Interesting I have never heard of this before

Turkey Creek

5 year old buck +
I must be overlooking something. I dont quite understand how this process works and to what temperature it is still effective. I guess I will need to do a bit more researching on the subject.

Setting apples with plant growth regulators

Recent cold injury requires consideration of Promalin or Perlan on frost-damaged apple sites.
Posted on May 9, 2017 by Amy Irish-Brown, and Phil Schwallier, Michigan State University Extension

Growers around the Ridge and in other areas of Michigan are currently assessing the frost damage from the cold overnight temperatures on May 7-8, 2017, and again on May 8-9. As of now, there appears to be some damage in many apple blocks, but the damage depends on the stage of development in each block, the variety and, of course, the elevation and frost protection methods used or available.

While there are cold-damaged fruits, there are still many with no visible damage. The flowers in the tops of trees are much less hurt than the lower parts of trees. There seems to be damage in low areas as expected with frosty conditions, but also some reports of higher levels of damage on the tops of hills.

In this situation, growers need to assess the potential of applying Promalin (Valent) or Perlan (Fine Americas) to frosted blocks. Promalin and Perlan are the same essential product from different manufactures. Both products are a mixture of naturally occurring plant growth regulators (PGR), most specifically gibberellic acid 4 and 7 (GA4+7), which cause cell enlargement. This PGR can impact apples in many ways depending on when it is applied.

In the case of apple trees that have been frosted, these gibberellins can stimulate parthenocarpic fruit development. Parthenocarpy is the natural or artificially induced production of fruit without fertilization of ovules. Fruit that develop through this method are seedless.

Much of the early research recommends applying Promalin/Perlan within 24 hours of the frost event. However, more recent studies have found that the application window is longer than the 24 hours, perhaps as much as four days. According to
Michigan State University Extension educator Phil Schwallier’s observations, he has seen this PGR work when applied within a few days after the frost event and still increase fruitset.

This product is best applied from pink to petal fall, which most apple flowers in the Grand Rapids, Michigan, area are in at this time. For apples in earlier or even later stages of development, how fruit will respond to GA4+7 is an unknown, but perhaps worth an application if flowers are not completely killed. The application can be made up to four days from the May 8 frost event, so growers will have a bit of time to determine the level of damage and their stage of development for each of their blocks.

As with other PGR applications, temperatures on the day of application are important, but the days following are even more critical. In the case of Promalin/Perlan to set fruit for this season, getting the application made by Wednesday, May 10, is highly recommended to take advantage of warming temperatures. You can start applying right away, but try to get it done by May 10.

Promalin/Perlan are recommended to be used at 1 pint per acre. In addition to setting fruit in frosty conditions, Promalin/Perlan will do the following:

  • Increase cell division.
  • Increase fruit weight.
  • Increase apple typiness.
  • Increase fruitset.
  • Start the thinning process.
You could add the Promalin/Perlan with your fungicide cover sprays, but be careful with other PGRs such as Apogee—leave at least two to four days between PGR applications.

Special thanks for MSU Extension’s Nikki Rothwell and Emily Pochubay for the use of their 2016 article on this topic from the Northern Michigan FruitNet Report – May 26, 2015.

This article was published by Michigan State University Extension. For more information, visit http://www.msue.msu.edu. To have a digest of information delivered straight to your email inbox, visit http://www.msue.msu.edu/newsletters. To contact an expert in your area, visit http://expert.msue.msu.edu, or call 888-MSUE4MI (888-678-3464).
 
Yeah i'm in MI, that was brutal, I have my Gala doing it's first bloom performance, it has 4-5 king blossoms open when the last 2 cold nights hit, they seems to be visibly unaffected by the 26 & 28 degree nights. Here is hoping....
 
Maybe I should have sprayed Promalin, I do have some on hand, to see if it would have worked. I am losing a lot of 6-7mm apple fruitlets now. Not sure sure why at this rate the tree will be bare in another couple of days. Not sure if the fruit wasnt really fertilized?

dropped apple fruitlets 1.jpg

dropped apple fruitlets.JPG
 
I read that too TC, I don't know much about their use either. We had some talks on frost control, they did mention using plant growth regulators, but did not spend a lot of time on it.

I guess you just need to asses a few things. 1) what possible cold/ frost damage you may have had. 2) what your blossoms looked like in bloom. 3) How was pollination??? Cold, windy, bees flying good?

I'm right in the middle of bloom season now, most right in bloom, some past, some in king. Thus far bee flight has been poor. We've had awful cold, wind, rain and snow, but have not gotten to cold. (28 degrees maybe) Today is supposed to be good.
 
Unfortunately 1-3 on your list could all be factors. I made the assumption that "healthy" looking fruitlets of that size wouldnt abort like they are at this stage of the game. I still have a lot to learn in the fruit production part of the game.

I did find a little more information regarding the use of Promalin, some from the manufacturers site and a couple of experiments. Looks like Promalin is only effective during a frost event up to petal fall. Promalin does not save all of the crop, seems like it boosted fruit retention to roughly 25% compared to non treated areas. Though 25% is a lot considering you might end up thinning a good percentage of your crop in heavy set years.
 
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Tough spring for everyone it seems. When was you petal fall? I would guess you just didn't have great pollination for whatever reasons. Have you done a soil sample lately. Check zinc, boron and K, all essential for bud development.

Also what did the anthers/stamen look like when the flowers opened? Vibrant yellow or were some tips brown? Sometimes you will see them on the brown side even when they first open. That's a sign of poor bud development,from cold temps at some point, or from lacking in something.
 
Now that you mention it I thought the color of the anthers and stamen was off. They didnt appear as bright yellow as I thought they should have been, possibly some brown when they first opened. I had some micronutrient issues in those trees last year. By the time I realized it and began corrective measures it was well into summer. Maybe that is part of it. We did have some cold weather just prior to flowering and during flowering so that could be part of it as well.
 
Generally, you are fertilizing, this year for next other than a flush of N. That could be it or a cold snap. Good thing to ponder though and keep tabs on.

Maybe you just got a good thinning!
 
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