West central Michigan tree fruit update – June 19, 2018

Updates on tree fruit development stages, diseases and pests in west central Michigan.

Tree fruit development has continued to move forward at a rapid pace after a slow start to spring. Growing degree-day (GDD) accumulations are now ahead of this time last year, and the timing of development and GDD accumulations are most closely resembling 2016 at this time. Many growers are using this comparison to estimate harvest dates for sweet and tart cherries.

West central Michigan GDD accumulations


GDD base 42 current

GDD base 45 current

GDD base 50 current

Benona / Shelby




Elbridge / Hart












Tart cherries are full yellow or early in red color development across the region. Growers in earlier locations are expecting to start shaking near the end of the first week or beginning of the second week of July. The crop currently looks to be of good quality and fairly heavy.

Cherry leaf spot has shown up in many locations in the past several days, although damage so far does not appear to be extensive. Powdery mildew has been generally low, and American brown rot has not been reported on tart cherries at this time.

Spotted wing Drosophila (SWD) have not been caught as of July 14, 2017, in west central Michigan, but first catches in the northern and southern parts of the state last week prompted many growers with yellow or pink fruit to put the first SWD cover out with the fungicide cover that went out in the early to middle part of this week. Plum curculio activity has been in decline for several days and activity is likely over for the season.

Apples are between 20 and 30 millimeters, depending on variety. The crop generally looks good, although there are areas with a spotty crop. Poor pollination and excessive thinning during the major heat wave in late May are thought to be the cause of sites with poor set.

Apple scab has been declared over in west central Michigan as of June 19, and incidence of this disease is generally very low this year. Fire blight began to show up early last week in many areas and has continued to be reported through the early part of this week. Challenging fire blight conditions near the end of bloom may have caused growers some issues, but fortunately most locations just have isolated strikes as opposed to epidemic levels. No reports of loss of young trees have come in at this time.

Codling moth biofix was set at May 26 and we are in the middle of the hatch of eggs laid by the first generation. Growers are actively managing blocks that have gone above a cumulative trap catch of five moths.

Sweet cherries are sizing and coloring rapidly, with most growers expecting to start picking early fresh varieties by the last two to three days of June. Quality of the crop looks generally good and is heavy.

Bacterial canker has been minimal this year, growers generally attribute this to better pruning practices and a span of dry weather that allowed pruning cuts to dry out and heal this past spring. Brown rot is starting to show up, particularly in older sweet cherry trees with high, dense canopies. Sweet cherry growers started their SWD management programs with their cover fungicides this week. Plum curculio are declining at this time, and are likely done damaging sweet cherries for the season.

Peaches are 25-30 millimeters in diameter at this time, pit hardening is still at least a couple of weeks away for most sites. The peach crop is very heavy in most locations and will have to be hand-thinned well to attain desired size and minimize split pits.

Little to no bacterial spot has been reported this year, and brown rot has not started to show up on fruits yet. First generation of oriental fruit moth is over, and shoot strikes caused by feeding larvae will likely show up in the next several days. No second generation flight has been detected at this time. San Jose Scale adults from last year have been observed in heavy numbers in several older peach blocks in the region, prompting many growers to plan on targeting crawlers with an application in the third or fourth week of June.

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