Beehive In Junipers & Japanese Maple Stems Turning Black

Question:

 I had a beehive in my junipers last year. I guess it got too cold for them because I don’t see any activity. Is there something I can spray on junipers to make sure they don't come back?  

Answer:

  •  More than likely this was a Yellow Jacket nest and not a beehive.
  • In late November, a Yellow Jacket nest becomes inactive as the worker and male Yellow Jackets die. The Queens abandons the old hives and hibernates elsewhere over the winter. In the spring, she emerges from her hibernation to seek and establish a new colony in a different location and never in an old hive. This hive remains active until November when the process begins or ends again.
  • Hornets, Honey, and Bumble Beehives are inactive during cool, wet weather but you’ll notice activity in March with the longer and warmer days.
  • With Yellow Jackets, your best defense is to set out your Yellow Jacket traps in the spring, March/April and trap the Queen(s) while she is searching for a new home.
    • The traps from the previous year should be washed out with warm soapy water, and new attractant should be installed. The attractant should also be refreshed in August for the fall season. 

Question:

We have a six-year-old Coral Bark Japanese Maple. Last year, a few of the smaller branches turned black, and we pruned them off.  Now one of the three main branches is doing the same thing, and the leaves are withering. The shape of the plant will be ruined if we remove it.  What should we be doing?

Answer:

  • It’s never good news when the stems of a Japanese Maple turn black.
  • The black coloration is a primary indicator of a vascular disease called Verticillium Wilt. Verticillium Wilt is a soil-borne fungus disease that’s common in our Bay Area soils. When the infected stems are cut, you’ll find black streaking through the tissue.
    • It attacks a wide range of ornamental and herbaceous plants including, tomatoes, peppers, roses, Pistache and Camphor trees.
    • The fungus works its way up the plant from the roots disrupting the vascular tissue that is responsible for transporting water and nutrients throughout the plant. Unfortunately, we have no controls for this problem.
    • The disease does attack without warning. Our poorly draining, heavy clay soil and excessive summer watering doesn’t help. It’s particularly frustrating when Verticillium Wilt attacks established and thriving ornamentals. With tomatoes and other vegetables, we can plant resistant varieties, but that’s not the case with Japanese Maples.
  •  I’d removed the infected limb because it is not going to recover and encourage the new growth by feeding it an organic fertilizer.  A replacement branch can be selected from the new growth.
  • Leaf blight can also cause dark, deadened shoots and curled, darkened leaves on the tree. Airborne bacteria, such as Pseudomona is also responsible for leaf and branch dieback on a Japanese maple. But Verticillium Wilt is by far the primary suspect.