Nasty Tospovirus Killing AVs
Two long-time hobby AV growers/hybridzers and one grower new to AVs have recently lost their entire collections because of INSV - impatiens necrotic spot virus. This virus infects over 600 plant species, including African violets and other gesneriads. These growers live across the US in varying places: west coast, east coast, Michigan.
There isn't a lot of research regarding AVs and INSV. Please follow the link below for pictures of how it devastated one grower's collection.
For more information about INSV, an article will be coming out in the next AVSA magazine written by the grower whose pictures are shown.
Regarding diagnosis: http://www.onhort.com/Improving-INSV-diagnosis-article2586
General information: http://www.utextension.utk.edu/publications/spfiles/sp370a.pdf
This is what seems most important to know:
1. The virus can be "silent" in some plants, yet can be spread to other plants through thrips or propagation.
2. The virus is only spread by one insect: thrips. It is possible, but not likely because of how the virus works, to spread it to another plant through infected tools (get sap of infected plant in cutting blade and use it on another plant). If you have one silent infected plant and you get thrips, they can infect every plant you have.
3. The virus is systemic; it lives in varying concentrations in all parts of infected plants, whether there are symptoms or not. If you plant a leaf from the infected plant, all resulting plantets will have it. If you crown the plant, the new plant will have it. If you take off suckers, the resulting plantlets will all have it.
4. Monitoring for thrips with blue sticky cards is essential. As soon as you see a thrip, take fast action. Please follow the guidelines in the article above.
5. Testing is not 100% sure. There needs to be enough virus in the part you test, so a plant with a low level could be positive and test negative.
6. No one knows how long it takes symptoms to show in AVs, so isolation may not be effective (some plants display symptoms in days, others in months). Also, if you have some silent carriers, you might think they were fine.
7. Tests are available at about $5 a test. For a large collection, it would simply be less expensive to buy new plants than to test them all. Also, since the plants might test negative when they were positive, some growers feel that throwing out everything is the best thing to do.
Here is a link that might be useful: CLICK here for pictures of INVS on AVs