Viroid Found on Georgia Citrus

Ernie NeffDiseases


Hop stunt viroid (HSVd) was found on citrus in Georgia for the first time this year. University of Georgia Cooperative Extension warns that HSVd and other viroids could pose a threat to the state’s growing citrus industry in susceptible varieties.

Leaf samples were collected in May and June from 12 different citrus plants in two nurseries in southern Georgia. Nine samples were negative for HSVd, but the other three were positive. The positive samples were all taken from Citrus reticulata Dekopon. The sequencing results revealed that the positive samples were non-cachexia HSVd variants. There are different types of HSVd, called cachexia and non-cachexia variants. “Cachexia” means severe chronic illness, so the cachexia variants are much more dangerous. The non-cachexia variants typically do not cause damage.

Although only non-cachexia variants have been found, nursery stock infected with this viroid should still be destroyed to prevent spread. Georgia nursery producers and citrus growers should take appropriate precautions to prevent the spread of this viroid disease. Ensure that proper sanitization is used on citrus grafting and pruning tools. Further research is needed to determine the distribution of HSVd and its potential to impact commercial citrus production in Georgia.

Moving forward, growers may be advised to have their citrus plants tested for HSVd, particularly if using established plants as stock sources or if the citrus is not doing well. The Plant Molecular Diagnostic Laboratory (MDL), a fee-based lab service of the University of Georgia Department of Plant Pathology, is now providing HSVd testing for citrus growers in Georgia. The clinic can accept leaf samples taken from various citrus varieties. For best results, 10 to 12 young leaves should be sent. The MDL is also testing for nine other citrus viruses or viroids and several citrus bacteria, including those that cause citrus greening and citrus canker disease. More information about the tests is available here.

In the United States, HSVd has been found on many different grapefruit, orange and tangelo varieties. Symptoms include discolored and gumming inner bark, pitting (small holes) in stems, bark splitting (coming apart) and stunted growth. There are typically not leaf or fruit symptoms. Some citrus varieties are resistant to HSVd, but others, including tangerines and their hybrids, will show damage.

See a full report on the HSVd finds here.

Source: University of Georgia Cooperative Extension

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