The University of Arizona

Issue

Yuma County melon producers suffered crop losses of 60 percent or more to the whitefly-transmitted Cucurbit yellow stunting disorder virus (CYSDV) when it first appeared in 2006. Damages amounted to about $14 million. Yuma County produces about 75 percent of Arizona’s melon crop, including cantaloupe, honeydew, watermelon and mixed melons. The virus has now become established in the desert Southwest, requiring management to reduce crop losses.

What has been done?

Through a partnership between the University of Arizona’s Yuma Agricultural Center (YAC), Yuma County Cooperative Extension and local growers, a wide-scale whitefly and virus monitoring program was implemented in Yuma County, along with a voluntary host-free period during the summer to reduce whitefly infestations, and other strategies. The monitoring effort is based on results collected from 105 sticky traps spread in a uniform grid across 200,000 acres in rural and urban areas in the county. GIS software is used to produce maps showing the weekly dispersal of adult whitefly populations. The system can also pinpoint areas where virus symptoms have appeared.

Impact

The GIS maps have confirmed the benefits of a countywide, host-free melon period first implemented in 2007. The growers disked their spring melon crop in July—and any subsequent volunteer melons or other hosts—and waited 30 days before planting the fall crop in August. As the virus cannot live without a host for more than 7-10 days, hungry whiteflies disperse to other fields. The 2008 summer host-free period helped growers achieve a 20 percent reduction in the severity of CYSDV in the fall 2008 melon crop.

Contact

Kurt Nolte
(928) 726-3904
email:knolte@ag.arizona.edu

John Palumbo
(928) 782-3836
email:jpalumbo@ag.arizona.edu