Date: March 23, 2007
From: Tucson Citizen, Associated Press report (accessed Wed 25
Apr 2007) [edited]
<http://www.tucsoncitizen.com/daily/local/45844.php>
Growers and researchers in Yuma County are scrambling to find a
way to contain a virus that strikes melons and caused the loss
of an estimated 50 percent to 75 percent of the fall crop.
The virus -- _Cucurbit yellow stunting disorder virus_, or CYSDV
-- first appeared in Yuma in the fall [2006]. It attacks all
types of melons, plus squash, gourds, and cucumbers.
CYSDV symptoms develop first on older leaves and the plant
appears to need water. The leaves then yellow, and as the
plant's internal transport liquid system breaks down, it tries
to save itself by dropping older leaves. But without enough
leaves it can't support and nourish the fruit.
"It's devastating to melons," said Kurt Nolte, agriculture agent
with the Yuma County Cooperative Extension.
Researchers at the University of Arizona and agriculture
officials from Yuma, Imperial County, California, and Sonora,
Mexico, are working on ways to limit the spread.
The virus also has attacked plants across the border in Sonora,
Mexico
Yuma's fall melon crop is not very large, only about 800 acres,
Nolte said, but the spring crop now growing is estimated at 3000
acres.
Nolte said the source of the infection is unclear, but once
introduced it is spread from plant to plant by the whitefly.
"It's not a huge concern at the moment for the spring crop," he
said, because whitefly populations are low. But as temperatures
rise, insect activity picks up and the disease can spread.
Some commercial melon growers have volunteered to harvest early
and delay planting the fall crop to provide a "host-free"
period.
"We hope to break the cycle of the virus spreading from melon to
melon plant," Nolte said. But even with the voluntary host-free
period, the virus could survive in home gardens, or even on wild
melon varieties in the desert.
--
Communicated by:
J. Allan Dodds
Former ProMED-mail plant disease moderator
Professor of Plant Pathology
College of Natural and Agricultural Sciences
University of California
Riverside, CA 92521
USA
<dodds@ucr.edu>
[This is an attempt to control virus spread by limiting the host
plants of the whitefly vector _Bemisia tabaci_. Unfortunately,
whiteflies have a very wide host range of over 500 plant species
and weed species can serve as reservoirs. Whiteflies cause crop
damage by themselves but are also important vectors for a range
of serious
plant viruses, for example _Tomato yellow leaf curl
begomovirus_, _Tomato mottle begomovirus_, and _Bean golden
mosaic begomovirus_. Research into biological control of
whiteflies is being carried out.
A worldwide distribution map of CYSDV is available at
<http://www.eppo.org/QUARANTINE/virus/Cucurbit_yellow_stunting_disorder/CYSDV0_map.htm>
Pictures of CYSDV symptoms on melon can be seen at
<http://www.apsnet.org/online/feature/btabaci/image/whitefly19.jpg>
Links
Datasheet on CYSDV: click
HERE
1st news report of CYSDV in US:
<http://westernfarmpress.com/news/111306-melon-virus/>
NAPPO alert 11/06:
<http://www.pestalert.org/viewNewsAlert.cfm?naid=30>
Description of the genus _Crinivirus_:
<http://www.ictvdb.rothamsted.ac.uk/Ictv/index.htm>
Information on whiteflies (with pictures):
<http://creatures.ifas.ufl.edu/veg/leaf/silverleaf_whitefly.htm>
- Mod.DHA]
