Geranium Virus Hard To Identify, Easy To
If those geraniums that looked so beautiful at the nursery last spring just
didn't bloom well or ever look healthy in your yard, they may have had a virus
"Viruses do not kill geranium plants, but some can severely reduce
vegetative growth by affecting leaves and can reduce flower quality and
marketability by deforming blooms and causing color breaks or streaks,"
says Agricultural Research Service plant
pathologist Ramon L. Jordan. A
plant virus expert, he leads the Floral and Nursery Plants Research Unit of the
Jordan says confusion exists about the exact identity of some of the 15 or
so different viruses attacking geraniumsa flower crop worth about $200
million a year to U.S. growers. Geraniums, genus Pelargonium, are one of
the most rapidly expanding garden crops in the United States.
Now Jordan, working with ARS plant pathologist
Gary R. Kinard, has developed new
tests that use biotechnology to detect two of the newer viruses: pelargonium
line pattern virus and pelargonium ringspot virus. The tests take about 24
Jordan says the new tests will help ensure that both exported and imported
geranium plantspotted or in bedsare free of the two viruses.
Over the last 18 years, Jordan has been pursuing and identifying
disease-causing viruses in ornamental plants, vegetables, and trees. What's
tricky about the geranium viruses, he says, is the easy way they get around and
the 1 to 3 weeks that it takes after infection for their symptoms to appear.
"An infected plant in the greenhouse can be the source of some viruses
that can spread via water to the plant sitting next to it," he says.
"Other viruses are spread by aphids, while tiny insects called thrips can
transmit viruses or carry infested pollen from infected plants to healthy ones.
"Since geraniums are propagated mainly by taking cuttings from
established plants, this is likely the most common method of virus
Jordan is working on the other viruses that attack geraniums, as well as
those that cause severe problems in such popular flowers as impatiens and
gladiolus. -- By Hank Becker, ARS.
Jordan is in the USDA-ARS Floral and Nursery Plants Research Unit, U.S.
National Arboretum, 10300 Baltimore Ave., Bldg. 010A, Beltsville, MD,
20705-2350; phone (301) 504-5646.