Apr 8, 2016
Assessing fruit bud survival and crop potential

A series of advective freeze events have damaged fruit buds, and following an additional freeze this weekend, growers will want to assess crop potential. It can be discouraging to count the buds that didn’t survive the cold, so focus on bud survival by using a technique Jim Schupp adapted from strategies to adjust crop load at thinning time.

Peach bud survival

Compare the number of live buds to the number a fruiting lateral should carry based on the target yield per acre.

Peach trees are in full bloom in many orchards, while apple trees are at the tight cluster stage.
Peach trees are in full bloom in many orchards, while apple trees are at the tight cluster stage. Photo: Penn State University
  1. To get a good estimate, examine about 150 to 200 flower buds per variety per block.
  2. Collect one strong fruiting lateral (pencil thick and 24 to 32 inches long)  from each of two sides of 5 representative trees per block.
  3. Bring the fruiting laterals into a heated building, place them in buckets of water, and allow them to warm up.
  4. Count and record the total number of flowers and unopened buds on a branch.
  5. Examine the ovule in the center of each flower, and count the number that are healthy.
  6. Compare this number per fruiting lateral to your desired crop load. If, for example, you have 12 live flower buds on a fruiting lateral that should carry 3 peaches at harvest, then you have four times as many live flower buds as are required for a full crop.

Here is an example of how this technique was used following a 2014 freeze event.

Apple bud survival

Compare the number of live buds to the target number for the branch diameter, using an Equilifruit disk.

Photos: E. Winzeler
Photos: E. Winzeler
  1. Collect one 3/8 to 1/2 inch diameter branch from each of two sides of 5 representative trees per block. Select branches that have 20 to 30 flower clusters (at least 100 buds). Preferably, there should be no heading cuts on these branches, so this technique works best with tall spindle-trained trees.
  2. Bring the branches into a heated building, place them in buckets of water, and allow them to warm up.
  3. Dissect the buds and count the number of king and side bloom with live pistils.
  4. Measure the diameter of the base of the branch with an Equilifruit disk to determine the number of fruit needed on that limb to set a full crop. Compare the number of live buds to this number. If, for example, you have 30 live flower buds on a branch that should carry 6 apples at harvest, then you have five times as many live flower buds as are required to have a full crop.

Here is an example of how this technique was used following a 2012 spring freeze.

Tara Baugher and James Schupp, Penn State Extension

Source: Penn State Extension

For more information, please visit http://extension.psu.edu/plants/tree-fruit.


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