Your questions, the garden guy's answers: Of bees, bonsai and more

Gardeners asked about huge bees and other summer concerns. Some of their questions, raised in recent phone calls to the Extension Office, related to the dry weather.

Q. We have really huge bees, 2 to 3 inches long, burrowing big holes in our front yard. I looked them up online, and I think they could be Japanese hornets. We have killed four of them now, and I see a fifth one out there. We want to rid ourselves of these bees, so our young children and pets are safe to go in the yard. J.L., Lynchburg

A. Your front yard has become home to one of the larger members of the bee family, known as cicada killer. These robust wasps fly into the tree tops, catch a cicada and bring it back to their nest in the ground to feed their young. Females are able to sting, but they show little or no interest in people. My advice: Leave them alone and let the cool autumn weather put an end to their activity. Cicada killers prefer to nest in places with scant vegetation, so you could possibly prevent their return next year by planting grass, flowers or shrubbery.

Q. I have a bonsai, and need to know how to water it and trim it. It is an azalea. A.H., Hurt

A. Potted bonsai plants need daily watering in summer and less water at other times. Bonsai are grown in a variety of shapes and styles, and pruning is done accordingly.

Q. One quick question: My wife grows marigolds in potting soil in window boxes. In one of the two boxes, the marigolds turned white, wilted and then turned brown. They die in one window box and, in the other one, they are perfectly healthy. The soil is the same in both boxes, and we use new soil every year. There are two kinds of marigolds. What is wrong? C.P., Lynchburg

A. Marigolds, the flowers often planted to repel insects, are not bullet-proof. White leaves indicate a spider mite infestation, and you can see the mites for yourself under a
magnifying glass. When marigolds wilt and die, even when you keep them watered, the cause is likely to be fusarium wilt. Although using new soil in the window boxes every year is a recommended practice, the fusarium wilt fungus can live from year to year in dirt found on the surface of the used window box. Next spring, you can either buy new window boxes or clean the old ones by soaking them in a 10-percent solution of household bleach for 30 minutes. Rinse before use.

Q. I am calling you to ask is there a blight on pin oak trees in the Lynchburg area. I seem to have lost one of my pin oaks in the last three weeks or a month. J.T., Lynchburg

A. The dry conditions are very hard on pin oaks. These swamp-loving trees get a disease called pin oak blight (aka endothia canker), which causes cankers on their trunks and branches. The dead branches are often seen in dry weather. Several others have called me about dying pin oak trees in recent days.