2020 Apple Maturity Assessments: Week 2 Honeycrisp and Crimson Gala

• Honeycrisp fruits evaluated in Maryland have not received any plant growth regulator application and are ready to be harvested. Thus, this was our last maturity assessment on Honeycrisps grafted in different rootstocks at Keedysville.
• Fruit from PA received an application of ReTain (1/2 pck/ac) on 8/27 and still need more time until harvest.
• All the information is summarized in Table 1.

Honeycrisp Results

This week we can observe differences among fruits grafted on different rootstocks at Keedysville, MD. Fruits grafted on G30 show the most advanced maturity, are tree-ripe and ready to be harvested for fresh market, whereas fruits grafted on V1 and G11 are ready for harvest for storage, and fruits grafted on G969 should as well be ready to be harvested for storage this week, despite showing a slightly delayed maturity trend.

Between locations, MD fruit presents a more advanced maturity as compared to fruit from Aspers, PA. These differences are enhanced due to the application of ReTain (1/2 pck/ac) in Honeycrisp fruit from PA. For more detailed results on specific quality parameters please read below:

Color

Surface color

Honeycrisp fruits harvested from Maryland show 35-65% of red skin coloration, with fruits grafted on G30 and G969 showing the highest and lowest values, respectively. Fruits harvested from PA present a lower red skin coloration but had an important increase since last week (10% to 30%).

Background color (DA index)

Values for all fruits harvested from most rootstocks in Maryland displayed values of 0.9-1.0, significantly lower than last week (1.3-1.4), while fruits grafted on G30 present the lowest values (0.6). Lower values are indicative of more advanced maturity, as was the case for fruits grafted on G30, which are tree-ripe and ready to be harvested for fresh market.

Fruit firmness

Honeycrisp fruit assessed in MD are displaying firmness values between 13.8-14.5lbs, indicative of fruits that are ready to be harvested for short-term storage or fresh market. Honeycrisp fruit from PA maintains the average of ~2lb higher firmness (16-17lbs) values as compared to Maryland but also presented a decrease in firmness as compared to last week. Fruit for long-term storage (> 3 months) should be harvested with firmness of at least 15 lbs.

Starch content

The common starch index rating system (Cornell chart) on a scale from 1 to 8, where 1 is full starch (all blue-black) and 8 is starch-free (no stain), was used to evaluate the fruits. Honeycrisp fruit from PA is still at the lower end of the scale (1.3). MD fruits displayed significant differences within assessed rootstocks, ranging between 4.4 to 7, another indicator that they are ready to be harvested. Fruits with values ranging from 4-6 (G11, G969, and V1) are recommended for long-term storage, while 6-7 (as displayed by fruits grafted on G30) for fresh market.

Soluble solids contents (SSC)

SSC values increased for all fruits evaluated this week, with values > 12% in all cases. In general, it is recommended to harvest fruits with readings around 12% to 14% SSC.

Acidity

Malic acid values tended to decrease in all assessed fruits irrespective of rootstock and location, as expected, due to fruit ripening. MD fruit are showing lower acidity values as compared to PA fruit, maintaining the trend observed last week.

Comparison between Honeycrisp and Crimson Gala Results from PA fruit

Honeycrisp and Crimson Gala were evaluated on the same day in Aspers, PA after both had received a ReTain application. Like last week, Galas are displaying a more advanced maturity stage compared to Honeycrisp, with the exception of firmness and soluble solids. In general, Galas are showing a higher red skin coloration (60% vs 30%), lower DA index (readings of 0.9 vs 1.2), higher starch index (scale rating of 2.7 vs 1.2), and lower acidity (0.4% malic acid vs. 0.6%), with respect to Honeycrisps; but are also displaying a lower rate of softening/higher firmness (~21lbs vs. ~16lbs for Honeycrisp) and lower soluble solids (11.9% vs 12.9%) than Honeycrisp.

We will continue evaluating Honeycrisp and Crimson Gala from PA, whose harvest at our sample location is anticipated to happen close to each other. It is important to continue monitoring fruits by using different maturity indices as an individual index does not adequately reflect fruit maturity. Furthermore, we recommend continuing to closely monitor both cultivars due to variations among locations, orchard blocks, plant growth regulator applications, and rootstock.

Table 1. Summary table of maturity assessments for Honeycrisp and Crimson Gala. Values in parentheses indicate the results from last week's monitoring. For PA fruit labeled with *, a ReTain application at ½ rate (½ pk/ac) was done on 8/27.

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