Peach problems

Question:

A good friend of mine here in Dona Ana County (south of Mesilla Park) has four or five peach trees that have been producing for two or three years. This year he encountered a problem that he had never had before, and one that I never experienced growing peaches back in Ohio. On the same branch, he had fruit of different sizes (a golf-ball size peach, two or three mature peaches, several more golf-ball peaches, etc.). This problem occurred on all the branches.

I found your name on the internet, and thought I'd ask you about this.
- Scott W.

Answer:

Growing peaches can be a challenge in New Mexico. The most common problems relate to insects. Your question is a new one for me. I called Dr. Ron Walser, NMSU Extension Fruit Specialist, about your question. He said this is actually a common problem if the winter is too warm. Peaches require sufficient periods with temperatures between 32 and 50 degrees F. to accumulate "chilling units" which are required to induce flowering and fruit formation. If the winter provided too little chilling, the embryo primordia inside the flowers may not develop properly. The result may be total failure of the plant to produce fruit, or the fruit may form; however, without an embryo and seed developing inside the fruit, hormones necessary for proper fruit development are absent. The result is a small fruit without a fully developed seed and kernel inside. Cut one of the smaller fruits open and you will probably see the undeveloped seed. Inside the normal-sized fruit you should find fully developed seeds with a normal pit and kernel inside the pit.

Dr. Walser also said that some varieties are more prone to this problem than others. Varieties that have low chilling requirements (those that require fewer hours in the 32 to 50 degree temperature) will be less affected. High chilling requirements increase the chance of this problem.

Another factor mentioned by Dr. Walser is that late frost in the spring, when the tree is flowering, can kill embryos. If the damage is only enough to kill the embryo, the fruit may continue to develop but never develop full size for the same reason mentioned above. Some fruit may not be affected, while others nearby are affected. This can explain the pattern of different-sized fruit on each branch.

When I asked Dr. Walser if the winter drought or the lack of precipitation in the early summer could have caused the problem, he replied that it was unlikely. Mild winters or late frosts are the most likely candidates for this. That is why you didn�t see it in Ohio. Ohio will have sufficiently long periods of cool temperatures to cause the flowers (and embryos) to develop properly.

Thank you for asking this interesting question.

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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.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

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