Aphids and Cucumber Mosaic Virus

Many vegetable growers have had some experience with cucumber mosaic virus and I often get questions about how to prevent it. Unfortunately, this is a very difficult disease to manage.

Hundreds of plant species can host this virus. It is spread from plant to plant by aphids. Therefore there can be a reservoir of the virus in vegetation around the field or it may be spread from neighbouring crops. The list of host crops includes peppers, vine crops, alfalfa, clovers, and tomato. Common host weeds are pigweed, lamb's-quarters, chickweed, milkweed, and dandelion.

To transmit the virus, an aphid simply has to probe an infected plant, followed by an uninfected plant. Over 80 species of aphids can transmit the virus. These aphids may be moving across the landscape, tasting plants while looking for their preferred crop. They may not colonize your crop, so you may never see them. It means that spraying for aphids is not effective at all in preventing cucumber mosaic virus. An infected aphid could move through at any time, and its first contact with the insecticide may be when it lands for a test probe on your plant. With this one probe, it has already transmitted the virus. In a severe soybean aphid year, cucumber mosaic virus may be more widespread due to the large numbers of aphids moving through the area looking for soybeans.

The severity of the virus outbreak will depend on the strain of the virus, the crop cultivar, and the timing of the infection.

Options for controlling the disease are few, and often of limited effectiveness. Control weeds in and around the field, remove any plants showing virus symptoms, and if possible, choose cultivars with some resistance to the virus.

Looking forward to spring, this has been Janice LeBoeuf, Vegetable Crop Specialist in Ridgetown, reporting for the Ontario Ministry of Agriculture, Food, and Rural Affairs.

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