Pest Of The Month: Cucumber Mosaic Virus

Cucumber Mosaic Virus

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Identification

The first symptom of CMV is often a clearing of veins, followed by development of mottling consisting of irregularly shaped, dark-green areas alternating with light-green or yellow areas. On many species, CMV shows symptoms on leaves known as “shoestringing,” which causes young leaves to appear narrow and the entire plant to be stunted.

On tomatoes, symptoms can include a “shoestring” appearance of the leaves. The internodes of the stems are shortened, and the plants appear bushy and markedly stunted. Leaves are extremely deformed and have a green mosaic pattern. Infected fruit exhibit white-to-yellow rings, areas, or v-shaped line patterns and can resemble tomato spotted wilt virus.
CMV causes cucumbers to display a pronounced mottling and fruits are wrinkled and misshapen. Growth of these plants is usually stunted and produces few flowers. Fruits often are wrinkled and misshapen and may appear gray. Infected fruits may be bitter.

CMV in peppers causes slightly different symptoms. Pepper plants often have severe foliar damage, shown as mosaic and necrotic rings. The pods often are misshapen and display chlorotic rings and spots.

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Survival And Spread

CMV has one of the widest host range of any known plant virus. It can infect a great variety of other plants, including squash, melons, peppers, beans, tomatoes, carrots, celery, lettuce, spinach, beets, various weeds, and many ornamentals and bedding plants.

CMV can be transmitted from plant to plant both mechanically by sap and by more than 60 different aphid species aphids in a non-persistent manner. The virus often appears following cool conditions that favor aphid flights. CMV is not seedborne in tomato and does not persist in plant debris in the soil or on workers’ hands or clothing. Dayflower (Commelina sp.) is a major host for cucumber mosaic virus.

Management Methods

The occurrence of this virus is erratic and unpredictable; consequently, control of this disease can be difficult. There often is a loss of 10% to 20% of yield and even if harvested, crops are commonly found in poor condition.
The use of resistant varieties is an important tool for growers when available. Commercial varieties of peppers, cucumber, and squash with resistance are available.

In studies, silver reflective plastic mulches have been shown to be effective in repelling aphids, reducing or delaying virus infection.
Removing weeds and diseased plants from fields also can help reduce the chance of infections.

Use of insecticides to control the aphids often is not effective in controlling CMV because of the short acquisition and inoculation time and the fact that insecticides may cause aphids to become irritated and move from plant to plant increasing in field transmission.
Crop oils and insecticides, which inhibit feeding activity, may interfere with virus transmission.

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