A mosaic virus is a type of plant virus that is transmitted by certain insects. Generally, a mosaic virus will affect any kind of cultivated vine crop including cucumbers, squash, melons, pumpkins, and gourds. Plants that are infected by this type of virus are generally lost. True to its name, plants that have been affected by a mosaic virus often have mottled leaves and speckled fruit.
When a younger plant contracts a mosaic virus, the results are usually severe. As a plant matures, this type of virus will stick with the plant causing damaged fruit, lack of fruit, or plant death. When these viruses occur on a large scale, entire fields of crops may be affected, since these viruses are easily spread from one plant to the next. In short, a commercial farm that has been attacked by a mosaic virus can suffer a massive economic impact.
While there are a few different types of mosaic viruses, five common types exist. Cucumber, squash, watermelon, zucchini, and papaya mosaic viruses are abundant throughout the world. The main issue that most farmers have is identifying what type of mosaic virus they are faced with. If a plant appears to have speckled leaves, it is best to send that plant to a laboratory for identification purposes.
Unfortunately, insects spread this type of virus from plant to plant with ease. Insects pick up viruses by simply penetrating an infected plant. Once an insect has been infected, the virus is spread whenever an infected insect visits another plant. The best way to avoid plants from contracting a virus is to choose virus resistant plants. If this it not a possibility, there are other options.
Controlling the number of weeds that are allowed to grow near plants is a good idea. Since insects originally contract a virus from weeds, keeping these weeds away from plants is logical. Contrary to popular belief, attempting to eliminate insects from a garden space is not effective.
Since an insect only needs to probe a plant in order to infect that plant, killing an insect won't prevent a virus from spreading. The only way to control insects is to use an insect repellent on a daily basis — even then, you would have to kill the insect before it lands on any plants. While farmers of all kinds dread plant viruses, there really isn't a good way to prevent this from occurring.