MSU Extension Apples

This is the 12th maturity apple maturity report for 2022. Reports are sent out every week (usually on Wednesdays), following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning.

This week in the Grand Rapids area, later season varieties are being harvested or are nearly mature, including Fuji, Rome, Braeburn, Pink Lady, Granny Smith, and Evercrisp. Overall, fruit size is very good, crop load is excellent, and red color is developing very well. Sugars and pressures have generally been a bit low this season compared to past seasons, likely due to the significant rainfall leading up to harvest. Crop and fruit size has been exceptional, as predicted.

Weather over the past week in the Grand Rapids area has been very cool and rainy, slowing down harvest a bit. High temperatures have been in the 50 Farhenheit and low temperatures in the mid- to upper-30s F. These temperatures have been 2-4 degrees cooler than average for this time of year. Persistent rainfall has been the theme of the past week, with a quarter to half inch or more recorded in many places each day. Over 2.5 inches of total accumulation was recorded at many Enviroweather stations throughout the region this past week. Despite the very cool temperatuers, we have NOT had many reports of freezing or cold injury in fruit, although there have been reports of chilling injury in Honeycrisp farther north that likely reached colder temperatures while fruit was still on the trees.

Expect a break from the cold, wet weather in the coming days. After Tuesday’s rainfall, expect conditions to be fair and dry. There is a very low chance of rainfall for the next week. Beginning Thursday, temperatures are expected to warm gradually to highs in the 60s F and then 70s F lasting through the weekend and the early part of next week. Afterward, a return to cool, rainy conditions is likely. 

Chilling conditions. Temperatures again this week fell to the low 40s F and upper 30s F. These temperatures have the potential to cause chilling injury in sensitive varieties. Temperatures for potential Honeycrisp chilling injury begin around 37 F and are likely at 34 F. Other sensitive varieties include Jonathan, McIntosh, and Empire. 

Chilling potential is based on research conducted by Randy Beaudry, summarized in this article about cool, fall nights and challenges for fruit storability. In general, Beaudry’s research found that fruit that sustained two nights of low temperatures experienced more chilling injury. This suggests that “low field temperatures slightly enhanced fruit sensitivity to chilling in storage.” In addition, “conditioning reduced chilling, ReTain increased the incidence of chilling, storage at 32 F (compared to 37 F) increased chilling injury, and conditioning increased bitter pit incidence.” Lower lying blocks, where cool air pools are at higher risk. Forecasts indicate there is the potential for chilling temperatures again this week, with the lowest temperatures predicted for the weekend.  

This article from Penn State University addresses concerns about lower temperatures. Fruit exposed to sustained low temperatures will be more affected, while fruit exposed to marginal temperatures for a night or two are likely to have injury. The work done by Jim Schupp found that fruit exposed to four hours or more of 28 F or lower are more likely to develop cold injury. Fruit exposed to marginal temperatures for only a night or two may recover, but will not be good candidates for long term storage as fruit may soften rapidly. Frozen fruit may also sustain flesh browning. “Fruit that were fatally frozen will exhibit flesh browning after thawing once the temperature has risen far enough for oxidation to take place. This browning can appear at the skin surface or below, and generally takes 24 hours to appear, longer if temperatures remain cold. After the apples have warmed enough to exhibit flesh browning, cut fruit open and inspect them. If browning appears, the fruit is obviously unfit for use.” 

Avoid handling frozen fruit. As a reminder, frozen and wet fruit will bruise more easily during harvest and transport. If fruit is lightly frozen, it will thaw much better on trees. Cut fruit to make sure they are thawed throughout, and not just the frost from the surface of the fruit. Do not leave bins in the orchard if freezing temperatures are expected.  

How to read maturity tables

***The majority of fruit were sampled from untreated blocks (no ReTain or Harvista applied). However, a couple of samples this week included fruit that were treated, as it is becoming more difficult to find untreated fruit.***

Each week, we test apple varieties that are nearing maturity in the Grand Rapids. We are reporting average values for several samples for each variety. Maximum and minimum values are included for the highest and lowest individual fruits evaluated for each, to give a full spectrum of the maturity. All samples included in the reports have been untreated with ReTain or Harvista, unless otherwise noted.

• Predicted apple harvest dates for 2022 from MSU
• More information on harvest management tools and timings can be found in this article.
• Guidelines from MSU to check for apple maturity in your own orchard, including specific pressure and starch recommendations by variety.
• Predicting apple maturity and starch chart from Cornell University
• Starch chart for Honeycrisp Apples developed by Washington State University.

Aztec Fuji

This variety is being harvested this week. Red color is very good in most locations. Pressures decreased a bit again this week, but fruit is overall still very firm, with samples averaging 16.4-17.6 lbs. Sugars are adequate although still lower than we see in some years for this high-sugar variety. Flavor of fruit was good in fruit we tested. Starch clearing indicates fruit is ready for storage, with averages between 5 and 6, depending on location. Watercore was observed in about half of fruit sampled this week.

Granny Smith

Fruit is mature or nearly mature. Pressure decreased a bit but is still very good, with samples averaging around 17 lbs. Sugars were similar to last week, but flavor has improved. Starch clearing is progressing, with averages for all samples near 3.5 this week. None of the fruit tested this week were producing significant amounts of ethylene.

Law Rome (predicted harvest date: Oct. 11)

Harvest is underway this week in many locations. Red color is excellent. Firmness is still very good, with samples averaging 19-20 lbs. Sugars improved a bit this week. Starch clearing was considerably more advanced, with most fruit at 4 or 5 this week. None of the fruit tested this week were producing significant amounts of ethylene. This variety is susceptible to red color bleeding in the flesh, and we observed this in about 25% of fruit tested this week.

Evercrisp

Fruit is mature and ready for harvest in some locations this week. Red color is good in most places. We have noticed that younger trees or trees with poor light tend to have poor or less bright color. Fruit is still very firm, with samples still averaging over 20lbs. Sugars improved again this week with averages of over 14 in all locations tested. Starch clearing is more advanced, 4-5 in most in fruit tested. A majority of fruit were producing significant amounts of ethylene. Recommendations from PSU are to harvest for long term storage at 4-6 and for direct market at 6-7 starch index. This variety has some sensitivity to CO2 injury in longer storage, which may cause internal browning. This is a very firm variety that stores very well and can benefit from some storage time, which allows for a little softening and development of aromatic flavor compounds.

Braeburn

Overall, fruit is nearly mature, and may be harvested next week. Red color is better this week, and background color lighter. Fruit was still very firm in samples tested this week, averaging approximately 18 lbs. Sugars are still a bit low. Starch clearing is continuing with most fruit tested near 3. A little less than half of fruit tested were producing significant amounts of ethylene.

Pink Lady

We sampled three blocks of standard Pink Lady (Cripps Pink) this week. Some locations are mature and being harvested this week, while others need a bit more time. Red color is very good in most places. Background color is still a bit green in immature fruit but faded to yellow-green in more mature fruit. Sugars were very good and varietal flavor excellent in fruit we tested. Fruit is still very firm, with most fruit over 19 lbs. Starch clearing is still just beginning in some places (1-3), more advanced in other locations (3-4). 

Apple maturity sampling parameters

• Ethylene (% fruits with internal ethylene over 0.2 ppm) = indicates when ethylene begins to influence fruit ripening and it cannot be held back easily after this is reached.
• Color % = the visual percentage of red color from 0 to 100; range is of all fruits tested. Indicates surface area covered in red and intensity of red color.
• Background color: 5 = Green, 1 = Yellow; range is of all fruits tested.
• Firmness in pounds pressure = measured with a Güss Fruit Texture Analyzer; range is of all fruits tested.
• Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.
• Starch For Honeycrisp: will typically be rated using the standard Cornell SPI scale (1-8). However, a separate starch chart for Honeycrisp Apples developed by Washington State University (scale 1-6) also exists.
• Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

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