July 2, 2016

1 - If you did not thin your apple fruit crop, you can still do it, and do not worry about natural thinning that occurs in the stress of summer.

Yard and Garden July 2, 2016


I should have done this sooner, I know, but a couple of my apple trees (smaller trees planted a couple of years ago) are really heavy with apples and my lower branches are going to break. With it being this late date, what is the best way to thin and which should I thin. The bug affected ones first, right? How many should I leave in a cluster? - Or at this point, does it matter?

- Leigh M.


The fruit should have been thinned when they were smaller and the tree had devoted fewer resources to forming the fruit, but you can thin them now. Yes, remove the ones that are obviously attacked by codling moth first - you may not see all that are infested, but when you see fruits with emergence holes and frass (insect excrement) and you should remove them.

The apple trees will often self-thin to some degree in June. Self-thinning involves the dropping of surplus fruit with the onset of summer stress. Those affected by codling moth larvae are often among those dropped naturally. Codling moth infested apple fruits are not desired at harvest time, so remove any you see that have not dropped naturally.

A second consideration regarding fruit thinning is the location of the fruit on the branch. The further it is from the trunk and the thinner the branch holding it, the greater the chance for branch breakage. Removing the apples farthest out will reduce breakage. However, apples branches will often bend down and not break. Other apples, those in the clusters, should be thinned to one or two per cluster. Ideally there will be 4 to 6 inches between apples. I have seen clusters that looked almost like grape clusters left on apple trees, but the result was many smaller apples. When you harvest these smaller apples and remove the cores, you will have more work to do and less usable produce. If you thin the apple fruits you will have more usable flesh and a smaller percentage core per apple fruit.

Pick up all fruit that you thin and those that fall naturally to reduce potential problems with codling moth problems next year. You should also pick up any fruit that fall at the end of the season. You can be compost the apples from thinning or, but in any event, you should remove them from the vicinity of apple and pear trees.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


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