My 4+ years old American Wisteria is experiencing the same symptoms as "beeccasap". It is only August and the Wisteria has started losing leaves, which turn yellow and then fall down. Many branches are dead now. I tried adding 10-1-10 fertilizer when someone at the Botanical Gardens told me that it may be due to lack of nitrogen. However, that has not helped.
Other plants are still unaffected, such as the Carolina Jessamine, which is also trained on the same pergola (different corner) as the Wisteria. Any advice?