Mosaic Virus Diseases of Cucumber
» Cucumber mosaic, papaya ringspot, watermelon mosaic, and zucchini yellow mosaic are important viral diseases of cucumbers.
» Symptoms of these mosaic diseases are similar and difficult to distinguish from each other.
» Host resistance and preventing the spread of viruses is the key to managing these diseases.
The disease, cucumber mosaic, is caused by the Cucumber
mosaic virus (CMV). CMV is one of the most common and
destructive cucurbit viruses, and it is widely distributed
throughout temperate and tropical areas of the world.1,2
CMV can infect over 1200 plant species including both
monocots and dicots.3 There are many strains of CMV that
differ in the symptoms they cause, the range of hosts they
infect, and their means of dispersal.4 Yield losses of 10 to
20% are common, and losses of up to 100% can occur.3
Cucumber plants can be infected with CMV at any stage, and
once a plant is infected the virus spreads systemically within
the plant. Symptoms appear 7 to 14 days after infection and
develop most quickly at temperatures of 79 to 89 °F.1,3,4 A
light- to dark-green mosaic or mottling appears first on the
youngest leaves (Figure 1). New leaves are stunted and
distorted with the outer edges curling downward.3,4 Plants
are stunted, sometimes severely, with shortened internodes
resulting in a bushy canopy. Flowers can show abnormal
features such as green petals. Fruit produced on infected
plants are often smaller and somewhat deformed, and show
mosaic patterns of light and dark green on the skin.
Many crop-, ornamental-, and weed-species can serve as
reservoir hosts of CMV. Some common weed hosts include
bur-cucumber, burdock, common milkweed, horsenettle,
jimsonweed, marsh yellowcress, nightshades, pigweed,
pokeweeds, white cockle, and wild-cucumber. Perennial
hosts, such as alfalfa, are important reservoir hosts of CMV
in regions with cold winters.1,3,4
The severity of CMV epidemics depends on the number of
aphids present and the number of infected reservoir hosts.
Aphid numbers tend to be higher when conditions are warm
and dry.3 Cucumber beetles can also transmit CMV, but not
as effectively as do aphids.4
WATERMELON MOSAIC / PAPAYA RINGSPOT
Once thought to be different strains of the same virus,
Papaya ringspot virus – watermelon strain (PRSV-W) and
Watermelon mosaic virus (WMV) are now recognized as distinct
viruses. WMV has a host range that includes most cucurbits,
many legume species, and other plants such as carrot and
spinach. WMV is found worldwide in most cucurbit growing
regions. In the U.S., watermelon mosaic occurs most
commonly in the southern and western growing regions, as
well as in New Jersey and New York.1 Yield losses above 50%
from WMV infection are not uncommon. The host range of
PRSV is mostly limited to cucurbits, but it also infects species
of Chenopodium, and PRSV-W is most commonly found in
tropical and subtropical regions.
The symptoms resulting from WMV and PRSV infection are
similar. All plant parts can be affected, with the severity of
symptoms depending on the age of the plant at the time of
infection. Earlier infection results in more severe symptoms.
A green- to dark-green mosaic with vein banding occurs on
cucumber leaves, and leaves may show narrow, elongated
growth if infected when young.1 The fruit of WMV infected
plants are typically stunted, gnarled, and sometimes knobby.
Symptoms of watermelon mosaic usually develop within 7 to
14 days after infection, and mixed infections of WMV and
CMV are common, especially later in the season.
WMV can overwinter on annual and perennial legumes such
as clover, while PRSV-W usually spreads from wild perennial
ZUCCHINI YELLOW MOSAIC
The Zucchini yellow mosaic virus (ZYMV) can be found
worldwide in cucurbit growing regions, and zucchini yellow
mosaic has become an economically important disease in
several areas. ZYMV mostly infects cucurbits. Non-cucurbit
hosts have been reported, but these are probably not very
important in spreading the disease to cucumbers.1,2
Initial symptoms of zucchini yellow mosaic develop within 7
to 14 day of infection. Symptoms include prominent yellow
mosaic symptoms on leaves, leaf distortion, and stunted
plants. Fruit produced on infected plants may be small,
mottled, and malformed (Figure 2).2
MANAGEMENT OF MOSAIC VIRUS DISEASES
Resistance to CMV is available in many cucumber cultivars,
conferred by the combination of three resistance genes.1,3
Varieties with the wmv(02245) gene have resistance to
watermelon mosaic, and there are at least three sources of
resistance to PRSV-W.5,6,7 Resistance to ZYMV is available in
some varieties.8 Growers should check the disease
resistance profiles of varieties when selecting seed and
compare with the diseases that occur in their area.
All four of these viruses are transmitted by several species of
aphids in a non-persistent manner. With non-persistent
transmission, the aphid vector picks up the virus after
feeding on an infected plant for a few seconds to minutes.
The aphid can then transmit the virus to a healthy plant very
quickly, but the aphid only retains the virus for a short time,
often for only a few hours or until the aphid starts feeding.
To lower the rate of infection by these four viruses,
cucumber crops should not be planted near or downwind of
established plantings of hosts that may be infected with any
of the viruses. Planting early in the spring can allow the crop
to become established before aphids arrive to spread the
viruses, and the use of reflective mulches and/or row covers
can help keep aphids away from plants early in the season.
Reflective mulches repel aphids, but lose effectiveness as
the canopy covers the mulch. Row covers act as a physical
barrier to aphids, but they must be removed when plants
start to flower to allow pollinators access to the flowers.1,3
Weed management of reservoir hosts in and around fields
and greenhouses can help lower the rate of virus spread,
but it can be difficult, especially for effective management of
CMV, because of its very wide host range.1,3 Weed control
early in the season has the most impact. Weeds should be
cleared from an area of at least 10 feet around
greenhouses, and elimination of reservoir hosts to at least
100 yards around production fields is recommended to
effectively reduce virus spread.4
Managing aphids with insecticides is generally not effective
for reducing the spread of non-persistently transmitted
viruses because the viruses are introduced into the plants
before there is time for the insecticide to kill the aphid.3
The application of mineral oils can help slow the spread of the
viruses because the oil interferes with the release of the
virus from the aphid’s stylet.4
If feasible, roguing virus-infected plants early in the season
can help reduce the spread of viruses within a planting. Also,
planting a non-host trap crop, such as wheat, around a
cucumber field can help to “clean” the aphids of viruses as
they feed on the trap crop before moving to the
cucumbers.4 Prompt destruction of crop debris after the
final harvest can help prevent the spread of these viral
diseases to other nearby plantings.1
1 Keinath, A., Wintermantel, W., and Zitter, T. 2017. Compendium of cucurbit diseases and pests. American Phytopathological Society. St. Paul, MN.
2 Zitter, T. A. and Banik, M. T. 1984. Virus diseases of cucurbits. Vegetable MD Online. Cornell University. Fact Sheet Page: 732.40.
3 Zitter, T. and Murphy, J. 2009. Cucumber mosaic. The Plant Health Instructor. DOI: 10.1094/PHI-I-2009-0518-01.
4 Babadoost. M. 1999. Mosaic diseases of cucurbits. Report on Plant Disease. University of Illinois Extension. RPD No. 926.
5 Tian, G., Miao, H., Yang, Y., Zhou, J., Lu, H., Wang, Y., Xie, B., Zhang, S., Gu, X. 2016. Genetic analysis and fine mapping of watermelon mosaic virus resistance gene in cucumber. Molecular Breeding Vol36 issue 9 article 131. DOI 10.1007/s11032-016-0524-5.
6 Grumet, R., Kabelka, E., McQueen, S., Wai, T., and Humphrey, R. 2000. Characterization of sources of resistance to the watermelon strain of papaya ringspot virus in cucumber: allelism and co-segregation with other potyvirus resistances. Theoretical and Applied Genetics (2000) 101: 463. DOI:10.1007/s001220051504.
7 Wai, T. and Grumet, R. 1995. Inheritance of resistance to the watermelon strain of papaya ringspot virus in the cucumber line TMG-1. HORTSCIENCE 30(2):338–340.
8 Svoboda, J., Leisova-Svobodova, L., and Amano, M. 2013. Evaluation of selected cucurbitaceous vegetables for resistance to Zucchini yellow mosaic virus. Plant Dis. 97:1316-1321.
For additional agronomic information, please contact your local seed representative. Developed in partnership with Technology Development & Agronomy by Monsanto.
Performance may vary from location to location and from year to year as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. The recommendations in this article are based upon information obtained from the cited sources and should be used as a quick reference for information about cucumber diseases. The content of this article should not be substituted for the professional opinion of a producer, grower, agronomist, pathologist and similar professional dealing with this specific crop. SEMINIS DOES NOT WARRANT THE ACCURACY OF ANY INFORMATION OR TECHNICAL ADVICE PROVIDED HEREIN AND DISCLAIMS ALL LIABILITY FOR ANY CLAIM INVOLVING SUCH INFORMATION OR ADVICE. 180118130224 042018DME
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