University of Maryland Extension

Presence of Cucurbit Virus Diseases in the Mid-Atlantic

Dr. Kathryne Everts - UME-PSLA, Dr. Karen Rane - UM-Plant Diagnostics Lab, Dr. Gerald Brust - UME Specialist, Barbara Scott and Mark VanGessel - UDE


Kathryne L. Everts, University of Maryland, Plant Science and Landscape Architecture, Salisbury, MD 21801

Karen Rane, University of Maryland, College Park, MD

Gerald Brust, University of Maryland Extension, Upper Marlboro, MD

Barbara Scott and Mark VanGessel, University of Delaware Research and Education Center, Georgetown, DE.

Additional index words: Cucurbita pepo, Pumpkin



There are approximately thirty virus diseases of cucurbits reported worldwide (Kyle, 1993). However, the primary pumpkin virus diseases in the mid-Atlantic region of the United States are cucumber mosaic virus (CMV), papaya ringspot potyvirus type W (PRSV-W, which was previously called Watermelon mosaic virus 1 or WMV-1), Watermelon mosaic potyvirus (WMV, which was formerly called WMV-2), and Zucchini yellows mosaic potyvirus (ZYMV) (Riggs, 2003).

The primary recommendation for managing cucurbit virus diseases has been to plant pumpkins as far as possible from other cucurbit crops to minimize the spread of infected aphids into a pumpkin planting (Brust and Everts, 2010). More recently virus resistance has become available in some cucurbits, most notably squash and introgression of virus host resistance into pumpkin is imminent (Kyle, 1993). Currently Magician is the only commercially recommended cultivar for the mid-Atlantic that has virus resistance. Magician is resistant only to ZYMV. However, it is expected that in the near future many, if not most, pumpkin cultivars that will be commercially available will have virus resistance. Growers are anxious to use this resistance and minimize their losses. Questions about how to manage virus diseases remain one of the most frequent questions on pest management in pumpkin (Everts pers. communication).

Because most cucurbit virus diseases are non-persistent in their aphid vectors, there are limited options for virus management. Insecticide applications have not been effective. Reflective mulches have been used on squash but not pumpkin, which are grown primarily on bare ground. Likewise, frequent applications of mineral oil are expensive, and deemed not reliable enough to justify the expense. Use of border or intercrops also provides a reduction in disease in some, but not all environments. (Damicone, et al. 2007.) It is likely that host plant resistance will become the key tactic in the best management program for virus diseases of pumpkin.

Identification of pumpkin virus diseases by farmers and their advisors 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. In addition different isolates of a virus may result in different symptoms (Davis and Mizuki, 1987). Mixed infections also may yield unusual symptoms, for example a mixed infection of WMV and

ZYMV in Indiana in 2007 resulted in an unusual pitting symptom on fruit (K. Rane personnel communication). Because they cannot be easily identified by symptoms, virus diseases are not easily distinguished by growers.

The four most important virus diseases of cucurbits; CMV, PRSV-W, WMV, and ZYMV, are spread by aphids in a non-persistent manner (i.e., viral particles (virions) are acquired by the aphid on its stylet and are retained in association with the stylet for short periods of time (usually hours). Therefore these viruses are primarily introduced into a crop by aphid transmission from nearby cucurbit crop or from overwintering weed reservoirs. Resistant or tolerant cultivars in Wisconsin also were infected with virus and served as reservoir hosts (Davis et al. 2003). Because several recently released pumpkin cultivars, and pending new releases, have virus resistance or tolerance, new introductions of some virus resistant pumpkin varieties, it would be important to know what cucurbit viruses are prevalent in the mid-Atlantic and which common weed species act as reservoirs for which viruses.

Several surveys on virus prevalence have been conducted in other states, in the past, (Davis and Mizuki, 1987; Sammons et al. 1989). These surveys indicated that the most prevalent cucurbit viruses vary both temporally and geographically. In South Carolina a total of 25 fields were surveyed over a two year period and WMV-2 was the most prevalent virus detected followed by CMV and PRSV-W (Sammons, 1989). In New Jersey, 20 fields sere sampled over a three year period in the mid-1980s. WMV-2 was more prevalent in one year and ZYMV was most prevalent in another year (Roberts, 1987). A small survey in 2005 in New Jersey found WMV-2 was most widespread followed by ZYMV and then PRSV (Wyenandt personal communication). However, a limited survey conducted in Maryland in 1988 found only PRSV and WMV, but not ZYMV present

(Ref.). Extensive surveys conducted in Wisconsin vegetable production areas in 2002 and 2003 found widespread virus incidence (German, 2003) with losses also being reported in Minnesota, Michigan, Ontario, and New York. In Michigan, vine crops were extensively damaged by virus infections in 2003 (Hausback, 2003). Losses were reported in cucumber, summer squash, winter squash, melons, and pumpkins which were diagnosed with single or multiple infections of cucumber mosaic virus, WMV and ZYMV.

Materials and Methods

Foliage tissue in pumpkin fields in Maryland, Delaware, and Pennsylvania (2008 only) and Virginia (2009 only) were sampled for the presence of CMV, PRSV-W, WMV, and ZYMV. Leaves from ten plants in a commercial field were collected. When present, plants with virus disease symptoms such as mosaic, distortion, stunting or mottling were collected. If no symptoms were present, plants were sampled in a random pattern. Weeds were collected in selected fields. Samples were transported to the lab and sent to Agdia, Inc. (Elkart, IN) for Enzyme Linked Immunosorbent Assay (ELISA) testing.

Results and Discussion

In 2008 ZYMV was detected in five pumpkins tissue samples. One sample from Montgomery county MD was positive for PRSV. Only one pumpkin tissue sample tested positive for WMV. However thirty-one symptomatic plants reacted positive to the potyvirus group (PVG) ELISA tests yet did not test positive to PRSV, WMV, or ZYMV. During this same year, a virus survey conducted in thirteen states reported similar anomalous results (Vincelli and Seebold, 2009).

Subsequent analysis indicated that there was a strain of WMV present in Kentucky that did not react to the AgDia Inc. ELISA test for WMV, but was positive to PVG ELISA (Vincelli and Seebold, 2009). It is likely that a number of the samples collected in Maryland, Delaware and Pennsylvania in 2008 were of that strain.

Following the anomalous results of 2008, AgDia Inc developed a new WMV ELISA test that was capable of detecting the (previously undetectable) strain of WMV. In 2009 there was only one pumpkin tissue sample that tested positive to Potyvirus but not to PRSV,WMV, or ZYMV. Twenty-two samples tested positive, or elevated, to both PVG and WMV; one tested positive to PVG, WMV and ZYMV; one tested positive to PVG and PRSV; and one tested positive for PVG, WMV, and PRSV. The most prevalent pumpkin virus in the mid-Atlantic region in 2008 was WMV, followed by PRSV and ZYMV. The most beneficial resistance in pumpkin in 2008 would have been WMV. Magician, which is the only virus resistant pumpkin in the Commercial Vegetable Production Recommendations, has resistance to only ZYMV (Brust and Everts, 2010). We did not detect CMV in any pumpkin in either year.

In 2008 no weed tissue samples tested positive to CMV, WMV, PRSV, or ZYMV. However five did test positive to PVG. In 2009 fewer weed samples were tested and only one tested positive to PVG.

Literature Cited

Brust, J. E., and Everts, K. L. 2010. Commercial Vegetable Production Recommendations. EB 236. University of Maryland in cooperation with Rutgers the State University of New Jersey, Virginia Polytechnic Institute and State University, The Pennsylvania State University, and University of Delaware.

Damicone, J.P., Edelson, J.V., Sherwood, J.L., Myers, L.D., and Motes, J.E. 2007. Effects of border crops and intercrops on control of cucurbit virus diseases. Plant Disease 91:509-516.

Davis, J., F. Beltson, C. Donnelly, and J. Peterson. 2003. Virus resistant plants are not so resistant. Univ. Wisconsin Bulletin No. 112. UWM press.

Davis, R. F., and Mizuki, M. K. 1987. Detection of cucurbit viruses in New Jersey. Plant Disease 71:40-44.

German, F. 2003. Survey for vegetable virus diseases in Wisconsin. Fact sheet 751. UMW press.

Hausbeck, M., K. Saude, and K. Lamour 2003. Detection of virus diseases in cucurbit crops in Michigan. Plant Disease Note 89:1011.

Kyle, M. (ed.), 1993. Resistance of Viral Diseases of Vegetables. Timber Press. Inc., Portland, Oregon.

Riggs, Dale I. M. (editor) 2003. Pumpkin Production Guide. Natural Resource Agriculture and Engineering Service (NRAES-123) Cooperative Extension. Ithaca, New York.

Sammons, B., Barnett, O. W., Davis, R. F., and Mizuki, M. K., 1989. A survey of viruses infecting yellow summer squash in South Carolina. Plant Disease 73:401-404.

Vincelli, P., and Seebold, K. 2009. Report of a Watermelon mosaic potyvirus strain in Kentucky undetected by ELISA. Online. Plant Hearth Progress doi:10.1094/PHP-2009-0313-01-BR.

Zitter, T. A., Hopkins, D. L., and Thomas, C. E. (eds.). 1996. Compendium of Cucurbit Diseases. American Phytopathology Society, APS Press, St. Paul, Minnesota.

Table 1. Summary of virus diseases of pumpkin of importance in the mid-Atlantic region.



Weed hosts (1)

Aphid Vectors

Host resistance available (2)

Cucumber Mosaic (CMV) No (cucurbits) Numerous 60+ spp. S; P in development
Papaya Ringspot (PRSV-W) No Cucurbitaceae(Melothria pendula and Mamordica spp.) 20+ spp. S and P in development
Watermlon Mosaic (WMV, formerly WMV-2) No Trifolium
spp., Malvaceae spp., Chenopodium spp., Amaranthus spp.
20+ spp. S; P in development
Zucchini Yellow Mosaic (ZYMV) Possible Not known Several? S; P in development

(1) Zitter et al. 1006. Compendium of cucurbit diseases.
(2) Pumpkin=P; Squash=S

Table 2. Results of virus disease assay in 2008.

Host Plant Location (County) Positive Results
Eastern Shore, MD
Pumpkin Wicomico Potyvirus (4)
Pumpkin Queen Anne's Potyvirus (4)
Pumpkin Caroline Potyvirus
Southern MD
Pumpkin St. Mary's Potyvirus (2)
Pumpkin Charles Potyvirus and ZYMV
Pumpkin Prince George's Potyvirus (2)
Central MD
Pumpkin Howard Potyvirus, ZYMV and WMV
Pumpkin Carroll Potyvirus
Pumpkin Montgomery Potyvirus; Potyvirus and PRSV
Spurred Anoda Montgomery Potyvirus
Western MD
Pumpkin Allegany Potyvirus
Pumpkin Garrett Potyvirus and ZYMV
Pumpkin Washington Potyvirus (2); Potyvirus, ZYMV, WMV
Pumpkin Washington Potyvirus 
Pumpkin Frederick  Potyvirus
Pumpkin Sussex Potyvirus; Potyvirus and ZYMV
Pumpkin  New Castle  Potyvirus 
Pokeweed Sussex  Potyvirus 
Pumpkin New Castle  Potyvirus 
Pokeweed Lancaster Potyvirus
Burr Cucumber Lancaster Potyvirus
Ground Cherry Lancaster Potyvirus
Pumpkin Lancaster Potyvirus (4)

Table 3. Results of virus disease assay in 2009.

Host Plant Location (County) Positive Results
Eastern Shore, MD
Pumpkin Queen Anne's Potyvirus (1); Potyvirus and WMV (1); Potyvirus and elevated WMV (4)
Pumpkin Caroline Potyvirus and WMV (2)
Pumpkin Dorchester Potyvirus and WMV (1); PRSV and Potyvirus and WMV (1); None (6)
Horsenettle Dorchester None
Central MD
  Howard Potyvirus and WMV (1); Potyvirus and elevated WMV and ZYMV (1)
Southern MD
Pumpkin Charles Potyvirus and WMV (1)
Pumpkin Calvert Potyvirus and WMV (2)
Western MD
Pumpkin Frederick  Potyvirus and WMV (2)
Pumpkin Westmoreland Potyvirus and WMV (3)
Pumpkin Sussex PRSV and Potyvirus; Potyvirus and WMV (2); Potyvirus and PRSV and WMV (1)
Horsenettle Sussex None (3)
Spurred Anoda Sussex Potyvirus (1)
Morning Glory Sussex None (1)
Pumpkin Kent Potyvirus and WMV (1)
Pumpkin New Castle Potyvirus and WMV (1)

Kathryne Everts
University of Maryland
Department of Plant Science and Landscape Architecture
Salisbury, MD 21801
410-742-8788 (phone)
410-742-1922 (fax)

Plant Pathology

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