Citrus tristeza virus (CTV) is still present in Florida and can be transmitted to new trees, especially during brown citrus aphid outbreaks, according to the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS). A presentation about surveying for CTV was available at the UF/IFAS booth during Citrus Expo in August.
The presentation noted that switching to sour orange rootstock increases the potential of CTV infection and tree decline.
The brown citrus aphid is the most dangerous vector of the virus, which is the causal agent of several important citrus diseases, including decline and stem pitting. The virus thrives in the phloem of trees.
UF/IFAS researchers have conducted surveys to study the presence of CTV isolates in trees — the T-36 decline isolate, the VT stem pitting isolate and the T-30 mild isolate. In the survey, plants were collected from Polk, St. Lucie and Indian River counties. The researchers found CTV, including decline and stem pitting strains, in trees on sour orange rootstocks. Unknown strains were also found.
Researchers also used psyllids to survey for CTV. They noted that CTV is present in psyllids, which acquire the virus but don’t transmit CTV. Eighty-five percent of psyllids that were collected from Glades, Collier, Pasco, Orange, Hendry and DeSoto counties had CTV, including decline and stem pitting isolates.
ABOUT THE ISOLATES
The T-36 decline isolate has caused the loss of almost 100 million trees worldwide; only trees on sour orange rootstock are affected by tristeza decline.
The VT stem pitting isolate causes extensive pitting in the trunk and branches. It causes major disruption in the normal differentiation of cambial cells into wood and bark, stunting, and small and misshapen fruit. Long-term effects can be worse than decline. Researchers consistently identify mild stem pitting throughout Florida.
Source: University of Florida Institute of Food and Agricultural Sciences
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