Category Archives: Harvest maturity

Apple Maturity Report for September 16

We checked the maturity of apples growing at the Alson H. Smith, Jr. AREC on September 16.

With clear days, dry conditions, and cool nights we couldn’t ask for a better stretch of weather. Many growers are starting to pick their main cultivars, including Red Delicious and Golden Delicious. Data from the AREC show that both of these cultivars are still in an ideal window for long-term storage. Jonagolds and Empires are entering into the ideal harvest window. Idareds and Romes are probably a week or so away, and Yorks are probably two weeks away from their ideal harvest maturity.

Below are all of our harvest data for 2014.  Click on this sentence to learn more about the different maturity indices.

Maturity Report 2014, Virginia Tech        
Sample Collection Date Cultivar Location Number of Orchards Tested (10 Fruit Each) Background Color (1-4)* Red Color (%) Firmness (lbs) Soluble Solids (ºBrix) Starch-iodine Index       (1-8)** Fruit Diameter (inches) Fruit wt. (g) Ethylene (ppm)
8/18/14 Gala (Crimson) AHS JR AREC 1 80.4 23.2 11.2 1.1 2.66 144 0.0
8/25/14 Gala (Crimson) AHS JR AREC 1 93.2 20.0 13.3 3.4 2.79 162 0.4
8/25/14 Gala (Buckeye) AHS JR AREC 1 98.7 21.6 14.9 4.0 2.79 172 1.6
8/18/14 Golden Supreme AHS JR AREC 1 3.1 18.1 10.9 1.7 2.88 174 0.0
8/25/14 Golden Supreme AHS JR AREC 1 2.6 16.9 11.5 2.6 2.82 166 0.0
8/25/14 Golden Delicious Winchester 12 2.2 18.6 12.4 1.5 2.85 166 0.0
9/16/14 Golden Delicious Winchester 2 2.9 16.3 13.5 4.6 2.82 161 0.0
8/18/14 Honeycrisp AHS JR AREC 1 53 18.5 11.8 1.1 3.27 232 0.0
8/25/14 Honeycrisp AHS JR AREC 1 55 15.8 13.0 1.8 3.36 247 4.9
8/25/14 Red Delicious (Scarlet Spur) Winchester 1 91 19.2 10.9 1.3 2.90 179 0.0
8/25/14 Red Delicious (Red Chief) Winchester 2 80 19.3 10.6 1.2 2.92 182 0.0
8/25/14 Red Delicious (Nured) AHS JR AREC 1 87 18.0 9.8 1.1 2.83 166 0.0
8/25/14 Red Delicious (Redspur) Winchester 1 64 18.6 11.2 2.1 2.93 182 0.0
8/25/14 Red Delicious (Ace) AHS JR AREC 1 95 19.7 10.8 1.0 2.78 160 0.0
8/25/14 Red Delicious (Bisbee) AHS JR AREC 2 86 18.9 10.9 1.3 2.80 163 0.0
9/16/14 Red Delicious (Nured) AHS JR AREC 1 97 17.0 11.7 2.4 2.83 167 0.9
9/16/14 Red Delicious (Ace) AHS JR AREC 1 99 19.2 13.0 2.0 2.93 187 3.6
8/25/14 Empire AHS JR AREC 3 64 18.8 11.7 1.6 2.82 148 0.0
9/16/14 Empire AHS JR AREC 1 88 18.3 12.6 2.7 2.65 126 0.6
9/16/14 Rome (Law) AHS JR AREC 1 92 21.7 12.2 3.0 2.92 163 0.3
9/16/14 Rome (Taylor) AHS JR AREC 1 50 21.6 12.4 3.0 3.14 203 0.0
9/16/14 York AHS JR AREC 2 80 23.8 11.1 1.3 2.90 161 0.0
9/16/14 Jonagold AHS JR AREC 1 81 16.3 14.2 5.4 3.30 251 0.1
9/16/14 Idared AHS JR AREC 1  – 61 15.2 12.9 2.0 3.00 180 0.0
* 1 = green, 2 = light green, 3 = yellowish green, 4 = yellow.
** 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.

 

Predicted 2014 Apple Harvest Dates

Predicting harvest date depends upon many factors, including full bloom date, accumulated heat units (growing degree days) over the course of the growing season, physiological stressors (e.g., disease and insect damage or drought), day to night temperature differentials as harvest approaches, and the amount of precipitation. However, the number of days between full bloom and harvest has been shown to be the most reliable predictor of harvest date.

Click here to learn more about pre-harvest drop management.

More than two decades ago, researchers in Michigan determined that there there are an average of 143 days between full bloom and the first commercial pick of Red Delicious apples that are to be held in controlled atmosphere storage (i.e., firmness between 17-18 lbs; starch between 2.5-4 on the 8-pt scale Cornell Starch Chart). Additional seasonal adjustments above or below the average number of days until harvest are made based upon the average daily minimum temperatures for the 15 days after full bloom.

For the past several seasons I have tested the Michigan model using fruit from a block of Bisbee Red Delicious on MARK rootstock. Results to date have shown that this model is very good at predicting harvest maturity in Virginia.

Based on the Michigan model, here are the predictions for 2014:

In Winchester, Bisbee Red Delicious full bloom was April 27 and average minimum temperature for the 15 days after full bloom was 0.5°F more than 50°F. Using this data in the Michigan model, harvest is predicted to be 143 days after full bloom. This puts the predicted harvest date for the first CA pick of Red Delicious at September 16.

In Central Virginia (Tyro), full bloom for Red Delicious was estimated to be April 20 and the predicted harvest is September 9.

If you want to compare the model to your own situation, here are the previous years’ predicted harvest dates:

2011 Winchester: September 10
2012 Winchester: August 26
2012 Central VA (Batesville): August 25
2013 Winchester: September 18
2013 Central VA (Piney River): September 15

Since most growers have Red Delicious trees in their orchards, other cultivars (and strains of Red Delicious that ripen earlier than Bisbee) can be estimated based upon experience on their picking date relative to Red Delicious.

Another method for estimating harvest date uses the rule-of-thumb that says, “for each 2-3 days departure for the normal bloom date, there will be a one-day departure from the normal harvest date.” (Blanpied and Silsby, 1992).

You can find more information about harvest maturity indices in this post.

Starting in August, I will start conducting maturity evaluations of fruit from the Winchester AREC and surrounding orchards.

References

Blanpied, G. and K. Silsby. 1992. Predicting Harvest Date Window for Apples. Cornell Information Bulletin 221. <<pdf>>

Beaudry, R., P. Schwallier, and M. Lennington. 1993. Apple Maturity Prediction: An Extension Tool to Aid Fruit Storage Decisions. HortTechnology 3(2): 233-239.

Harvest Maturity Report for October 8

On Tuesday (October 8), we sampled York, Cripps Pink (Pink Lady), Winesap, Granny Smith, Stayman, Fuji (BC2), and Suncrisp (which had ReTain and NAA applications) apples from trees on or near the AREC for this week’s maturity report. Despite the summer-like weather late last week and over the weekend, apples are continuing to ripen slowly. Fuji, Suncrisp, and Granny Smith are all showing starch degradation, (though ethylene levels remain low) and should be picked soon. We starting picking our Fuji (BC2) trees today.

York harvest started for some growers last week, and I suspect many growers in the Northern Shenandoah Valley are focusing their attention to this variety right now. The Yorks that we tested (Ramey’s and Imperial) were very firm (19.9 lbs), have excellent color (84% blush), a fair amount of sugar (12.1 Brix), and only showed a minimal amount of starch degradation (~1.3).

Pink Lady apples are already showing high sugar levels (13.1 Brix), but they are still quite starchy and varietal flavor hasn’t started to develop. I’d say they are still a couple-few weeks away from harvest.

The remnants of hurricane/tropical storm Karen is predicted to hit the region tonight, and for the first time this harvest season we are forecasted to have a prolonged stretch of rainy weather. Although the rains might slow down harvest activities, it will help to size up the later cultivars.

Click the on the link at the end of this sentence to download a copy of the 2013 Oct 8 Maturity Report.

Harvest Maturity Report for September 23

On Monday, September 23, we collected Rome, York, Fuji, and Stayman apple samples for this week’s maturity report (2013 Sept 23 Maturity Report). The weather in the northern Shenandoah Valley will remain cool, with clear sunny days for the next week. These conditions are continuing to promote excellent fruit color and varietal flavors, while also extending the harvest window for many cultivars.

Of the fruit we measured this week, Rome harvest should be starting soon (starch = 3.3; ethylene <1.0), while the main Fuji harvest crop will probably not be ready to pick until next week at the earliest. Staymans and Yorks still have very high firmness (>18.8 and 23.6 lbs, respectively) and very low ethylene (<1.0) and starch degradation (=1), indicating that it will be several more weeks until they will be physiologically mature enough for harvest.

Golden Delicious harvest is concluding for many growers, though fruit that is still on the trees has maintained a high level of quality. For a pre-harvest drop test, we did a large Red Delicious sampling late last week, and we will do another one next week. Red Delicious harvest is still ongoing, with many strains still viable for long-term storage and SmartFresh applications.

As always, due to location, rootstock, strain, and environmental factors, fruit in your orchards may be at a different maturity than the fruit at the AREC. For this reason, you should be checking blocks several times a week to ensure that you harvest at your desired maturity. More information about harvest maturity indices can be found at my post from last year.

Harvest Maturity Report for September 16

On Monday, September 16, we harvested Red Delicious, Golden Delicious, Empire, Idared, Rome, and Fuji BC2 (a late ripening strain) for this week’s Maturity Report. Based on the apples that we harvested at the AREC, Goldens are moving past the point where they should be harvested for long term storage. Reds are still OK for long term storage, but a few of the Red Delicious apples that we tested had very advanced maturity. Empires are eating well and should be picked soon. Earlier ripening blocks of Romes and Idared should be checked as they are starting to ripen at the AREC. We’re looking to start our Fuji harvest late next week.

Besides for a chance of showers over the weekend, the forecast for the next week continues  to look excellent for harvest.

Harvest Maturity Report for September 10

We harvested apples on September 10 for this week’s harvest maturity. Due to our annual Field Day and running samples for a pre-harvest drop trial, we only ran Golden Delicious, Red Delicious, and two strains of Fuji. From these data and my observations from around Frederick County, it appears that sugar content (soluble solids) are starting to come up in Golden Delicious, while starch degradation is still optimal for long term storage. Red Delicious are starting to ripen, and some early coloring strains are already being picked. I expect Red Delicious harvest to be in full swing by early next week. Early strains of Fuji are ready for harvest, but later strains still have several weeks before they will be ready for harvest. On Thursday, we’ll be harvesting Daybreak Fuji from a tall spindle planting and Rising Sun Fuji from a rootstock trial.

I expect the heat over these past couple-few days will advance apple ripening faster than what we have seen up until this time, so keep checking blocks that are near to your ideal harvest maturity. The heat is forecasted to break on Friday after which we’ll return to more moderate temperatures for at least seven days.

Click the link to the right for this week’s harvest maturity evaluation data.

Harvest Maturity Report for September 3

We collected fruit on Tuesday for this week’s maturity testing. Most growers in the Winchester area are finished or near to finishing Honeycrisp and Galas and moving into the main cultivars. Golden Delicious harvest has started, but the fruit has not advanced in maturity very much over the past week and is still very variable based on location and planting system. Compared to last week, the Goldens have lost firmness, but not starch and they have not increased in soluble solids or ethylene. Most Red Delicious strains are still at least a week away from early harvests for long term storage. This is despite the deep red colors that are developing. Picking of early strains of Fuji is underway, and like the other red skinned cultivars appear to have very nice color and size this year. Empires are starting to ripen and can probably be picked sometime in the next week, particularly if the fruit is going to be stored for any significant amount of time.

Over the next week, we are going to remain in a relatively dry weather pattern with warm but not hot days in the 80s and cool nights in the 50s and 60s. These conditions are ideal for developing color on red skinned cultivars and allowing the fruit to hang on the tree until ideal maturity and flavor has developed. We can only hope that these conditions will continue for several more weeks.

Click on the below link to download a pdf of the complete harvest maturity report for September 3, 2013.

2013 Sept 3 Maturity Report

Annual End-of-August Maturity Testing

This it the 28th year that researchers at the Alson H. Smith, Jr. AREC have recorded Golden Delicious and Red Delicious apple maturity data from orchards based in and around Winchester. Including 2013, data for Empire has been taken for twelve years and Gala for six years. In recent years, we have also added other commercially important cultivars to the analyses in order to generate long term averages. These data provide an interesting insight into the current season’s harvest, and can help growers make decisions on when to pick different blocks.

As discussed in a previous post, bloom date was about three weeks later than in 2012 and fairly close to the long-term averages. This should mean that harvest dates will be relatively “normal” or at least more similar to harvest dates in the late 1990’s through early 2000’s than they have been in the last several years.

As of this week, most growers in the Northern Shenandoah region are finishing up picking Ginger Golds, and have started picking Gala and Honeycrisp. Some growers in Central Virginia are finishing Gala and starting with Golden Delicious.

Many of the Golden Delicious blocks that we tested this week had very nice fruit finish, with minimal russet. Golden Delicious maturity was quite variable in the blocks that we tested, and it appears that some blocks will be ready to harvest within the next week, while others are probably 7-10 days away from being ready to harvest. The use of ReTain by some growers may explain some of this variability.

With the cool nights that we have experienced in August, red skinned cultivars have developed better than average color. However, be sure to check the starch and sugar levels before picking to be sure that the apples are mature enough to pick. Many Red Delicious apples that we tested this week had great color but very little starch degradation and soluble solids were only at 9-10 Brix.

Below are the data from this year’s end-of-August apple maturity sampling. In each year, the samples were taken around August 25 (August 26 this year) and consist of apples from the AREC and a few local growers. Thanks to Dave Carbaugh and Abby Kowalski for collecting and testing the fruit. Please refer to my post from last year if you need help interpreting the different maturity indices. You can also download a pdf of the 2013 Annual August Maturity Report.

Golden Delicious Maturity Report 1986-2013

 

 
Year

Background Color (1-4)*

Firmness (lbs)

Soluble Solids (ºBrix)

Starch-iodine Index (1-8)**

Ethylene (ppm)

Bloom Date

1986

2.2

19.5

12.7

1987

20.0

12.2

1988

18.6

11.0

1.5

1989

17.7

10.3

2.0

1990

18.0

10.5

1.6

1991

1.8

19.7

12.0

2.1

1992

1.8

20.1

12.0

1.6

1993

1.9

19.8

11.6

1.5

1994

2.3

19.8

12.0

1.7

1995

0.9

18.8

10.9

2.1

1996

2.9

19.6

11.2

2.9

1997

2.0

21.8

11.7

2.0

1998

2.5

19.2

12.2

2.1

1999

1.9

20.3

11.7

1.4

2000

1.8

17.5

11.9

2.5

2001

1.9

20.1

11.0

1.4

2002

2.2

21.2

11.4

2.1

2003

2.6

20.3

11.1

1.2

2004

2.3

18.2

12.3

2.0

2005

1.8

20.1

11.4

1.7

2006

1.9

18.5

12.4

1.8

2007

1.6

18.0

12.3

1.6

2008

2.1

18.3

12.9

1.6

22-23 Apr

2009

1.8

17.2

12.4

1.7

22-Apr

2010

1.6

18.6

12.9

1.4

13-Apr

2011

2.1

20.1

12.9

1.2

20-Apr

2012

2.5

18.5

13.0

1.3

0.00

2-Apr

2013

2.2

18.3

11.9

2.2

0.17

25-Apr

Mean

2.0

19.2

11.9

1.8

17-Apr

Max

2.9

21.8

13.0

2.9

25-Apr

Min

0.9

17.2

10.3

1.2

2-Apr

* 1 = green, 2 = light green, 3 = yellowish green, 4 = yellow.
** 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.

Red Delicious Maturity Report 1986-2013

Year

Red Color (%)

Firmness (lbs)

Soluble Solids (ºBrix)

Starch-iodine Index (1-8)*

Ethylene (ppm)

Bloom Date

1986

72.0

18.8

11.2

1987

68.0

19.8

10.8

1988

54.0

18.4

10.0

1.6

1989

69.0

18.6

8.7

1.6

1990

73.0

18.1

8.9

1.5

1991

69.0

18.8

10.4

1.6

1992

76.0

20.8

10.2

1.3

1993

68.0

21.7

9.5

1.7

1994

68.0

19.7

9.5

1.9

1995

68.0

19.2

9.1

1.6

1996

62.5

19.3

8.9

2.0

25-Apr

1997

66.7

22.4

9.4

1.2

25-Apr

1998

81.9

19.3

9.9

2.5

15-Apr

1999

65.5

19.8

10.5

1.9

28-Apr

2000

87.4

16.2

9.6

2.3

11-Apr

2001

61.0

20.5

8.3

1.8

28-Apr

2002

60.2

21.4

9.4

2.1

22-Apr

2003

58.4

20.4

8.5

1.9

22-Apr

2004

88.2

16.7

10.0

2.3

20-Apr

2005

73.7

18.7

9.2

2.0

24-Apr

2006

63.8

18.7

10.7

2.0

16-Apr

2007

81.1

18.1

11.0

1.7

22-Apr

2008

86.6

18.1

9.4

2.0

22-Apr

2009

79.2

17.5

10.2

1.9

24-Apr

2010

65.9

18.2

11.5

1.7

8-Apr

2011

67.5

19.8

11.5

2.1

21-Apr

2012

92.1

18.2

11.9

1.8

0.03

29-30-Mar

2013

91.3

18.4

9.8

2.0

0.25

23-Apr

Mean

72.1

19.1

9.9

1.8

0.1

20-Apr

Max

92.1

22.4

11.9

2.5

0.3

28-Apr

Min

54.0

16.2

8.3

1.2

0.0

29-30-Mar

* 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.

 

Gala Maturity Report 2008-2013

 

 
Year

Red Color (%)

Firmness (lbs)

Soluble Solids (ºBrix)

Starch-iodine Index (1-8)*

Ethylene (ppm)

Bloom Date

2008

93.5

18.3

13.6

5.6

21-Apr

2009

86.8

17.5

13.4

4.5

22-Apr

2010

78.0

16.3

14.9

6.4

9-Apr

2011

77.5

19.4

13.7

4.9

19-Apr

2012

91.1

18.0

13.2

4.1

7.13

29-30-Mar

2013

91.1

18.0

12.4

5.4

1.71

23-Apr

Mean

86.3

17.9

13.5

5.2

4.4

15-Apr

Max

93.5

19.4

14.9

6.4

7.1

23-Apr

Min

77.5

16.3

12.4

4.1

1.7

29-30-Mar

* 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.

 

Empire Maturity Report 2002-2013

 

 
Year

Red Color (%)

Firmness (lbs)

Soluble Solids (ºBrix)

Starch-iodine Index (1-8)*

Ethylene (ppm)

Bloom Date

2002

42.0

25.3

10.4

2.1

2003

60.4

21.9

9.6

1.7

2004

78.1

17.2

10.9

2.2

2005

55.3

20.3

10.1

1.9

2006

46.0

19.7

10.7

2.1

2007

64.0

17.9

10.6

2.1

2008

66.3

18.2

11.0

2.1

21-Apr

2009

52.4

16.6

10.9

1.1

20-Apr

2010

44.3

18.1

10.7

1.8

2011

49.8

19.7

11.2

2.0

2012

85.9

19.2

12.5

1.7

0.01

29-Mar

2013

63.0

18.6

10.6

1.5

0.04

21-Apr

Mean

59.0

19.4

10.8

1.9

0.0

15-Apr

Max

85.9

25.3

12.5

2.2

0.0

21-Apr

Min

42.0

16.6

9.6

1.1

0.0

29-Mar

* 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.

 

Maturity Report – Other Varieties 2011

Cultivar

Red Color (%)

Firmness (lbs)

Soluble Solids (ºBrix)

Starch-iodine Index (1-8)*

HoneyCrisp

66.2

15.8

13.0

5.1

Idared

17.0

19.9

11.1

1.2

* 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.

Maturity Report – Other Varieties 2012

 

 

Cultivar

Red Color (%)

Firmness (lbs)

Soluble Solids (ºBrix)

Starch-iodine Index (1-8)*

Ethylene (ppm)

Bloom Date

Fuji Early Strain

65.5

16.7

14.7

4.1

0.03

5-Apr

Fuji Late Strain

26.0

20.9

12.1

2.1

0.03

5-Apr

Idared

36.7

17.0

12.3

1.3

0.00

2-Apr

Rome

39.8

22.5

12.3

1.5

.

12-Apr

York

41.8

22.4

10.7

1.0

0.00

3-Apr

* 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.

Maturity Report – Other Varieties 2013

 

 

Cultivar (number of orchards tested)

Red Color (%)

Firmness (lbs)

Soluble Solids (ºBrix)

Starch-iodine Index (1-8)*

Ethylene (ppm)

Bloom Date

Cameo (1)

33.5

18.1

10.2

1.7

0.53

N/A

Fuji Early Strain (2)

80.3

16.3

13.6

4.3

1.51

25-Apr

Ginger Gold (2)

3.9**

16.0

12.8

3.5

0.00

24-Apr

Idared (6)

41.1

17.5

10.1

1.2

0.12

23-Apr

Jonagold (1)

35.5

18.7

11.8

2.8

0.00

23-Apr

Rome (1)

21.2

24.6

9.2

2

0.00

1-May

York (1)

53.5

24.4

9.4

1

1.20

25-Apr

* 1 = 100% starch, 5 = 60% starch, 8 = 0% starch.
** 1 = green, 2 = light green, 3 = yellowish green, 4 = yellow.

Harvest Maturity Report for August 20

Starting last week, we have been testing the maturity of various apple cultivars at our research farm. With the unseasonably cool weather over the past 10 days, particularly the night temperatures, red color is developing very nicely in many cultivars. Growers in the Winchester/Frederick County area have been picking Ginger Golds since last week, and some spot picking of Gala and Honeycrisp has begun this week.

The below linked pdf contains the fruit maturity data to date. Due to differences in location, soils, rootstocks, strains, etc. these data may not represent the fruit maturity in your own orchards.

Please see my previous posts about maturity indices, predicted harvest dates, and pre-harvest drop treatments for more information.

2013 Maturity Report Aug 19

Reducing pre-harvest drop, extending harvest timing, and increasing storage life

Three chemicals are available for reducing pre-harvest drop, extending harvest timing, and increasing storage life:

1) Aminoethoxyvinylglycine, AVG (ReTain)

  • Delays maturity and thus fruit drop by inhibiting ethylene production.

2) Napthaleneacetic acid, NAA (Fruitone N, Fruitone L, PoMaxa)

  • Decreases abscission of the fruit stem from the bud but can advance maturity especially when used at high rates or with repeated applications.

3) 1-Methylcyclopropene, 1-MCP (SmartFresh, Harvista)

  • Blocks the ethylene receptors, thereby preventing the autocatalytic climacteric process of fruit ripening.
  • SmartFresh is used in storage rooms on pre-climacteric fruit.
  • Harvista, the sprayable formulation of 1-MCP, is not yet commercially available for growers in Virginia.

Below are some suggested strategies for using ReTain and or NAA in your orchards this year. Applications should be based upon the predicted harvest date for each cultivar.

  • 1) ReTain (AVG) applied alone
  • Used at 1 pouch/acre [333 g (50 g a.i.) or 11.7 oz]. Apply to full coverage (~100 gal/acre). Use with an organosilicone surfactant (e.g. Sylgard 309 or Silwet L-77). Allow at least six hours of drying time. ReTain has a 7 day PHI.
  • For single pick cultivars, apply ReTain four weeks ahead of anticipated harvest date.
    • Standard approach for single pick varieties—reduces fruit drop and delays the harvest period by reducing ethylene production. Can also allow more time for the fruit to color on the tree.
  • For multi-pick varieties (e.g., Gala and Honeycrisp), apply ReTain one to two weeks ahead of the first harvest date.
    • Will not delay maturity, of the first harvest, but will do so for the later picks.
    • Ethylene suppression effect can last for up to 4 months in regular air storage.

2) NAA applied alone

  • Use at 10-20 ppm. High rates (>= 20 ppm) may advance maturity and reduce storage life. See the 2014 Spray Guide for cultivar specific recommendations.
  • Do not make more than two applications per year.
  • Do not apply more than at 3X concentration.
  • Organosilicone or nonionic surfactants are recommended.
  • Don’t tank mix NAA with calcium (a water conditioner might be needed if you have hard water).
  • Use maturity indices (starch rating) and limb tapping to determine timing.
  • Takes 2-4 days for the material to become active in the tree.
  • Apply single applications at 14 to 5 days before harvest; or two applications between 10-14 and 5-7 days before harvest.
  • Or use the branch tap method to decide when to apply NAA
    • As you get close to harvest, firmly strike a 3-4” diameter branch with the palm of your hand.
    • Do this on a daily basis.
    • If more than two fruit per limb fall, then apply NAA or consider harvesting within the next few days.
  • Single applications last about 7 days; split applications (two 10 ppm applications about five days apart) last about 12 days. Fruitone L has a 2 day PHI; PoMaxa has a 7 day PHI.
  • For apples that produce a lot of ethylene, NAA alone may not provide sufficient drop control. This is especially true in hot, dry years.

3) Combined sprays of ReTain and NAA

For the past several years, I have been evaluating the combination of ReTain with NAA at various timings and rates on Red Delicious, York, and Rome. Analysis of these experiments is still underway, but my initial assessment is that the combined sprays are especially effective at reducing pre-harvest drop while not reducing storage potential especially in hot, dry years.

When ReTain (AVG) was tank mixed with NAA, I found decreased ethylene production in stored fruit, and increased fruit quality (firmness–though differences were often 1 lb pressure or less). Additionally, the closer ReTain is applied to harvest, the better the fruit quality in storage. By using both materials (AVG and NAA), growers have the option of improving drop control without losing storage potential.

Some of my treatments included:

  • ReTain (full-rate) at 4 weeks before harvest, followed by NAA (10 ppm) at two weeks before harvest. (Provided good drop control and storage life.)
  • ReTain (half-rate) at 4 week before harvest, followed by NAA (10 ppm) at two weeks before harvest. (Provided good drop control and storage life, but did not extend harvest window or storage life as long as using the full rate.)
  • ReTain (full-rate) at 2 weeks before harvest, plus NAA (10 ppm) at 2 weeks before harvest. (This provided the best drop control and storage life.)
  • ReTain (half-rate) at 2 weeks before harvest, plus NAA (10 ppm) at 2 weeks before harvest. (This was not as effective at reducing pre-harvest drop compared to the full rate, but is a cost effective option when treatment is needed on a large acreage.)

I suggest growers consider the market destination for their fruit prior to applying either ReTain or NAA. With the multiple combinations and permutations of chemistries, rates, and timings, growers can manage harvest date, fruit drop, and storage quality with a fair amount of precision.  While combined ReTain and NAA applications are effective at decreasing pre-harvest drop, this approach is not necessary for all cultivars, storage plans, or market destinations.

Here are some examples: For apples that are going to be sold through direct markets, NAA alone may be sufficient to prevent drop. However, PYO operations may want to consider ReTain to delay the harvest of early ripening cultivars until the peak apple picking crowds arrive in September. For apples that are going to be treated with SmartFresh, the additional ethylene suppression from ReTain may not be necessary, and NAA alone might be sufficient to reduce pre-harvest drops. For growers who have significant acreage of a single cultivar, or who have multiple cultivars that overlap in harvest timing (or otherwise expect to have limited labor available for harvest), applying ReTain to part of the orchard can help delay harvest and stretch out harvest window.

For additional reading, Dr. Duane Greene (University of Massachusetts) recently wrote this article about his experiences with pre-harvest drop materials.