UC Delivers

New Virus Disease in Melons and Squash Is Identified and Described

The Issue

In 1991, silverleaf whitefly became a devastating pest of melon and squash crops, destroying 96% of Imperial County's fall melon crop and resulting in an estimated loss to growers of $12.5 million dollars. In succeeding years, the county's fall melon production dropped from approximately 12,000 acres annually to under 2,000 acres. In the late 1990's a related problem arose, a virus plant disease transmitted by the whitefly. This newly developing disease problem and management approaches to deal with it needed investigation.

What Has ANR Done?

In 1998, a team of UC Cooperative Extension and Agricultural Experiment Station researchers (Eric Natwick, Thomas Turini, Keith Mayberry and Robert Gilbertson) discovered a new geminivirus disease. The next year, a survey showed that the problem was widespread in cantaloupes in the Imperial Valley and Yuma Valley, but did not infect honeydew melons. In 2000, we identified the new cucurbit-infecting, whitefly-transmitted geminivirus and named it cucurbit leaf crumple virus (CuLCrV).

Host range studies at the UC Desert Research and Extension Center showed that CuLCrV infects most squashes, watermelons, cantaloupes and a few other melons as well as gourds, but did not infect honeydew melons, Crenshaw melons, casaba melons and several other melon types in the trial. Surveys of weeds, non-cucurbit crops and whitefly populations showed that (1) the CuLCrV is able to overwinter in the Imperial Valley, (2) weed species tested are not hosts of CuLCrV and (3) beans are a host. We also determined that CuLCrV is present in the Coachella Valley and Palo Verde Valley in Riverside County and Arizona. We determined that silverleaf whitefly is the vector of CuLCrV with the help of Dr. Wintermantel, USDA ARS, Salinas, CA.

The Payoff

Virus disease research helps growers with management decisions

Our research increased the awareness of squash growers, melon growers and pest control advisors (PCAs) about this new disease and how it is spread by silverleaf whitefly. As a result, growers and PCAs now know which melon and squash types and species are susceptible to damage from CuLCrV disease. Growers use this information in making important management decisions.

Contact

Supporting Unit: Imperial County

Eric T. Natwick, UC Cooperative Extension
UC Desert Research & Extension Center
1050 East Holton Road, Holtville, CA 92250-9615
(760) 352-9474 (Voice) (760) 352-0846 (Fax)