Plant virus can not be diagnosed from appearance alone. One uses appearance to make a guess, but the only way to diagnose with certainty is to perform a immunoassay test. There are test kits available, I am not current on prices.
This company provides both test kits for specific viruses and has a testing lab where you can send them samples. We used them when we owned a farm. Not for bonsai specifically. This company makes test kits for blueberry viruses, orchid viruses and viruses for a wide array of agricultural crops. They also make test kits to detect GMO plants. Want to know if your corn, apples or rutabagas are GMO, their test kits tests for the signature transgenic virus particles used to move around DNA.
Agdia, Inc. is the leading provider of test kits for plant pathogens and transgenic (GMO) traits. Agdia diagnostics are used all over the world for laboratory and field based detection of plant viruses, bacteria, and fungi that cause plant disease.
www.agdia.com
Every County in the USA has a USDA Farm Extension Office. The Extension service is usually administered by your local Land Grant University. For example Michigan State University is the Land Grant University for Michigan. University of Illinois at Champaign-Urbana is the Land Grant University for Illinois. Each county will have an Extension Agent who specializes in plant diseases. You might put a call into your local extension office and see what they say about diagnosing your problem or whether they have a local lab that can diagnose the problem for you.
This all said, IF THE WISTERIA CUTTINGS WERE INEXPENSIVE. Myself I would destroy the cuttings, burn or put in municipal waste. DO NOT COMPOST the infected plants. Throw out into municipal waste, or burn the soil they were in. Sterilize the pots they were in before reusing the pots. Wash your hands after touching the infected plants before handling any of your other houseplants, bonsai, garden plants or vegetables. The cost of testing for virus is probably more than the cost of your cuttings. It would be better to destroy the cuttings and start over with plants purchased from nursery that is USDA Inspected.
Mosaic virus are highly contagious. They are spread by cuttings tools, human hands transferring virus particles from infected plant to other plants. They can also be spread by insects that feed on the infected plants. Aphids are notorious for spreading virus.
Spend a little more. Only buy wisteria from a real brick and mortar nursery that maintains a USDA Certification. Ask the nursery about whether they virus test their propagation stock. If they do not, move on to a nursery that does. Many nurseries will buy only from wholesalers who maintain good disease control. For example Isle Nursery routinely tests their propagation stock for virus. Many retail nurseries buy from Isle because they know they will be getting clean, virus free plants.
So that is my suggestion. Burn your wisteria, start over. You don't have many years invested. It is cheaper to start over than to have these diseased plants spread the virus to other trees, houseplants and vegetables in your collection.
