Southeast Michigan fruit regional report – May 20, 2014

Many fruit insect and disease pests have made an appearance in the last week in Southeast Michigan.


Major rain events have been the story for many fruit growers in the last week. Most fruit growers report receiving 2 inches of precipitation in the last week; however, this figure varies greatly over short distances. I have heard rainfall totals of 4 to 5 inches last week from many fruit growers. With the rain events of the last week and the heat over the last few days, disease and insect pressure has mounted. Pest control operations have been in full swing at most fruit farms over the past week.

Our season continues to run behind normal by four to seven days. Scattered frost was reported at many locations on Friday, Saturday and Sunday mornings, May 16-18. At several farms, it was cold enough that strawberries needed to be frost protected, but not cold enough for damage to other fruit crop flower buds.

In last week’s regional report I reported that most fruit growers were done with planting for the season. For those growers who have not been able to finish their planting, they have been in a long and frustrating holding pattern waiting for soils to dry out enough to plant.

East Michigan growing degree day (GDD) totals for March 1 to May 19 , 2014





Commerce (Oakland)




Emmett (St Clair)




Flint (Genesee)




Lapeer (Lapeer)




Petersburg (Monroe)




Pigeon (Huron)




Romeo (Macomb)




Tree fruits

Apples were in full bloom in the southern parts of the region last Thursday or Friday, May 15-16, and in full bloom in the Flint, Michigan, area as of Sunday or Monday of this week, May 18-19. Most growers are not seeing as many flowers as they had seen as potential swelling buds a few weeks ago. Some varieties are light on bloom, including Fuji, Red Delicious and Honeycrisp at many farms, although this varies greatly from block to block. There is also a fair amount of bloom on one-year-old wood and not enough on older and more productive wood.

Many growers are concerned that we have not had good pollinating weather for apples in the last week. While there are an unusually high number of bumble bees this year, growers report seeing far fewer than normal numbers of honey bees working in the orchard.

Early last week I started to receive inquiries from apple growers concerning slow and abnormal growth on trees growing on M.9 rootstocks. Jonathan and related strains are mostly affected, but yesterday, May 19, I saw damage in many other varieties. Investigation of these symptoms points to potential winter injury to the tree trunk just above the graft union. The cambium in the trunk is dark brown with the majority of the damage on the east and north sides of the trunk. While M.9 is reported to be moderate to good in terms of hardiness, it is generally thought that it stops growth of the scion relatively early permitting increased early hardening of the scion.

With the late fall of 2013 and the extreme cold temperatures in many areas occurring the first few days of January, there is a good likelihood that trees on M.9 rootstock did not have time in the fall and early winter to completely harden off. While it’s hard to predict how many of these trees will recover from this injury, it is becoming clear that if trees were under any stress last season, they look to be severely affected and most likely will not survive. More time is needed to determine the entire impact of this problem.

Insect pest pressure has greatly picked up in the last week with many pests seen for the first time in the last few days. This list includes plum curculio, codling moth, green fruitworm, tufted apple bud moth and many leafroller species. Oriental fruit moth trap catch was very high last week as well. Tarnished plant bug numbers are also rising quickly. European red mite eggs started to hatch last week, and this week I am finding a few two-spotted spider mites in apples and other tree and small fruit crops.

Spotted tentiform leafminer adults caught in traps are the only insect pest where numbers are quickly declining. It is the end of first generation flight. With apples in bloom and in full bloom, Michigan State University Extension reminds growers that control of these pests is not an option at this time, but growers will need to keep a close eye on petal fall to get their controls on quickly.

With bloom, the risk of fire blight infection is now upon apple growers and most farms have made one or two streptomycin applications in the last week. All of our Michigan State University Enviro-weather stations recorded one or two heavy apple scab infection periods in the three to four wetting events of the last week. We continue to have apple scab spore release in each rain event; spore numbers are starting to slightly decline. The past two weeks has been frustrating for apple growers dealing with so many apple scab wetting events and spraying when soils are so wet.

Pears are mostly at late bloom to just beginning petal fall. Pear psylla adults continue to be very active when we have warm days, with all stages now being present. Pear growers need to keep an eye out for fire blight infections.

Peaches continue to look tough, with many varieties not leafing out. I have not seen one peach flower this season. In the last week or so, I have seen a few leaves emerging from the most vigorous shoots in the tops of trees. It is too early to tell if this is a sign of hope that these peach trees might survive the extreme cold winter and be viable to bear a crop of fruit in future years. I need to watch this growth carefully over the next few weeks or so to see if this growth continues or collapses when under the first stress of the season. Trees that were under stress last season or are past their prime-bearing age appear to be dead or dying.

Cambium tissue in twigs, scaffold branches and even trunks that was damaged from cold temperatures this winter is turning to a darker brown color. This is another bad sign for the potential of longer-term injury in peaches. It appears that there is extensive winter damage in peaches this season, comparable to cold damage that occurred in the winter of 1994.

Sweet cherries are at petal fall to remaining in the shuck, depending on the variety.

Tart cherries are at late full bloom to early petal fall. It appears that we have a nice tart cherry crop coming along this season.

Plums are mostly in the shuck for European types and some of the Japanese plums are just beginning shuck split. With plum curculio active, shuck split sprays will be needed soon.

Small fruits

Grapes are at late bud swell to bud burst for Concord and Niagara. Wine grapes have extensive cane death in most varieties. I am still waiting for new buds to emerge from the cordons and trunks.

Strawberry flower trusses continue to emerge from the crown. I saw a few flowers open in Monroe County last Friday, May 16, and a few on the ends of rows yesterday, May 19, near Flint, Michigan. Most strawberry growers frost-protected one time in the last week, some on Friday morning, some on Saturday morning, and even others on Sunday morning.

Strawberry clippers are being found at many farms; in fact, I am seeing more clipper damage than I have seen for the last 10 to 15 seasons. These will need to be controlled soon. I am also finding a few tarnished plant bugs, as well as two-spotted spider mites at one farm. Angular leaf spot disease has been found at several more farms in the last week, still in light amounts. Growers need to do a thorough job of scouting at this time to check for the angular water-soaked translucent lesions on leaf surfaces. A copper application may be needed at this time to control angular leaf spot.

Raspberries are continuing to show signs of winter injury, especially summer red and black raspberries and blackberries. Some growers have mowed off some summer raspberry varieties because of lack of growth due to winter injury. This winter injury is variety-specific. Canes of summer fruiting types have a significant amount of cambium browning, indicating potential winter injury. Fall raspberries continue to emerge from the ground and are now 6-8 inches in length. New canes of blackberries are finally emerging from the soil. All of the canes from last season are dead to the ground.

Blueberries are mostly at late pink bud to early bloom. The flowers and leaves have turned deep red due to cold temperatures. They will green up again with warmer temperatures. Twigs continue to die in many blueberry varieties due to winter injury.

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