Photo: Kathy Hunt, University of Maryland
The onset of cooler weather followed by killing frosts in the third week of October greatly improved red color development in the late-season apples. Unfortunately, that cool weather also triggered preharvest drop in some varieties. We also noted that October-harvested fruits have lower soluble solids than in the past few years. Consequently, GoldRush, Granny Smith and Cripps Pink still taste acidic despite softening and losing much of their starch.
This month we added four October varieties to our evaluations: BC-2 Fuji, GoldRush, Granny Smith and Cripps Pink (Pink Lady). Maturity data for these four varieties are shown in Table 1.
October Apples – Central Maryland
(Keedysville, Washington County)
|Cultivar||Date||Diameter (inches)||Red Color (%)||Ground Color||Firmness (pounds)||Starch Pattern (1 – 8)||Soluble Solids (°Brix)|
|Fuji (BC-2)||October 7, 2018||3.1||28.0||Greenish yellow||14.5||6.4||15.3|
|October 19, 2018||3.2||42.0||Greenish yellow||14.4||7.7||14.4|
|October 30, 2018||3.3||55.0||Light yellow||15.0||7.7||16.0|
|GoldRush||October 7, 2018||3.2||0.0||Yellowish green||21.9||2.7||15.1|
|October 19, 2018||3.3||12.0||Greenish yellow||21.3||4.8||17.6|
|October 30, 2018||3.1||20.0||Light yellow||21.0||4.9||18.0|
|Granny Smith||October 7, 2018||3.1||0.0||Whitish green||19.8||3.8||12.0|
|October 19, 2018||3.2||12.0||Whitish green||17.6||4.9||14.0|
|October 30, 2018||3.3||17.5||Light green||16.8||5.5||14.0|
|Cripps Pink||October 7, 2018||2.9||18.0||Greenish yellow||21.5||1.7||12.3|
|October 19, 2018||3.1||45.0||Greenish yellow||19.5||4.9||13.6|
|October 30, 2018||3.0||62.6||Greenish yellow||19.7||6.2||14.8|
Table 1. Changes in maturity and quality of late-season apple cultivars spot-picked in Central Maryland during October 2018.
By mid-October Fuji fruit at Keedysville had softened considerably and had excellent eating quality. They were developing varietal flavor with good texture and little starch left in the fruit. This week’s Fuji samples continued to hang on the trees despite being devoid of starch. While mid-October harvested Fuji did not have water core, all fruit sampled this week did have water core.
GoldRush were the largest fruit we evaluated, with high soluble solids (18.0 Brix). Despite that very high level of sugar, GoldRush apples still tasted acidic. When we measured the starch pattern index of these greenish-yellow fruit, we again noticed great variability. The mean starch pattern index was 4.9 with individual fruit ranging from 3 to 6, using the Cornell Starch Chart.
The high level of sugar in the flesh and rough peel makes GoldRush quite susceptible to cracking. While we did not see any severe fruit cracking in our trials in Central Maryland, some cracking has been seen at other locations. In addition to noting fruit-to-fruit variability in GoldRush, we also noted that visible attributes (size and color) did not always predict the hidden qualities of firmness and starch (Photo 2).
Granny Smith and Cripps Pink
With the first frost, red color began to develop in these two late-October varieties. Granny Smith was initially maturing ahead of Cripps Pink and ready for long-term storage in the third week of October. By the end of October, both varieties appeared ready for long-term storage (Photo 3). The cooler weather in October should make the fruit less likely to develop superficial scald in storage. Since sugar development has been slow this year, and fruit are still acidic, it might be tempting to wait to pick. Based on the firmness and starch readings, Cripps Pink should certainly be picked by Election Day. Last year some growers waited too long to pick Cripps and wound up losing considerable fruit in a mid-November freeze.
These observations were made by spot-picking fruit grown on supported trees budded onto size-controlling rootstocks. Small differences in microclimate or orchard management practices can make a large difference in maturation. Management practices that might hasten fruit maturity are summer PGR applications to enhance return bloom, mechanical pruning to increase red color development, choice of rootstock and the use of stop-drop sprays.
Photo 1. Red color development in Cripps Pink apples in a vigorous tall-spindle planting at the Western Maryland Research and Education Center in Keedysville on October 30, 2018. Photo: Kathy Hunt, University of Maryland
Photo 2. Ground color of GoldRush apples does not always predict hidden qualities such as fruit firmness, acidity, and starch-staining pattern. Notice that the yellowest apple (lower left) has the greatest amount of starch in the flesh. Photo: Kathy Hunt, University of Maryland
Photo 3. Red color development and starch-staining pattern of Cripps Pink (upper) and Granny Smith (lower) apples picked on October 30, 2018. Photo: Kathy Hunt, University of Maryland