West Lafayette, Indiana
April 6, 2007
The first confirmation of a new insect-borne watermelon virus in
Indiana is significant but is not cause for alarm, according to
a Purdue University plant
pathologist.
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Squash
vein yellowing virus |
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Whitefly |
The disease, squash vein yellowing
virus, was found in a commercial watermelon field in Sullivan
County in September 2006. It is the first time that the disease,
carried by the approximately 1/16-inch whitefly, has been
observed outside of Florida.
An article on the finding and virus identification by Dan Egel,
a Purdue Extension plant pathologist in the Southwest Purdue
Agricultural Center in Vincennes, Ind., is being published in
the journal Plant Disease.
"Whiteflies are not normally agricultural pests in Indiana
because they are a southern species," Egel said. "Winds can blow
them up from the south. They feed on watermelon plants and pass
the virus from plant to plant.
"Several strains of whitefly exist. The one that transmits
squash vein yellowing virus is strain B. The common greenhouse
whitefly has not been shown to be involved in the disease."
The disease can cause vine collapse, plant wilt and root rot. In
Florida, where the virus first appeared in 2002, the symptoms
have included discoloration of the fruit.
Egel and Scott Adkins of the U.S. Department of Agriculture's
Agricultural Research Service (USDA-ARS) in Fort Pierce, Fla.,
identified the disease found in Indiana as the squash virus
through DNA analysis.
The whiteflies that carried the squash virus to the Hoosier
state came late in the season. The disease caused moderate
symptoms, which were restricted to one farm, Egel said. Because
Indiana winters are cold, whiteflies can't survive over the
winter.
"It's unlikely that this disease will become a major problem in
Indiana since it's unusual for whiteflies to be here," Egel
said. "If the whiteflies did return, it would likely be late in
the season, too late to cause significant damage to the
watermelon crop, and then the insects would die over the
winter."
Similar diseases occur in Indiana, including mature watermelon
vine decline, which appears to be caused by a soil-borne
microorganism rather than an insect.
Growers should not be concerned about squash vein yellowing
virus, but they should be aware of it and of mature watermelon
vine decline. They also should be on the lookout for any
symptoms so the problem can be diagnosed, Egel said.
"There are a lot of questions about both diseases," he said.
"The main thing is we don't want producers to be alarmed. We
want them to understand the differences in the diseases and to
report any symptoms they encounter."
Egel is continuing to study watermelon diseases, focusing mainly
on mature watermelon vine decline since it's found regularly in
Indiana. The project is funded through a $98,500, three-year
grant from the USDA Sustainable Agriculture Research and
Education. Part of the research project includes a new
Southwest-Purdue Agricultural Center research greenhouse,
partially funded by the Illiana Watermelon Association and the
National Watermelon Promotion Board. |
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