Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SUNDAY, April 18, 1993 TAG: 9304190267
SECTION: HOMES PAGE: B-6 EDITION: METRO
SOURCE: John Arbogast
DATELINE: LENGTH: Long
BORER HAS A DAMAGING EFFECT ON RHODODENDRONS
Q: When there is a nice prolific rhododendron in my yard, I find a stem or branch that has died. When I prune the stem, I find a hole in the center that extends from the tip of the branch all the way to the root. If I am correct, there is a spray that will help this problem, but I am not sure what, nor do I know when the right application time is. Perhaps you have answers. F.H.M., BedfordA: According to Eric Day, manager of the Virginia Tech insect identification lab, what you described sounds like the azalea stem borer. Even though you noted that the hole extends from tip to roots, Day said the a problem is mainly on new growth.
Here are the controls he recommends:
Cultural: It is very important to prune affected branches down to good portions just as soon as wilting is noticed. Also, promote vigorous growth through proper fertilization, adjustment of pH if necessary and provide water during dry times.
Use insecticides: either lindane or Dursban to treat 1-year-old stems throughout the rhododendron in mid-May and mid-June.
Q: Several years ago I bought a load of topsoil and some framing lumber and built a terraced garden. The first couple of years my garden did great. I had tomatoes, peppers, squash and zucchini. About three years ago, I started planting tulip bulbs in my garden, and now it's just about covered in all types of tulips. After the tulips bloom, I plant my tomatoes and peppers between the rows of tulips, but the vegetables won't grow. Is there any reason that tulips and vegetables can't grow in the same space? K.P., Salem
A: I talked with Diane Relf, extension specialist in consumer horticulture at Virginia Tech, about your situation. She said that she has not heard of any antagonistic problem between tulips and vegetables.
According to Relf, here are possible causes for your problem:
Competition between the plants for nutrients.
Differences in the cultural requirements between vegetables and tulips.
The fact that watering and weeding needed for a productive vegetable garden may be bad for tulips. Her point here is that the gardener can't neglect one in favor of the other plant.
Shade or other site-related factors that may have changed over the years. Review these items and decide what if anything can be changed before planting vegetables this spring.
Q: I usually plant at least 32 to 40 tomato plants each year, which is certainly more than enough, but I love to raise them and to give them away. I raise several old-time tomatoes that are not disease resistant, so I must spray with Manzate. I am unable to rotate my rather small garden in such a way that some tomatoes overlap. Is there anything that I can do to take the place of rotation? I put everything I can back on my garden each year, plus rotten sawdust and horse manure. My soil tests extremely high on all accounts. B.J., Narrows
A: Unfortunately, there is no answer to your situation where crop rotation can't be practiced and you are not growing disease-resistant varieties. Be prepared for problems on occasion.
You are doing the right things in adding a lot of organic matter to the soil each year and taking soil tests and following recommendations to maintain the proper pH for vigorous vegetable growth.
Two additional practices you should follow are: 1.) follow good sanitation, which means remove and destroy all plant parts, including fruits, that might be showing symptoms of disease just as soon as symptoms are first observed, plus remove stakes, cages and other plant structures promptly at the end of the growing season; and 2.) till in the fall so that disease organisms, insects and perennial weeds may be reduced by killing or inactivating them through burial or exposure to harsh winter weather.
Q: I have had a good white grapevine for a few years. The grapes that I have gotten have been delicious, but there have been so many black ones in the bunches. What should I do? Also, are pine needles OK to put around things in the garden? Are they harmful as a mulch? I set my bell peppers close to the tree and they have done well. Mrs. O.B., Christiansburg
A: Your problem sounds like black rot infection. This fungus can be reduced by: 1.) sanitation - prune and remove from the area all the old shriveled black grapes left on the vine, as well as many of the old infected canes (look for black lesions); and 2.) six to eight thorough sprays of a good home fruit spray mixture that contains a fungicide for black rot prevention. This should be stated on the label or leaflet that comes with whatever brand of spray that you buy. For black rot prevention, the first spray should be applied when the new grape shoots are 1 or 2 inches long.
Pine needles do not make good mulch in the conventional garden because they don't decompose fast enough to be tilled into the soil by the end of the growing season.
Q: I am buying a vacation/retirement home in Ocean City, Md. Around the foundation is a ground cover like prickly cedar, through which is growing a stand of thick grass. I would like to replace it with another cover. How can I kill the existing one? Mrs. N.G.L., Christiansburg
A: The existing ground cover plant is probably low-growing junipers, although without seeing a plant or at least a representative sample I can't be sure. Junipers can be eliminated by digging. The grass can be killed with two treatments of the nonselective plant killer glyphosate (brand names Roundup and Kleenup) when the plants are actively growing.
Got a question about your lawn, garden, plants, or insects? Write to Dear John, c/o the Roanoke Times & World-News, P.O. Box 2491, Roanoke
John Arbogast is the agriculture extension agent for Roanoke