Question: My peaches look somewhat deformed on one end (almost flat), and many are splitting open at the seam. What is causing this and how can I prevent it?
Answer: What you are describing sounds like peach split pit. The fruit splits before ripening, which allows earwigs, dried fruit beetles and other pests to damage the fruit.
The reason is unclear, but is believed to be caused by cultural practices that promote rapid growth, such as excessive thinning or irregular watering during the pit hardening stage. Thinning too early or too much heat also may contribute to peach split pit.
To minimize peach split pit and other problems, apply good cultural practices, including the following:
* Provide fruit trees with consistent soil moisture. Water well before the trees begin to show stress. Avoid prolonged saturation and avoid watering near the trunk and lower branches as this promotes root and crown disease. Water around the drip line and beyond. Water deeply and infrequently.
* Thin at the appropriate time. Avoid thinning until after pits are mature and hard. After the fruit sets on the tree, it will enlarge to an inch in diameter and then go into a resting stage when there is little increase in size.
This stage will last a week or two, depending on the variety. This is when you thin the fruit. Thin them so that there is 6 to 8 inches between each fruit. Thin to 10 inches apart if there is very heavy fruit set.
* Fertilize annually with nitrogen during the growing season. You can apply nitrogen fertilizer in spring or split between spring and just after harvest. Follow package directions, and avoid using too much nitrogen. This can cause soft, poorly colored fruit with a decreased shelf-life and increased chance of being infested by pests.
Have a problem in your yard? University of California Cooperative Extension (UCCE) Master Gardeners are here to help. These trained and certified horticultural volunteers are dedicated to extending research-based, scientifically accurate information to the public about home horticulture and pest management. They are involved with a variety of outreach programs, including the UCCE Master Garden hotline, which provides answers to specific questions. You can reach the hotline at (714) 708-1646 or send e-mail to ucmastergardeners @yahoo.com. Calls and e-mail are picked up daily and are generally returned within two to three days.