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Pomegranate (Punica granatum) is a specialty crop now grown on more than 10,000 acres in California. Pomegranate production has increased for both fresh market and juice in the last several years, and with this increase, random internally rotted fruit has become more noticed. The outside of the fruit looks perfectly fine, but internally the fruit is rotted and the arils (the flesh covered seeds that are eaten and juiced) are black. Pretty disgusting. Some fruit recently has shown up at harvest and the grower was unaware of the problem until the fruit was opened by a customer. The only difference between good fruit and affected fruit is that the blackhearted fruit is a bit lighter in weight. The absence of external symptoms makes the diagnosis of the disease very difficult, and consumers encountering the disease may change their perception of the pomegranate's many health benefits.
Initially, it was thought that the disease was caused by various fungi that can decay only the arils. However work by Themis Michailides from UC Kearney REC has shown that after inoculation of pomegranate flowers and developing fruit that the main cause of black heart is Alternaria spp. These fungi are very abundant in nature and cause diseases in a multitude of crops. Another fungus that is also isolated from pomegranate with black heart is Aspergillus niger. However, the decay caused by A. niger is softer than that caused by Alternaria and results in exuded juice. In addition, another major difference between black heart caused by Alternaria spp. and that caused by Aspergillus is that the latter decays both arils and rind of fruit and frequently symptoms reach the outer surface of fruit, which helps in the diagnosis of the disease. Inoculations with Alternaria spp. reproduce the typical symptoms of black heart (internal decay of the arils without any external symptoms).
Inoculations periodically with Alternaria spp. showed that most of the infections occur at bloom time and that spores of the fungus that are introduced into the fruit (puncturing from thorns, hemipteran feeding like aphids and stink bugs, or cracking) can result in black heart. The current research focuses on the identification of the various species of Alternaria that cause black heart, the understanding of the infection process, and the development of procedures to manage the disease.
Alternaria alternata and related species commonly occur on plant surfaces and in dying or dead tissues of plants. The pathogens overwinter on plant debris in or on the soil and in mummified fruit. The spores are airborne and can be carried to the flowers with soil dust. Infections may also start from insect and bird punctures on fruit. Research in the San Joaquin Valley showed that the petal fall stage seems to be the most susceptible stage when most of the infection occurs. However, infection can occur throughout the long bloom and fruit development periods.
Estimated losses are usually less than 1% but can be up to 6%.
So how does a grower reduce black heart? Fungicide coverage has been a problem for bloom fungicides, but Michailides has shown some promising new materials. Good orchard management practices, such as dust control and sanitation (removal of old fruit and dead branches), may reduce the incidence of the disease. Infected, healthy-appearing fruit may be dropped to the ground by gently shaking the tree at the time of harvest. Avoid water stress and overwatering that may result in fruit cracking.
Thorough sorting and grading of pomegranates for discoloration and cracking can help avoid packing diseased fruit.
See the Themis' slide show:
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To help people prepare, CAL FIRE has a checklist for evacuation online at http://www.readyforwildfire.org/Evacuation-Steps. UC Agriculture and Natural Resources scientists contributed to the research behind the recommendations.
A one-page checklist online at http://disastersafety.org/wp-content/uploads/2016/07/IBHS-Wildfire-Last-Minute-Checklist.pdf, also based on research by UC ANR scientists, is available from the Insurance Institute for Business & Home Safety.
Napa County residents have been told to be prepared in case they need to leave.
“We have team members tending to their own homes and or family's needs, providing support in shelters, and being available for immediate clientele needs in any way they can,” said David Lewis, UC Cooperative Extension director in Napa and Marin counties. “We look forward to calling upon UC colleagues with more experience to support our communities in the long recovery period. For the immediate future, we will stay focused in our efforts to support evacuation and shelter efforts – personal safety and needs are priority one until the fires no longer pose a threat.”
The main thing to remember when preparing to evacuate is to protect your life first.
“Don't die trying to prepare your house before you leave,” said Yana Valachovic, UC Cooperative Extension director and forest advisor in Humboldt and Del Norte counties. “Monitor the situation, watch the wind directions, and listen to all emergency personnel.”
To receive timely updates on fire conditions, Brian Oatman, UC ANR Risk & Safety Services director, uses Nixle. “While some communication methods may not work due to outages, the more sources we have, the better the chance that the message gets through,” Oatman said. To sign up for text alerts, visit http://www.nixle.com or text your zipcode to 888-777 to opt-in.
“We have coordinated with CropMobster to create a resource list at https://sfbay.cropmobster.com/bay-area-fire-resources where anyone can post any needs or offer help of any kind,” said Stephanie Larson, UC Cooperative Extension director in Sonoma County. “UCCE Sonoma has also created a Disaster Recovery for Agriculture Operations at http://cesonoma.ucanr.edu/Disaster_Resources for homeowners and managers of rangelands. UCCE is working closely with Sonoma County to provide UC ANR resources to assist with the recovery of our community that has been devastated by this fire.”
In Yuba County, the Cascade fire is 45 percent contained as of Oct. 12. “Evacuation orders are being lifted in parts of Yuba County,” said Janine Hasey, UC Cooperative Extension director for Sutter and Yuba counties. “Kate Wilkin, our new UC Cooperative Extension forestry, fire science and natural resources advisor in Sutter, Yuba, Butte and Nevada counties, has assembled resources for residents who are returning to their homes at http://cesutter.ucanr.edu/Fire_Information. We will be updating the website with more recovery information in the coming days.”
You may have missed it, but today (Thursday, Oct. 12) is National Farmers' Day. The day originated...