East Michigan fruit update – May 30, 2017

Strawberry growers in the southern parts of the region will begin harvest in the next four to five days. Our season has jumped ahead again with warm temperatures last week.


Warm temperatures again last week continued to push our degree day totals ahead of normal. Our season has moved to being three to seven days ahead of normal in terms of degree day totals and growth stages. This flip flopping season has been a tough one for fruit growers. Besides the warm to cold and back to warm temperatures this spring, the windy conditions have made spraying very difficult. Both tree and small fruits put on a good amount of new growth during the last week.

I had one report of pea-sized hail in thunderstorms that moved over the region on Sunday evening.

Most of our region has received rain over the last week. Many of our MSU Enviroweather stations have recorded small amounts of rain in five of the last seven days. The rainfall totals over the last week are extremely variable, ranging from no rain to 1.4 inches.

East Michigan growing degree day totals for March 1 to May 29, 2017





Commerce (Oakland County)




Deerfield (Monroe County)




Emmett (St Clair County)




Flint (Genesee County)




Freeland (Saginaw County)




Lapeer (Lapeer County)




Pigeon (Huron County)




Romeo (Macomb County)




Tree fruits

Apples are mostly 18 to 24 millimeters in size. The chemical thinning window is now closed for most apple varieties. I have not seen any June drop as of yet. Most growers are going to need to do some hand thinning later in summer for fruit growing on good sites and close to wind machines. While the ragtag bloom has ended for bearing apples, this week I am starting to see bloom in newly planted trees. Fire blight infection is a concern on these trees if the right set of rain and warmth occurs.

Reports have continued to be received of frost and freeze damage in apples from the May 8 and 9 cold temperature events. Much of this damaged fruit has dropped. Most growers lost a good amount of apples from these frost events, with the exception of apple growers south of the I-94 corridor who have lesser amounts of damage than other growers. The range of crop loss is as high as 80 percent loss, with most growers who saw damage being in the range of a 30 to 40 percent loss. A few growers still have a full apple crop. There are also fair amounts of apples being seen with frost rings.

The new insect pests to report this week in apples are white apple leafhopper and first catch of the brown marmorated stink bug on a sticky trap. The numbers of white apple leafhopper adults are very low at the time. The brown marmorated stink bug catch is from overwintering adults, and are not considered a pest at this time of the season. It will become a possible pest when the nymphs from this adult begin feeding on peaches in July later in the season on apples. Last week I reported woolly apple aphids and European red mites as new pests, but their numbers remain low.

While not a pest new, very high trap catch is being seen for codling moth and oriental fruit moth. Very high (30 to 70) codling moth trap catch was being found last week in non-mating disrupted blocks, but this week I had several matting disrupted blocks reach biofix numbers. Good numbers of oriental fruit moths are also being caught in traps, mostly in non-mating disruption blocks. While plum curculio adults were reported two weeks ago, I have yet to see any fruit stinging. We have not had any warm nights yet this season that would foster this fruit stinging activity by plum curculio. We are not out of the woods here yet on the need to control plum curculio. Beneficials continue to be found, but their numbers are generally lower than most years.

Powdery mildew and apple scab symptoms on apple leaves continue to be seen in light numbers in a few apple blocks. Apple scab spore discharge continues with each rain event. While the apple scab model shows that all spores are mature, we still need a few more rain events for the remaining spores to be released. This might occur early this season, but in the meantime apple growers need to remain covered for apple scab. As discussed earlier in this report, with bloom being seen in newly planted trees, growers need to concerned about fire blight infections. Consult the MSU Enviroweather MaryBlyt prediction model to determine fire blight infection events. I have not seen any fire blight shoot strikes yet this season.

Pears are mostly 11 to 13 millimeters in size, although it is hard to find any pears in most blocks due to loss from frost. The little fruit that remains is scared with frost marks and rings. All stages of pear psylla continue to be found.

Peaches are mostly at 13 to 16 millimeters in size, with most growers having a good crop. Peaches are not at pit hardening yet. With the potential for such a large crop, thinning operations need to begin soon. A few green peach aphids are being seen. Oriental fruit moth trap catch continues to be found in high numbers in most non-mating disrupted blocks. Yesterday I just started to see a few leafs infected with peach leaf curl.

Sweet cherries are at 14 millimeters in size, with most of the smaller sized fruit now dropping off. We are at pit hardening. Most growers have a nice crop of sweet cherries this season. A few flower thrips continue to be seen.

Tart cherries are mostly at 10 to 11 millimeters in size. We are not yet at pit hardening. Most growers report that they have a good tart cherry crop this season.

Plums are at 14 millimeter for European types and Japanese types are at 19 to 20 millimeters in size. Some Japanese varieties have little to no crop on them this season.

Small fruits

Strawberries are maturing quickly for growers in the southern parts of the region; a few growers are considering beginning harvest late this week or this weekend. Most other growers have thimble sized to slightly larger fruit with just a few flowers remaining open in later varieties. Late last week strawberry growers started to see improved leaf growth. This poor plant growth was mainly related to cold temperatures and cooler than normal soil temperatures. I have not seen any strawberry clipper or tarnished plant bug damage in strawberries this season. I have not heard or seen any new reports of angular leaf spot in the last week.

Raspberry leaves continue to emerge on summer bearing raspberries, with flowers on early fruiting varieties now open. Fall raspberry varieties are starting to have better growth after been frosted and burning back in the May 8 and 9 freezes. The longest canes are about 14 inches in length, with most being about 8 inches.

Blueberries have just a few flower blossoms left on the plant, with the largest fruit being 8 to 9 millimeters in size. Overall, we have a very nice blueberry crop this season at most farms. I have not found any signs of mummy berry mummies on the ground as of yet this season.

Grapes are mostly between 6 and 8 inches of new growth with the longest canes at 20 inches. Flower clusters continue to elongate.  

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