Harvest season is underway and growers should pay close attention to the instances of black-hearted pomegranates in their orchards. The fruit can appear to be healthy on the exterior, but inside the arils are black and rotted.
Ben Faber, UC Farm Advisor working in Ventura and Santa Barbara Counties, noted the disease is particularly troubling because it “produces a beautiful looking fruit with a heart of darkness in the center.”
Research on the cause of the disease has shown the main pathogens for black heart are Alternaria alternata and other Alternaria species, as well as Aspergillus niger. Most infections occur during bloom as spores entering the fruit from a puncture or crack, or as a result of pests such as aphids and stink bugs. Sanitation is important to limiting the inoculum source. “Fungal infections are spread from wounds and from diseased fruit and so you cut out diseased tissue, get rid of it and pick up all the mummies, anything that’s on the ground,” Faber said.
Unlike stone fruit suffering from infections such as brown rot in which symptoms are clear and apparent, diagnosis of an infected pomegranate is difficult because of a lack of external symptoms. Faber said that with instances of black-hearted pomegranates, “you don’t see the damage until the very end when you harvest it.”
Estimated losses caused by the disease can be as much as 6 percent. A grower can often be unaware of the presence of black heart until the fruit is opened by a consumer. A concern surrounding black-hearted pomegranates is the potential to alter consumer perception of the fruit, causing demand to potentially decrease.
Employing proper orchard management practices such as dust control and sanitation can reduce the occurrence of the disease. Fruit that has been infected can also be gently shaken from the tree and dropped to the ground during harvest. Researchers are continuing to work on developing procedures to better manage the disease.
Pomegranate production in California has picked up over the past several years, with over 10,000 acres planted throughout the state. Approximately 95 percent of the pomegranates grown are Wonderful variety. This year’s harvest appears to be somewhat lighter than normal, but the size and sugar levels appear to be good. California produces nearly all of the pomegranates that are grown domestically in the United States.