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 disease, allowing for rapid spread.
While all citrus varieties are susceptible to canker, some varieties are less susceptible than others.
Raj Singh, associate professor of horticulture at Louisiana State University (LSU), collaborated with the Louisiana Department of Agriculture and Forestry and the LSU AgCenter on a two-year study to determine which varieties of satsumas are most resistant to citrus canker. Satsumas dominate the citrus industry in Louisiana, accounting for 63% of the state’s total citrus acreage.
To accomplish his objectives, Singh evaluated healthy satsuma trees of different cultivars from 2018 to 2020. The trees are located in southern Louisiana at five locations known to have citrus canker. Both disease incidence and disease severity data were collected and analyzed to determine each variety’s susceptibility.
Based on data, Brown’s Select, Miho and Owari satsumas had consistently delayed onset of citrus canker with only 20% incidence by two to four weeks, according to Singh.
“Everywhere we’ve seen this disease, the younger tissue (when the leaf is still developing) is highly susceptible compared to when the leaf if fully mature,” Singh said during the virtual 2021 LSU AgCenter Citrus Symposium. “The delay also gives you a window of protecting those young, developing leaves with copper as a preventative treatment.”
Brown’s Select and Miho had the smallest average number of canker lesions per leaf, with approximately 1.6 and 1.5 canker lesions per leaf, respectively.
Currently, Singh is developing an Extension fact sheet to provide growers with more canker information.
Get canker management advice from the University of Florida here.