The desert is no stranger to bad hombres when it comes to pests and disease, but this whitefly-vectored disease has the industry shaking in its boots wondering just how bad it could get. Cucurbit Yellow Stunt Disease Virus (CYSDV), which was rampant in spring melons in 2007, has now been confirmed in fall melons.

“The virus has been identified in fall melons in a field west of Wellton and another field in the Dome Valley area,” says Kurt Nolte, Yuma County Cooperative Extension agent. “We’re obviously very concerned about this development. It’s also been detected outside of Yuma County in Wenden and Maricopa. It appears to be spreading, but not as rapidly as last year. On the other hand, we weren’t really looking that closely for it last year.”

The sudden appearance of CYSDV has the industry scrambling to develop guidelines on how to stop it or at least slow the spread of the virus. A voluntary host-free period and the destruction of volunteer plants which preceded the fall planting may be partially credited with the relatively low incidence thus far. However, that remains to be seen.

“Our recommendations at this point are for growers to maintain a strong plant nutritional program and avoid stressing plants if possible,” says John Palumbo, research entomologist with the University of Arizona. “Also when practical, we suggest suppressing adult whitefly numbers in an attempt to minimize further spread of the virus.”

During the spring melon season, Sumerton was the epicenter of the virus, according to Nolte. “So far there’s been no known detection in that area this fall. That’s the good news. The bad news is that the fall melons in other areas that have been affected have been hit at a very young seedling stage. When the virus hits that early, the melons don’t have the reserves to withstand it as well as they might later on in the growth cycle.”