Northwest Michigan apple maturity report – Aug. 29, 2018

Apple harvest has begun and consecutive days of stormy weather seem to have had little negative impact on the northwest apple crop.

General apple harvest comments

Early reports suggest the apple crop is still looking pretty good following a few consecutive days of stormy weather. Some blocks, particularly those without irrigation or those with heavy a crop load, were challenged with relatively smaller fruit size due to droughty conditions earlier this season. However, recent rainfall has been helpful for sizing fruit.

Several varieties are showing some color, but the trend of mostly warm temperatures has not been conducive for coloring fruit. Cooler evenings in the forecast should help fruit color up. With fruit starting to ripen, crop load variability in blocks is becoming more noticeable. Some orchards had a substantial number of fruit that dropped “naturally” (i.e., due to weather rather than chemical thinners) this season.

At the Northwest Michigan Horticulture and Research Center, we tested precision crop management and our Honeycrisp crop load is promising. Thus far, we have not received reports of extensive damage to fruit as a result of stormy weather, but several growers have been cleaning up debris and repairing deer fences and trellises impacted by windy conditions/fallen trees. Growers of early apple varieties (ex. Zestar, Gingergold) are harvesting in the region.

Several stink bug species seem to be in high abundance this season and we have observed some feeding damage that resembles stink bug feeding on fruit this season. This summer also seemed to favor plum curculio activity, and in blocks impacted by this pest, old oviposition scars have expanded on the growing fruit. Apple maggot activity was low in our region, likely as a result of drier conditions.

Mites have been particularly challenging in this summer’s hot and dry conditions and many orchards had noticeable bronzing. Fortunately, mites seem to be slowing down at this time as European red mites are entering their overwintering phase, and the wet, cooler weather is not favorable for spider mites.

San Jose scale crawlers have been settling in new feeding sights, and red rings that form around the settled immature scale on fruit can be found in our infested block at the station. San Jose scale male trap numbers have been very high this season, and like mites, scale also thrived in the hot and dry weather.

This season was the first season we found brown marmorated stink bugs in traps in northwest Michigan orchards. While trap numbers of brown marmorated stink bugs in orchards have been low, populations in urban areas of our region have been growing; adult brown marmorated stink bugs and nymphs are active at this time.

This is the first 2018 apple maturity report for northwest Michigan and these data show that at the time of sampling, these apple varieties were firm with low starch indices and not quite ready for picking.

Apple maturity in northwest Michigan for apple collected Aug. 23 and 27

Variety

Firmness lbs. (range)

Starch (range)

Brix

Color %

Gingergold (Aug.23)

20.5

1.1

11.5

N/A

McIntosh (Aug. 27)

19.4

1

10.4

71.5

Gala (Aug. 27)

22.65 (22.6-22.7)

1

9.85

39.2

Honeycrisp (Aug. 27)

19.8 (19.1-20.3)

1.1 (1-1.3)

10.7

45

 

Suggested firmness and starch index levels for long-term and shorter-term controlled atmosphere (CA) storage by variety.

Variety

Firmness (pounds)*

Starch Index*

Short CA

Mid-CA

Long CA

Mature

Over mature

McIntosh

14

15

16

5

7

Gala

16

17

18

3

6

Honeycrisp

15

16

17

3.5

7

Empire

14

15

16

3.5

6

Early Fuji

16

17

18

3

7

Jonagold

15

16

17

3.5

5.5

Jonathan

14

15

16

3.5

5.5

Golden Delicious

15

16

17

3

6.5

Red Delicious

16

17

18

2.5

6

Idared

14

15

16

3.5

6

Fuji

16

17

18

3

7

Rome

15

16

18

3

5.5

*Firmness is measured with a mechanical 11-millimeter wide probe inserted into the pared flesh of a fruit to a distance of 8 millimeters. Starch index is measured on equatorial cross section of an apple stained with iodine solution and rated using the Cornell University starch-iodine index chart for apples on a 1-8 scale (Predicting Harvest Date Window for Apples by Blanpied and Silsbey, Cornell Extension Bulletin 221.)

Looking for more? View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.


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