Fruit Splitting in Navel Oranges

By Marian Stevens and Brent McGhie, Master Gardeners, 11-1-13

Splitting of green fruit on citrus trees, especially navel oranges, is a problem that shows up frequently in the Fall months.  Changes in climate, mainly variations in temperature and humidity, have more effect on splitting of navel oranges than anything else.  (And who would not agree that our weather has been especially variable recently?)   As the fruit gains and loses moisture, the rind does not expand as fast as the underlying flesh, and splitting occurs.  Most splitting occurs on navel oranges, starting near the stylar (or navel) end of the fruit where the rind is thin and at its weakest point.  Valencia oranges can also be susceptible to fruit splitting in some years if environmental conditions are particularly variable.  Potassium deficiency can cause rinds to be thinner, which can aggravate the problem.  The number of fruits affected varies from year to year, mostly depending upon the weather as the fruit matures. 

Although splitting is not known to result from any single factor, moderate cultural practices that avoid extremes in wet-dry soil moisture cycles and in nutrient levels should help to minimize the trouble.  To avoid these fluctuations, trees should be irrigated regularly, especially during hot, windy weather.  When hot and/or windy weather is anticipated, irrigate before this weather occurs.  Continue to irrigate lightly for a few days, and then resume a normal irrigation schedule.  For fertilization, instead of applying a single large application of quick-release fertilizer, smaller monthly applications through the Spring (February through May) may keep nutrient levels constant.  Timed-release fertilizers are a convenient way of supplying nutrients at an even rate, but they are more expensive. 

Although split oranges are edible, they are usually too green to be usable.  Damaged fruit should be removed and discarded, since they may harbor fungi, bacteria, insects and other unwanted pests                                                    

Do you have a question for the Butte county Master Gardeners?  Call our hotline, at 530-538-7201.