I also had a much appreciated hibiscus of 19 years. It had three large trunk divisions. Last week the largest just fell over. Inside I found a large white worm like thing. Today I was checked the rest of the bush and found it to be unhealthy. While digging it out to replant a new hibiscus, I have found at least a dozen 1" borers (?). What can I do to keep the area safe for a new hibiscus? What are these borers?

Were the two larvae (the one in the stem) and the doze or so similar in appearance? It's unusual that there would be that many - and by your description, I'm assuming they were in the soil. They may or may not be related to the problem. Hibiscus, as with all flowering shrubs, need to be pruned on a regular basis to maintain healthy wood. If left unpruned, the wood becomes thick, old, and very susceptible to diseases, borers etc. I'm also going to assume that you removed the larvae that you found in the hold before you replanted the new hibiscus. Your approach at this point is to keep the new plant healthy - fertilize for vigor, water during periods of drought, and prune yearly to maintain healthy wood.

Thank you for your response. There was one large one higher up in the stem and the many others were a little over an inch long and lower in a separate stem. I found none in the soil. The plant was damaged by the strong wind storms that hit our area a few Julys ago. I did the best i could to remove as much of the trunk as possible and applied Milky Spore to the area. Funny thing though, I put a little Milky Spore Powder in a Dixie cup with borers 2 days ago and they are not dead yet. Thanks again.