Aphids, for example, can carry cucumber mosaic virus from ragweed or milkweed to cucumbers, or raspberry mosaic virus from wild raspberries to cultivated raspberries. Rip out any cultivated plant known to be infected with a virus. Viruses even solicit rides from humans. Tobacco mosaic virus infects a wide variety of plants, and can be carried on smokers' fingers. Plant choice can help avoid virus problems.
Some varieties are virus-resistant.
Don't blame all your plant problems on viruses. Definitive diagnosis is often difficult without a laboratory test. Perhaps you're just overwatering. This article first appeared January 13, 2001. We welcome your feedback.