends strawberry growers monitor soil moisture conditions closely in both newly planted fields and established plantings as our soils are dry at most farms. Angular leaf spot lesions on leaves have been seen at one farm. Canadian thistle sprouts have been seen at many farms in the past week or so, more than I have ever seen in any season.

Raspberry canes of summer fruiting types are continuing to show leaf growth, except for the tips of canes that were killed during cold temperatures this winter. Summer fruiting canes also have a significant amount of cambium browning, indicating potential winter injury. Fall raspberry canes continue to emerge from the soil, but are not putting on much extension growth yet. The longest canes are about 4 inches long.

Blueberries are at 0.25-inch green to early pink bud. I am encouraged to see many buds that continue to swell, more than I expected. My initial bud assessments earlier this spring indicated more extensive winter cold damage in flower buds. 

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