Citrus growers growing citrus trees on sour orange virus will have to look out for Citrus Tristeza Virus as well as citrus greening.

Citrus Tristeza Virus was once a major citrus pathogen, killing nearly 100 million trees worldwide, according to a Citrus Industry article. Causing a disease called Tristeza decline, the issue was mitigated by growing citrus scions on alternative tolerant rootstock other than sour orange rootstock; these alternative rootstocks can get infected by Tristeza decline but exhibit no symptoms. However, according to the article, many Florida citrus growers have decided to use sour orange rootstock due to citrus greening, meaning Citrus Tristeza Virus has the opportunity for a comeback. Explore the pathogen’s details below.

Details on Citrus Tristeza Virus

According to the article, Citrus Tristeza Virus is spread by four different aphid species, and neither spray treatments targeting aphids or those targeting the Asian citrus psyllid—the vector that spreads citrus greening—are effective at stopping the spread of Tristeza decline. The disease causes “phloem necrosis below the bud union,” per the article, reducing the sugars that get to the roots. Feeder roots die off; the resulting improper uptake of water and nutrients eventually kills the citrus tree. The symptoms are very similar to those of citrus greening; researchers are concerned growers will not be able to tell the difference, and Tristeza decline will spread once more.

Furthermore, the article maintains that grower assumptions that spraying targeting Asian citrus psyllids will control aphid populations are incorrect. Testing has shown that Tristeza decline is still present in Florida, and researchers caution growers against using sour orange rootstock.

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