Cucurbit Genetics Cooperative Report 7:78-79 (article 34) 1984

Epidemics of Zucchini Yellow Mosaic Virus and Other Cucurbit Viruses in Egypt in the Spring of 1983

R. Provvidenti

New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456

H.M. Munger

Cornell University, Ithaca, NY 14853

H.O. Paulus

University of California, Riverside, CA 92521

In Egypt, during the spring of 1983, viral diseases were responsible for devastating epidemics in cucumber, melon, squash and watermelon fields. Our surveys, which were conducted in May, included experimental and commercial fields in the Delta, along the Nile River, from Cairo to Sids, Ismailia (Suez Canal) and an agricultural development project in the Sinai.

Particularly affected were cultivars of summer squash (Cucurbita pepo L.), which reacted to viral infection with plant stunting, severe foliar symptoms and distorted fruits. These malformed fruits were frequently sold in local markets. In fields where viral infection had occurred in an early stage of plant growth, production was totally lost, since fruits either aborted or remained very small.

Because of the similarity in symptomatology, it was often difficult to differentiate plants infected with watermelon mosaic virus 1 (WMV-1) from those infected with zucchini yellow mosaic virus (ZYMV). Both of these viruses caused very severe foliage mosaic and knobbed fruits, and they appear to be the most prevalent and widespread. WMV-1 and ZYMV were followed in order of importance, by cucumber mosaic virus (CMV) and watermelon mosaic virus 2 (WMV-2). Squash mosaic virus (SqMV) was confined to isolated melon and squash plants, and its spread was impaired by low beetle populations. Conversely, CMV, WMV-1, WMV-2 and ZYMV were spread efficiently by several aphid species.

The presence of ZYMV in Egypt and of the other viruses was confirmed by the analysis of infected specimens. The identification was accomplished using electron microscopy, serology and diagnostic hosts. The Egyptian isolates of ZYMV incited symptoms closely resembling those caused by European isolates of this virus (1,3) and the American strain, ZYMV-CT (5).

In Egypt, a good control of these viral diseases was achieved when plants were grown initially under low plastic tunnels. When the plastic was removed to facilitate pollination, plants appeared to be healthy and produced a good crop. However, without the protective plastic shield, which had interfered with the activity of the vectors, these plants eventually succumbed to viral infections.

Plastic tunneling obviously adds to the production cost, but it offers an alternative to the total loss of the crop, particularly in years of devastating epidemics.

In addition to Egypt, ZYMV has been found in France, Germany, Israel, Italy, Morocco, Spain (2) and the USA (4,5).

Literature Cited

1. Lecoq, H., M. Pitrat, and M. Clement. 1981. Identification et caracterisation d'un potyvirus provoquant la maladie du rabougrissement jaune du melon. Agronomie 1:827-834.
2. Lecoq, H., V. Lisa, and G. Dellavalle. 1983. Serological identity of muskmelon yellow stunt and zucchini yellow mosaic virus. Plant Dis. Rept. 67:824-825.
3. Lisa, V., G. Boccardo, G. D'Agostino, G. Dellavalle, and D'Aquino. 1981. Characterization of a potyvirus that causes zucchini yellow mosaic. Phytopathology 71:667-672.
4. Provvidenti, R., D. Gonsalves, and H.S. Humaydan. 1983. Occurrence of zucchini yellow mosaic virus in the United States. Cucurbit Genetics Coop Rept. 6:99.
5. Provvidenti, R., D. Gonsalves, and H.S. Humaydan. 1984. Further occurrence of zucchini yellow mosaic virus in the United States. Cucurbit Genetics Coop. Rept. 7:80.