Select pumpkin varieties for disease resistance, eVGN January 2013

Although there are approximately 30 virus diseases of pumpkin reported worldwide, only four or five virus diseases are considered to be problematic in the mid-Atlantic. These include watermelon mosaic virus (WMV, formerly called WMV-2), papaya ringspot virus type W (PRSV-W, previously called watermelon mosaic virus 1 or WMV-1), zucchini yellow mosaic virus (ZYMV) and cucumber mosaic virus (CMV).

Recently, virus host resistance in pumpkin has become available in a few cultivars. In order to benefit from the use of the new cultivars, growers need to know what virus diseases are present in their area. However, identification of pumpkin virus diseases is difficult because the diseases cannot be identified reliably by their symptoms. CMV, PRSV-W, WMV and ZYMV may exhibit different symptoms at times, and at other times have overlapping symptoms.

Mixed infections also may yield unusual symptoms. Previous surveys throughout the eastern United States indicated that the most prevalent cucurbit viruses vary both temporally and geographically. We conducted a survey throughout Maryland and Delaware in 2008 and 2009. The objective of the survey was to determine the prevalence of virus diseases on pumpkins in Maryland and Delaware to assist pumpkin growers in selection of cultivars with virus resistance.

In both years, the most common virus disease in Maryland and Delaware was WMV. ZYMV was also prevalent in 2008 and PRSV in 2009. To benefit our region, cultivars should have a minimum of WMV resistance. ZYMV and PRSV resistance would also be beneficial in our region.

Magician is resistant only to ZYMV, and in the past has often developed severe virus symptoms in our region.

Hollar Seeds and Seigers have introduced Corvette, which has tolerance to both WMV and ZYMV. Outstanding Seed Co. has introduced Triumph, which has intermediate resistance to WMV, PRSV and ZYMV.

Orange Bulldog, which was developed at the University of Georgia, is also available and has virus tolerance (virus not specified). These cultivars are not yet recommended due to lack of field testing. However, our survey results indicate that a cultivar with WMV and ZYMV tolerance, such as Corvette or Triumph, would perform well as far as reduced virus disease.

By Gerald Brust, Central Maryland Research and Extension Center