Northwest Michigan apple maturity report – Sept. 12, 2018

Maturity is moving along quickly and starch index readings have jumped in the past week. Color has also improved with the cooler temperatures.

San Jose scale on Honeycrisp
San Jose scale on Honeycrisp fruit. Photo submitted by a local consultant.

General apple harvest comments

As we moved from August into September, the conditions almost seemed to flip a switch from summer to fall. Days are filled with nice sunshine, and as soon as the sun sets, temperatures drop for the overnight. Recent daytime temperatures are in the high 60s to mid-70s, and nighttime temperatures dip into the mid-50s. These are relatively normal conditions for fall in northwest Michigan.

Forecasts are predicting warmer temperatures for the remainder of the week, and we will likely see daytime temperatures reach into the 80s. Nighttime temperatures will still be cooler but predicted to be in the mid- to low 60s rather than in the 50s. There is little rain in the forecast, and the next potential rainfall event is predicted on Sept. 18; however, the chance of rain is still below 50 percent.

From discussions in the region, most growers are pleased with how the apple crop is shaping up this season. Color is a concern, but we are still relatively early in the season, and the recent sunny and cooler conditions will improve color. Most varieties are eating much better this week. Starch removal ranges are relatively low, but these numbers increased over the past week. Starch removal numbers for most varieties are in the range of 1-3, but the fruit is tasting really good for this point in the season. In some blocks, fruit size is on the smaller side, likely as a result of the early dry conditions. However, size is better than growers were predicting earlier in the season. There is a lot of Retain going on apples this season.

This is the third 2018 apple maturity report for northwest Michigan, and these data show the following apple varieties are ripening. Gingergold harvest is wrapping up, and SweeTango harvest is ongoing—growers have seen a small amount of cracking in this variety with the high levels of rainfall in certain regions last week. We have received reports of some blocks where San Jose scale damage on Honeycrisp fruit has been observed (see photo). With our sandy soils, orchards dried out quickly after the rains last week, so the wet weather did not impact harvest timing much.

Apple maturity in northwest Michigan for apple collected on Sept. 11

Variety

Firmness lbs. (range)

Starch (range)

Brix

Color %

McIntosh

16.8 (16.6-16.9)

1.9 (1.9-1.95)

11.8

79.3

Gala

20.2 (20.1-20.3)

1 (1.0-1.0)

10.95

78

Honeycrisp

16.6 (15.7-17.3)

3.2 (2.2-3.9)

12.1

72.1

Individual apple variety results

McIntosh firmness is steadily decreasing, while starch indices and brix remain similar to last week. Color is improving, but warmer weather will be a challenge to continue this trend. McIntosh size is promising.

McIntosh maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Aug. 27

19.4

1

10.4

71.5

Sept. 4

17.7 (17.6-17.8)

1.2 (1.1-1.3)

11.3

73.8

Sept. 11

16.8 (16.6-16.9)

1.9 (1.9-1.95)

11.8

79.3

Gala color is improving substantially compared with last week; size is also improving. These apples are still very firm, and overall has been little change in firmness, starch indices and brix over the last three weeks. Warmer weather will help to mature this variety.

Gala maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Aug. 27

22.65 (22.6-22.7)

1.0

9.85

39.2

Sept. 4

21.6 (21.3-21.9)

1.03 (1.0-1.05)

10.15

54

Sept. 11

20.2 (20.1-20.3)

1 (1.0-1.0)

10.95

78

Honeycrisp maturity is moving quickly. The most noticeable changes are in color and starch indices. Firmness is decreasing, while brix is increasing. We caution growers that this variety could move very quickly in predicted warm temperatures. We are continuing to observe internal browning in Honeycrisp samples from the Northwest Michigan Horticulture Research Center, but this browning has not been observed from on-farm samples. A relatively low incidence of bitterpit is apparent in several blocks, but overall growers are pleased with the low levels of bitterpit in most orchards.

In more southerly orchards where rainfall was higher than in the northwest, Honeycrisp fruit has a higher than normal water content. We have observed juicy Honeycrisp in northwest Michigan, but the water content does not seem abnormally high.

Honeycrisp maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Aug. 27

19.8 (19.1-20.3)

1.1 (1.0-1.3)

10.7

45

Sept. 4

17.2 (16.7-17.7)

1.5 (1.2-1.6)

11.6

56.9

Sept. 11

16.6 (15.7-17.3)

3.2 (2.2-3.9)

12.1

72.1

 

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.


Michigan State University Michigan State University Close Menu button Menu and Search button Open Close