UC Delivers

UC research finds 7 more plant families that host cucurbit disease

The Issue

The whitefly-transmitted cucurbit yellow stunting disorder virus (CYSDV) infects cucurbits such as melons in several parts of the world. Infection can reduce crop yields. In 2006, CYSDV hurt cucurbit production in the low desert regions of California's Imperial, Coachella and Palo Verde valleys, Arizona's Yuma Valley and in nearby Sonora, Mexico. CYSDV infections were immediate and widespread among fall melon crops in 2006 and 2007 following heavy populations of the vector silverleaf whitefly. A cucurbit host-free period during the summer provided limited success in managing CYSDV, attributed mostly to fewer whiteflies in the Yuma Valley and central Arizona during July. Nearly all fall melon producers in Imperial County have chosen not to plant since 2007. Previous studies had shown that CYSDV was restricted to members of the Cucurbitaceae and lettuce as an experimental host, but we suspected other hosts were affecting the success of the cucurbit host-free period.

What Has ANR Done?

Eric Natwick, UC Cooperative Extension entomology advisor in Imperial County, and William Wintermantel of USDA Agricultural Research Service in Salinas, studied potential hosts in the desert melon production regions of California, Arizona and northern Mexico. They collected samples of possible non-cucurbit host plants from areas in and near melon fields in Imperial Valley. This study revealed a broader host range than originally believed for CYSDV, including the identification of non-cucurbit hosts that can serve as source plants for whitefly to transmit CYSDV back to melon and other cucurbits. At least one plant of the following species tested positive for the presence of CYSDV: alfalfa, snap bean, romaine lettuce, sowthistle, Wright’s ground cherry, silverleaf nightshade, alkali mallow, common mallow or cheeseweed, lambsquarters, redroot pigweed, five hook bassia and London rocket.

The Payoff

IPM strategy can be developed based on the expanded CYSDV host range

There were CYSDV hosts represented in seven new distinct non-cucurbit families. The demonstration that CYSDV can be acquired by whitefly vectors from non-cucurbit hosts and efficiently transmit the virus back to cucurbits illustrates the potential niche these plants may fill during seasons when melon and other cucurbits are not widely prevalent. The new information on additional non-cucurbit host families is now being used to develop CYSDV management strategies.

Contact

Supporting Unit: Imperial County

Eric Natwick, entomology farm advisor, 1050 E. Holton Rd, Holtville 92250 Cell (760) 996-1385, etnatwick@ucdavis.edu