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Hortiscope

Ron Smith answers questions about plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have two hibiscus plants that I have indoors in pots during the winter. They have been blooming, but also have black, flying bugs. I've been spraying them with a dish detergent and water mixture. It appears to help for a time, but then the bugs return. Is there a spray that I can purchase for this problem? (e-mail reference)

A: Any spray I recommend would have the same impact. You might try locating a systemic insecticide that can be soil-applied to control them if they are nibbling on your plant. I suspect they are fruit flies. I know the name doesn't fit, but they aren't very bright, either! Fruit flies have very short life cycles. They are more of an annoyance than a threat to the plant. Otherwise, just keep up with the insecticidal soap as they appear. You eventually will win the battle!

Q: My apricot tree drips a liquid from its branches, especially the higher branches. It is driving me crazy. Last summer the tree gave us bags and bags of sweet apricots. Could you please tell me why that liquid is dripping from the tree? (Los Angeles, Calif.)

A: The problem could be borer, spider mite (very likely) or aphid feeding activity (also likely). I would tend to think the problem is spider mite feeding. There are sprays for that, but get a confirmation this spring when the tree leafs out and the problem is manifesting itself again, which it probably will. Contact the California Extension Service at http://ucanr.org/ce.cfm and click on the county where you live. A phone number and contact person should pop up. I'm sure that someone there could assist you in nailing down what this problem is and make recommendations that are more accurate.

Q: I live in California and have many black walnut trees in my landscaping. Is there a way to stop the trees from producing nuts? (e-mail reference)

A: There is a very good market for black walnut nutmeat. Are you sure you really want to do this? There are sprays that limit fruit set, but the timing is critical. You need to contact the California Extension Service in your county to get some local assistance. Go to http://ucanr.org/ce.cfm and click on your county for specific information from a horticulturist.

Q: I was given a spider plant as a gift a few months ago. Recently, the leaves have started to turn red. Do you know what could cause this? Is it being overwatered or too cold? (e-mail reference)

A: It could be caused by either one, but often it is a sign of some nutrient deficiencies. I would suggest repotting it in some pasteurized potting soil that is available on the market, such as Miracle-Gro. Use a free-draining container. When you water, only do it when the soil is dry and make sure water flows out the bottom. After 20 to 30 minutes, drain off any excess water remaining in the saucer. This should improve the plant without knowing what is causing the problem.

Q: We have what I believe to be a crab apple tree in our front yard. Recently, we had plumbing issues. The city came out and said our cleanout was below ground next to our tree. When we dug next to it, we had to cut three to four roots that were approximately 2 to 3 inches in diameter. Will this cause the tree to die? (e-mail reference)

A: It should not have a major impact on the tree if it was otherwise healthy. Removing three to four root sections the size you describe shouldn't be traumatic for the tree.

Q: We have an infestation of bagworms every year. To get rid of them, we have done everything from spraying the trees to picking the nasty little worms off. What are we doing wrong? We have eight very large white pines that were here when we bought the property. We planted 11 spruce and fir trees in the fall of 2007 and another six last November. What can we use and how should we use it? (e-mail reference)

A: Bagworms are difficult to control because often they are unnoticed until mature. Mature larvae often will pupate early if they detect pesticides on the plant foliage. Though there are a few known bagworm parasites and predators, they are not adequate in urban habitats to get rid of the worms. However, several options exist to control bagworms. Bacillus thuringiensis (Bt) is effective if used early enough in the season. Since you didn't tell me where you live, I can't be completely accurate with the date. In the upper Midwest, it is around the middle to the end of June. Doing it then will control the new hatchlings, which is the most effective. Using a chemical control gives you several options. Earlier applications are better than later. Some of the products available are Orthene, Sevin, Malathion and pyrethrum. How to use these materials is explained on the label. If you can, continue to pick off the bags you can reach during this dormant part of the season. Carefully cut the silk attachment to the branch because it has the potential to girdle the twig at that point in the future.

Q: I think one of my plants has scales. It's a plant I rescued without looking very closely at it. I scrubbed all the leaves and noticed it had many scale bug leavings. The leaves are mostly clean and I have applied a solution of water, alcohol, tea tree oil and dish soap to all visible parts of the plant. The recommendation from my local florist was to throw it out, but I can't do that just yet. Do you have any additional information about scale bugs? I don't know what the best resource online would be to learn more. Any help is much appreciated. (e-mail reference)

A: Scale insects are difficult to control once they get a foothold on a plant. However, with persistence, which you seem to have, it can be done. Washing the leaves was a good start. I encourage you to continue along those same lines. If the plant is manageable, place aluminum foil over the pot in a secure manner and swish the aerial part of the plant around in a tub of tepid water with a mild detergent added (about a tablespoon per gallon). If that doesn't work, look for products containing imidacloprid. It is a systemic insecticide that sometimes is found in potting soil or systemic insecticides on the market and sold by Bayer or Miracle-Gro. If you are loath to using any chemicals and the other nonchemical tactics don't seem to work, cut the plant back to a nub. Leave a stem about 2 inches long sticking out of the pot. Repot the plant in fresh, pasteurized soil and use a free-draining pot. Continue maintaining the plant normally with watering and light exposure. If it was otherwise healthy, there should be new growth coming up that would be free of any scale insects. If this plan doesn't work, then take your florist's advice!

Q: I have a perfection apricot tree that I planted two weeks ago. I need another apricot tree to pollinate it, but do not know of a variety that will have the same blooming season as the perfection apricot. Can you please tell me about two to three different varieties with the same blooming period? (e-mail reference)

A: You must live in California. The only tree that is recommended by University of California horticulturists is rival. None of the others will work and this one is not self-fertile. I'm surprised the nursery you purchased the tree from didn't tell you this. Are you sure that they didn't graft a pollinator branch onto the tree?

Q: I am looking for a fast-growing tree to plant in a row this spring that can act as a wind/privacy screen. My soil seems to be all clay below 2 to 3 inches of topsoil. I have found hybrid poplar, austere hybrid and willow hybrid while searching the Web. Would one be better than the others when considering soil and weather conditions or is there another tree that you would recommend? Should fast-growing trees be avoided? (West Fargo, N.D.)

A: Of the three you listed, hybrid poplar is the best bet. Keep in mind that poplars and willows are good for fast growth, but have the disadvantage of contributing a lot of kindling and some firewood to the landscape. For some people, this is intolerable. Another characteristic of poplars is their tendency to send up root suckers later in life in the most inappropriate places, which also can drive some people nuts. If neither of these characteristics is objectionable to you, then go for the poplar. For wind screening, a combo of evergreens, usually spruce, and deciduous plantings are used. The evergreens give more wind protection in the winter, while they both work in the summer. Before you make a decision, visit the local nurseries to see what they have to offer. Keep in mind that what you will be getting from online purchases will be small bare-root seedlings that someone has picked off a conveyor from a line of stock. If this doesn't bother you and you are ready to accept some loss in handling and transplanting, then order more than you need in case some don't establish for you. You always always remove any excess that starts overcrowding the setting.

Q: I am wondering why my spider plant hasn't produced any spiderettes. I have had it for seven years and it is doing quite well. I water it every week. The pot that it is in doesn't drain freely. The plant also doesn't want to spread as it should. As far as I know, it never has produced spiderettes and I'm curious to know why it hasn't. (e-mail reference)

A: It could be that you are taking care of it too well. Withhold water somewhat and don't fertilize the plant. All houseplants should be placed in containers that have excellent drainage. You might unwittingly be creating anaerobic conditions in the root area. This lowers the energy level of the plant that is needed to produce spiderettes. Your problem could be insufficient light or the wrong kind. Natural light coming through a window is best followed by fluorescent or grow lights. When spring arrives in your locality and the danger of frost is past, repot the plant in a free-draining container and hang it from a branch under a tree canopy. Adjusting these cultural practices will help get this plant around to reproducing.

Q: I have a clump/cluster of cottonless cottonwoods that were planted 10 to15 years ago (not by me). I live in the Rio Grande Bosque area near Jarales, N. M. The water table at my location is just less than 6 feet. Four of the trees need to be removed, but must be cut. Local officials don’t allow the trees to be moved. These are perfectly healthy trees, so it is not my choice to cut them. I have about a week left before they are cut. If we bore a hole into the water table, provide root hormones and then put cut 10-inch diameter trees into the hole, what are the chances the trees will survive? (e-mail reference)

A: Sorry to hear that you've run into a stone wall locally. While the cottonwood is a relatively easy tree to propagate from cuttings because of preformed root initials in the branches, I doubt that these plants would make it. A rooting hormone when dealing with trees this size would do no good, so don't bother. If you want to chance it, try it (assuming they are dormant now). Don’t use any hormones. I recall willow logs this size or larger that we used to put up a temporary barbwire fence in Georgia. The following year the logs sprouted. After we dug everything up, we found some roots developing. You might get a similar reaction to your effort, but I doubt they will survive. However, you have nothing to lose by giving it the old college try.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith@ndsu.edu.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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