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"Stopping the Spread of INSV to Other Plants" Q. A timely question/answer article last week on your Web site!! Could you please go further on how to prevent INSV from spreading further in my own garden? Once I get rid of the plants, what can I use in the rest of the garden? Would the virus affect the natural mountain laurels that are behind the impatiens in addition to the other evergreens? You said the virus is in the seed. I planted my impatiens as a continuous border in the back, the only break was a narrow stone path. The impatiens on the right side of the path seem to be fine, but on the left side they had the problem. I thought it was an overwatering problem by the sprinkler system. Thanks. A. No, it's not a problem with your sprinkler system. This virus called impatiens necrotic spot virus, or INSV for short, came in on the impatiens plants you bought. When you bought the plants more than likely they showed no symptoms of the virus. It's not until much later on do you start to see the symptoms of this awful disease. As with human viruses, there is no cure for plant viruses like INSV. As I mentioned in last week's column, it is a serious problem facing the plant industry. Some of the very largest commercial growers in the country are doing what's called "virus indexing" to help clean up their stock plants that are used for starting cuttings of new plants. That helps stop the spread of the virus somewhat throughout the plant industry but more of that needs to be done. I'm aware of one large national commercial grower that has a virus indexing program for their New Guinea impatiens, an important flower crop financially, but I'm not aware of any work being done to regular old impatiens. I hope someone is or will be working on it. Since there is no cure for INSV, the only thing you can do is to try to stop the spread of this virus to other plants in your garden. Pull up and discard all of the sick impatiens plants and any other plants affected by INSV. Once in your garden, INSV is spread from infected plants to healthy plants by thrip, a tiny, nearly-invisible insect. Along with removing and discarding all infected plants you should also treat your other plants for thrip to stop the spread of the virus to other plants in your garden. I use Neem Oil to control thrips. Made from the seeds of the Neem tree that grows in India, this amazing all-natural spray is an insecticide, fungicide, and miticide all in one. It can be used on all plants including roses, perennials, annuals, trees, shrubs, flowers, fruits, vegetables, and house plants. It controls all stages of insects (adult, larvae, and egg). It acts as a growth regulator, antifeedant, repellent, and contact killer of many common and hard-to-control insect pests, including thrip. Although the list of plants affected by INSV keeps growing, I do not know if it affects mountain laurel and evergreens since most of the research done thus far has focused on flower crops, vegetables, and weeds. Click here to read more about Neem Oil and order it from Pernell Gerver's Online Store.
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