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Below you'll find a list of all posts that have been categorized as “Diseases”
By Evan Johnson The Florida summer rainy season is in full swing, and there have been one or two root flushes by now. This is a good environment for increases in soil Phytophthora propagule counts. High counts have been seen this year, especially in Southwest Florida. While much of the focus may be on root rot, it is important to …
Citrus canker has been detected in a residential area of Baldwin County, Alabama, which is bordered by Florida and the Gulf of Mexico. Federal and state plant health officials confirmed the identification of the disease from foliage and fruit samples collected by the Alabama Department of Agriculture and Industries’ (ADAI) routine citrus survey. This was the first detection of citrus …
By Megan Dewdney I did not need to visit my field trial to know that algal spot was in bloom on citrus in the last month. I have received many phone calls about it recently as growers notice the bright orange doughnuts on their tree limbs. For those unfamiliar with algal spot, it is a disease that occurs mostly on …
Scientists are hoping the RNA of an obscure infection can one day be used like a Trojan horse to deliver treatments to citrus trees, possibly to combat HLB disease. The infection, citrus yellow vein disease, was discovered 64 years ago in Riverside, California, and has never been seen elsewhere in the world. Decades later, University of California (UC) Riverside researchers …
Chris Oswalt details the connection between citrus leafminer (CLM) and citrus canker in the May/June Central Florida citrus Extension newsletter, Citrus from the Ridge to the Valley. He also offers some management tips. “I don’t think we can overstate the effect of leafminer damage on citrus foliage and the increased development of citrus canker lesions on damaged leaves,” the multi-county …
Researchers at the University of Melbourne have identified an Australian strain of fungus that causes citrus anthracnose. “Our research group at the University of Melbourne analyzed Colletotrichum collected from samples of anthracnose lesions on citrus leaves, twigs and fruit,” researchers Weixia Wang and Paul Taylor wrote. “The study identified six Colletotrichum species infecting Australian citrus. One of these is a …
Citrus researchers at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) are taking a more comprehensive look at how tools to manage HLB affect young trees. The goal is to develop integrated approaches and update management practices for growers. After one year of the research project, some interesting results are already emerging. The research project, “Establishing Healthy …
“When a tree gets infected, there is generally no way to cure it,” University of Maryland virologist Anne Simon wrote in a recent white paper about invasive tree diseases. She explained that trees lack adaptive immune systems, so once infected they typically must tolerate the pathogen for the remainder of their lifespan. “In some cases, immunity can be provided by …
University of Florida multi-county citrus Extension agent Chris Oswalt discussed fungal disease management in the April Central Florida citrus Extension newsletter. Here is a summary: In Florida, fruit fungal diseases that are oftentimes problematic in the early spring are melanose, scab and alternaria brown spot, along with citrus canker. In the summer period, greasy spot is more of a problem, …
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 …
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 …
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 …
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 …
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 …
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 …
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 …
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 …
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 …
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 …
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 …
