Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SUNDAY, March 31, 1991 TAG: 9104010323
SECTION: HOMES PAGE: E-5 EDITION: METRO
SOURCE: John Arbogast
DATELINE: LENGTH: Long
A: It sounds like you're familiar with the problems caused by black walnut trees. It is the roots of this walnut that produce the substance called juglone that is toxic to tomatoes, potatoes and related vegetables. The roots of the black walnut spread much farther from the trunk than those of other trees. Even after a black walnut has been cut down, the toxic substance can remain in the soil for at least two years, thus preventing the growth of those susceptible vegetables.
To deal with this problem, try growing vegetables in raised beds with at least 15 inches of soil depth. Add as much organic matter as possible to that walnut soil to encourage healthy soil microbial populations that can metabolize toxins and return the soil to a beneficial state as soon as possible. And/or grow garden crops in that area that are not susceptible to juglone, which means veggies other than tomatoes, potatoes and their relatives.
Q: When is the best time to cut back a climbing rose? This is an old one and I would like to prune it back a lot. Roanoke
A. Suggested time for pruning any roses should be based on the flowering habit of each rose as well as the growth type. I'm assuming your climber is one of the old ones that has abundant blooms for a few weeks in the spring or early summer, then blooms only sporadically after that until frost. To enjoy the most flowers on this kind, prune after that main bloom period. Cut back the long canes so the plant can be secured to your trellis and also to stimulate the growth of side shoots. However, heavy pruning may stimulate excessively vigorous shoot growth that may not bloom well and could quickly overtake the space.
Q: Someone we know has had his dogwood trees sprayed with lindane for borers four times in the last year. Is this excessive? Will their neighbor's garden vegetables, which are about 15 feet away, be affected by the chemical, either through the ground water or otherwise, or will the wildlife (birds, squirrels, cats and beneficial insects) be harmed from the spraying? The sprayer jokingly said the neighbors were getting the advantages of the residual spray. Children can be kept inside for the spraying, but animals or the garden are at risk. Is this a concern? Is there an alternative to lindane? Anonymous
A: The use of chemicals has become a sensitive subject. Lindane is recommended for borer control, and the times recommended by Virginia Tech for applications are in mid-May and then repeated two or three times at six-week intervals. So, I couldn't say that the person sprayed excessively just because it was done four times. What could be a concern is the amount of chemical used (did the sprayer follow the label and use only the amount suggested) and the manner that the application was made (applied only to the target and not up in the air and all around).
Assuming that the spray was made for dogwood borers as a directed application only to achieve bark coverage and that the right amount was mixed, I don't believe the neighbor's garden was threatened. Of course, the sprayer's joke implies that common sense and care may not have been used.
It is true that beneficial insects are killed whenever pesticides (chemical or otherwise) are used. Harm to non-target life forms due to pesticide applications usually results from misuse of that pesticide. Every pesticide label must include a statement about hazards to the environment, which should be read and complied with. This is an Environmental Protection Agency requirement to prevent the concern that you have raised.
Suggestions are printed on the label, telling how the product may be used without risk of injury to non-target animals or plants. This is why Extension folks and others constantly tell people to read and follow the pesticide label.
The best alternative to using lindane for borers, particularly for dogwood borers, is to keep the trees healthy with strong growth and prevent any kind of bump or wound. Dogwood borers seemed to be drawn to dogwood trunks that have exposed wood from injuries such as those that lawn mower bumps cause. It is possible to fish tree borers out of relatively shallow holes by inserting a fine, flexible wire, but this is not a very precise job.
Got a question about your garden, lawn, plants, or insects? Write to Dear John, c/o the Roanoke Times & World-News, P.O. Box 2491, Roanoke, Va. 24010.
Gardener's checklist
Jobs to be done the first week of April:
The increased sunlight coming through windows this time of year usually means house plants will be making new growth soon. Thus, it is time to resume monthly fertilizer applications. Any soluble "house plant food" can be used as long as the directions are followed. Too much fertilizer on potted plants will cause an accumulation in the soil and result in root burn and plant death.
Grass has resumed growth. Lawns can be managed for their best growth by mowing often enough so no more than one-third of the grass height is cut in one mowing. Allowing the grass to grow tall and then mowing short causes shock and injury to the roots. In the spring when the grass is growing rapidly, frequent mowing is required. Be sure your mower blade is sharp.
by CNB