Vaccinating Trees Against CTV and HLB

Ernie Neff Diseases

University of Maryland virologist Anne Simon and the company she founded, Silvec Biologics, have successfully vaccinated laboratory hosts against citrus tristeza virus (CTV). They are now focusing on HLB, also called citrus greening. The vaccination induces trees to produce their own therapeutic agents.   Silvec’s vaccination concept is based on the discovery of a novel infectious RNA that the company calls …

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Australia Declared Free of Citrus Canker

Ernie Neff Diseases, International

On April 12, Australia was officially declared free from citrus canker after the remaining restricted areas in the Northern Territory (NT) were lifted. The disease was not detected in commercial orchards in Australia and was restricted to non-commercial residences in Western Australia (WA) and NT. Minister for Agriculture, Drought and Emergency Management David Littleproud acknowledged NT and WA for their …

Plan Greasy Spot and Melanose Management

Tacy Callies Diseases, Tip of the Week

By Megan Dewdney Greasy spot and melanose are two fungal diseases that have long needed the attention of Florida citrus growers. While they are more of a concern for fresh fruit growers, trees for processing can be damaged, too. In terms of management priorities, greasy spot is the greater concern since it reduces tree photosynthetic capacity and causes defoliation. Melanose …

Plan Now for Phytophthora Season

Tacy Callies Diseases, Tip of the Week

By Evan Johnson The Florida citrus spring leaf flush is hardening off, which means the first root flush of the year is beginning. With the spring root flush comes thoughts of phytophthora foot rot. Spring roots are at particular risk in groves that had high phytophthora pressure last fall because many of the resting spores will start activating with the …

What to Do About Citrus Black Spot

Tacy Callies Diseases, Tip of the Week

By Megan Dewdney Citrus black spot is one of the newer diseases to worry Florida citrus growers. The fungal disease was first detected in Southwest Florida in 2010. The vast majority of finds have been in the southwestern citrus-producing counties of Collier, Hardee, Lee, Charlotte and Glades, but the disease has slowly moved northward. Black spot is still considered a …

The Search for Canker-Resistant Satsumas

Ashley Robinson Diseases, Louisiana

Citrus canker, a highly contagious bacterial disease of citrus, was first detected in Louisiana around 1914 and declared eradicated by 1940. However, the disease reappeared in the state in 2013. Right now, there are no effective treatments to eliminate the disease after the infection has occurred. Adding insult to injury, Louisiana’s hot and humid climate is especially conducive to the …

Prepare for Citrus Canker Season

Tacy Callies Diseases, Tip of the Week

By Evan Johnson Now that bloom has arrived, it is time to start thinking about canker management. As the fruitlets develop, they will become susceptible around the end of March to the beginning of April. The spring fruit lesions are particularly concerning because they cause fruit drop. Without proper management, early season canker can cause 90 to 100% crop loss …

Canker Treatment Uses Less Water and Copper

Tacy Callies Diseases

An important bacterial disease that affects citrus trees and causes lesions, citrus canker has been effectively controlled by spraying copper. However, standard management techniques involve spraying excessive amounts of copper and water without consideration for the size of the trees. “This technique resulted in a waste of resources as well as higher costs, detrimental environmental impact and risk for development …

Minimize Blemishes on Tangerines and Grapefruit

Tacy Callies Diseases, Tip of the Week

Megan Dewdney Since tangerines and grapefruit they are eaten fresh, a blemish-free peel is highly desired. Two diseases that frequently mar the peels of tangerines, and occasionally grapefruit, are Alternaria brown spot (ABS) and citrus scab. Both diseases cause symptoms on leaves and fruit. ALTERNARIA BROWN SPOTThe early foliar symptoms of ABS are small yellow flecks that quickly become larger …

Stem Pitting Disease Caused by Citrus Tristeza Virus

Tacy Callies Diseases

By Amit Levy, Peggy Sieburth and Ozgur Batuman When we hear or read about citrus tristeza virus (CTV), we usually think about the decline of sweet orange or grapefruit trees on sour orange rootstocks. However, there are other diseases caused by different isolates of the virus. One of these diseases is stem pitting, mostly caused by the VT isolate of …

Scout Early Bloom for PFD

Tacy Callies Citrus, Diseases, Tip of the Week

By Andre B. Gama and Megan M. Dewdney Postbloom fruit drop (PFD) of citrus is a disease caused mostly by the fungus Colletotrichum acutatum. This fungus survives by producing resting structures on leaves and stems. When flowers start to appear in groves, these resting structures produce spores that can cause PFD. However, the fungus requires specific weather conditions to be …

Foliar Disease Management in 2021

Tacy Callies Diseases

By Megan Dewdney There were many challenges in 2020, but fortunately the Florida season for foliar citrus diseases was relatively normal. Little to no postbloom fruit drop (PFD) was reported during the 2020 bloom because of a sudden dry spell as the flowers opened. As spring 2021 approaches, the forecast is for a La Niña weather pattern with slightly warmer …

Sneak Peek: February 2021 Citrus Industry

Tacy Callies Diseases, Sneak Peek

While everyone strives to protect themselves from coronavirus disease, growers have an additional concern: protecting their trees from citrus disease. While HLB is of course the most damaging disease of citrus, there are other diseases that should not be overlooked. Disease management is the theme of the February 2021 issue of Citrus Industry magazine. University of Florida Institute of Food …

Citrus Diseases to Pay Attention to

Tacy Callies Diseases

Phytophthora and leprosis diseases can each substantially reduce productivity of a citrus tree, but when they attack trees already weakened by HLB, the result can be fatal. Ozgur Batuman, assistant professor at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), explained how co-infection impacts HLB-infected trees during a recent UF/IFAS webinar. PHYTOPHTHORA DISEASESPhytophthora species are soil-borne fungal pathogens …

Georgia Citrus Pest and Disease Update

Tacy Callies Diseases, Georgia, Pests

As the Georgia citrus industry continues to grow and prosper, growers should be aware of the potential signs of citrus pests and diseases that could be looming in their groves. Bill Barber, Certified Crop Advisor and owner of Barber Ag Services, delivered a presentation during the 2021 virtual Southeast Regional Fruit and Vegetable Conference. He addressed pests and diseases presently …

Spotting the Symptoms of Citrus Black Spot

Ernie Neff Diseases

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Extension recently provided the following information about identification of citrus black spot (CBS): Fruit symptoms can be observed around this time of year with the onset of color break and fruit maturity. Growers and agricultural workers should learn to identify the symptoms of CBS even if they are not located …

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Black Spot Likely in More Florida Counties

Ernie Neff Diseases

Although citrus black spot has only been detected in commercial groves in five Southwest Florida counties, it is still spreading and likely to be in additional counties, according to plant pathologist Megan Dewdney. The five counties with detections are Charlotte, Collier, Glades, Hendry and Lee. Dewdney is a University of Florida Institute of Food and Agricultural Sciences associate professor at …

Emerging Trunk Disorders

Tacy Callies Diseases

By Evan Johnson and Megan Dewdney The last two years have seen increasing grower questions and reports of citrus trunk disorders in Florida. Sometimes these reports are associated with sudden tree collapse. In many cases, phytophthora foot rot is initially suspected. Typically, the symptoms don’t quite match those of foot rot, and phytophthora cannot be isolated from the lesion. If …

Citrus Advisory System Provides PFD Alerts

Ernie Neff Diseases

Beep. Beep. Beep. That’s the sound of an alert telling a citrus grower it’s time to spray fungicide to help prevent fruit from falling off the tree due to postbloom fruit drop (PFD). University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers have developed a Citrus Advisory System (CAS) that sends web-based alerts to growers via mobile devices. …

Stem Pitting Could Develop in Florida Citrus

Ernie Neff Diseases

Citrus tristeza virus (CTV) stem pitting, which causes severe problems in Asia and other places, could develop in Florida, according to plant pathologist Amit Levy. The University of Florida Institute of Food and Agricultural Sciences researcher at the Citrus Research and Education Center discussed the disease at this year’s virtual Citrus Expo. Noting that “early detection is essential,” Levy said …