Knowledgebase
Late freeze affect on Palisade peaches #871599
Asked June 04, 2024, 6:46 PM EDT
Mesa County Colorado
Expert Response
The freeze may have done some thinning for you, but here are our recommendations:
For quality fruit, thin peaches to six to ten inches between fruit prior to the fruit reaching one inch in diameter. If you wait too long to thin, the fruit will be small and not juicy. Thinning also helps control codling moth in apples, as the female moth likes to lay eggs between touching apples.
That is from our publication Growing Tree Fruit in Colorado Gardens
Below is an update from May from the CSU Western Colorado Research Center about the frost and I will forward you the latest update from the research center:
After the recent frost I have received some questions about damage expectations and whether to begin/proceed-with thinning. I expect there to be a highly variable amount of damage given location, cultivar, fruitlet size/phenology stage, and frost protection practices, so I don’t think there is a “one size fits all” answer. A lot also depends on how many fruitlets you had before this latest frost event. My general feeling is that we should be waiting as long as we are comfortable with before proceeding with thinning. How long to wait will depend on many factors, but where fruit set was already reduced by the April 7th frosts, there is less hurry to thin those fruit than where we have a full crop, since carbon resources will be split across fewer fruit. At WCRC-OM we lost most peaches during the April 7th frost, however we don’t seem to have too much more damage in peaches from this recent frost.
Here is one monitoring approach I would recommend to get a better handle on your damage in peach and apple.
- Flag a number of fruiting shoots, in both colder and warmer areas, different cultivars etc…
- Remove any fruitlets on flagged shoots that already are looking like they will be aborted or are <1/2 the size of the other fruit on the tree (these will likely be dropped soon so we don’t want to include them in this count)
- Count the number of remaining fruit on each of the flagged shoots
- After 10-14 days count the fruit again and see if any were aborted. (Hopefully after some 80 degree days the fruit will abort if they are fatally damaged)
- Also check for any growth abnormalities that would indicate there is damage somewhere in the fruit
- Hormonal signals from living seeds allow fruit to form normally. Any damage to some or all seeds will misshapen fruit if not kill the fruit outright.
- Damage to skin tissue can cause fruit to grow abnormally and have aesthetic defects like frost rings in apples. This will take some time to show because it won’t happen until the fruit grows and I don’t expect this damage will show just by cutting open fruitlets.
Cherries tend to show damage a bit differently. You may have seen what appear to be full blooms in the past only to find no fruit set. This is because damage that happens before cherry bloom can kill the ovary of the flower, but the flowers will continue to bloom with a dead ovary, which is unlike most fruits. This difference is likely because cherries are non-climacteric fruit. Similarly, they may be able to have a dead seed they won’t necessarily abort, but they may not continue to grow normally either. I would recommend cutting open some cherries to assess whether or not the seed is healthy or oxidized (brown).
For apples, you likely have a full fruit set to start with, even with significant damage you will likely still need to thin. Keep frost rings in mind and remember even one dead seed out of five in a fruit can reduce size and produce an abnormally shaped fruit.
My hope for peaches is that when we see minor oxidative browning within dissected fruitlets, some of these fruits might still survive. After that, I would just worry about proper fruit formation and growth. However, if damage is significantly brown it will surely produce too much ethylene and the fruit will abort eventually, probably expedited with warmer temperatures.