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Ron Smith answers questions about flowers, trees, gardens and shrubs.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a pine tree that is oozing a waxy substance. There is so much of it that the rocks beneath the tree are shiny. I also noticed that the branches are covered with little black bugs. They look like they might have wings, but none of them are flying. The tree looks wet from the waxy substance and draws many flies. Do you have any idea what these insects are and how to fix the tree? (e-mail reference)

A: The insects can be positively identified only by a visual inspection. The insect world is filled with too many lookalike characters to indentify from your description. What is oozing is the sap these pests are feeding on because it is a carbohydrate-rich material. The best way to control them is to visit a garden supply store and see if you can find some Bayer Advanced Tree and Shrub Insect Control. This is Merit (imidacloprid), which is very effective at controlling any plant feeding insects. Be sure to follow label directions when using this material. It will call for a particular dilution and for the application to go around the base of the tree. Done properly, the effect of this insecticide will last up to 12 months. It needs to be absorbed into the vascular system of the tree so when the insects feed on the sap, they are killed. It will take two to three weeks before the insecticide kicks in. It depends on the rate of growth of your tree. If you want faster effects, there are a number of insecticides on the market that are direct-kill products, such as those that contain Malathion.

Q: I have a question about a cherry tree I have. I know I can bake the cherries or eat them, but I do not know when to pick them off the tree. I have no idea if I should spray the tree or what else to look for. I also don’t know how to get rid of birds that are eating the fruit. (Spokane, Wash.)

A: The best way to tell if the fruit is ready to be picked is to taste it! It's a good sign that the fruit is ready when the birds become excited and start invading the tree, but often it is too late for you to enjoy the fruit because the birds eat the fruit in a wink of an eye. There are a number of harmless approaches to getting rid of the birds. Hang old aluminum pie tins from the branches throughout the tree. Purchase an artificial owl that is stuffed or filled with helium. Other methods include using balloons or rubber snakes to scare the birds away. Use all or any of these tactics well before the fruit begins to ripen. It’s a good idea not to use any sprays on the fruit unless insect or disease problems become unbearable. I advise you to get a professional arborist to prune the tree early next spring before blooming to maintain the health of the tree.

Q: I have been given a couple of offshoots of a fruiting avocado tree to plant in my yard. Am I likely to get fruit from the offshoots once they are established? Do I need to plant more than one? (Tampa, Fla.)

A: Avocados are self-fruiting. The fruit from a single tree usually will be sufficient. For heavier fruit set, even from fruit trees that are touted as being self-fruiting, the fruit load is increased significantly if another one can be planted nearby, usually within one-fourth mile.

Q: I read on your Web site that to get rid of crabgrass I should apply a pre-emergent after the forsythia but before the lilacs bloom. Is this true for granular pre-emergents or should I put granular material down a little earlier to allow it to dissolve into the soil? (Hudson, Wis.)

A: You can apply the material now because you are close enough for it to work. The recommendation is to keep it from being applied too early and carried into the soil too deeply for it to be effective for controlling crabgrass. Most of the seed is in the top inch of soil. The objective is to catch the seed at the right temperature when it is just becoming physiologically active to begin germination. The herbicide then nips it in the bud!

Q: We were hit hard in 1997 and again this year with Wild Rice River flooding. We are going to haul in clay and build up the slope to our house on all sides. We then will landscape. However, what should I do with the perennials that I have around the house (tulips, bleeding hearts, clematis, daisies, columbine, lilies, autumn joy, lamb's ear and irises)? Should I dig another flowerbed to store them and then replant in the fall? I have invested so much money and time into these lovely plants, so I would like to save as many as possible. About the clay, do I start again trying to build good soil as I have done through the years? (Christine, N.D.)

A: That is about all you can do. Try digging out the plants going into the evening hours or during cool or cloudy weather and then hope for the best. Anything you can do to delay the process until the plants are dormant would help the plants fare better than if you dug them out while in flower or during active growth.

Q: We are in the process of building raised beds for vegetables, strawberries, blueberries and flowers. We have 4- by 6-foot pressure-treated timbers that we are going to stack and drive rebar through and into the ground. The area would be lined with black plastic and filled with dirt. We just read that pressure-treated lumber should not be used for growing produce. Is there a chance that the produce could become contaminated? We really want to use the timbers that we have cut and drilled. If they aren't good to use for produce, can they be used for flowers? Should we use sterilized soil for the beds? If so, where can you get sterilized soil? Should the bottom of the beds be lined with plastic as well as the sides? Will drip irrigation work well with raised beds? (e-mail reference)

A: The treated timbers contain ammoniated copper arsenate. As far as I know, the timbers containing ammoniated copper arsenate are not cleared for use in planting vegetable gardens. However, the fact that you are lining the planters may negate any possible impacts from this material. I would suggest that instead of using black plastic, you consider using pool liner material because it tends to be more resistant to tearing. If you cannot find a suitable pool liner material, then go with either heavy-duty plastic or double line the sides. For flowers, there would be no problem. Also, you don't need to go to the expense of using sterilized or pasteurized soil. However, be sure to get sandy loam soil that drains well. With container gardening, pasteurized soil is strongly suggested for it to be successful. The bottom of the beds should be open to allow for the complete leaching of salts and any preservatives. Drip irrigation is the way to go and easy to install! Be sure to include a mechanical or electrical timer so you don't have to remember to shut the system off. You might want to contact a lumber company to get details about the potential toxicity in handling treated lumber and find out how it affects the environment. You also might want to check this site at for some facts about treated wood and the alternatives.

Q: I want to start some raspberries. Your Web site recommends using boyne and killarney. Can the two varieties be planted in proximity? Also, I have many chokecherries trees at the family farm. During the last several years, they have been hit hard by black knot fungus. It's bad enough that many trees are dying and none produces fruit very well. Most of the trees are in a shelterbelt and are 20-plus years old. The trees form a rather dense thicket that is not cleaned very easily. If I cut the trees back to the ground and clean up the area as well as I can, will they come back? If not, can I start new ones and contain the fungus with regular thinning and the use of some sort of fungicide? (e-mail reference)

A: No problem with growing them in proximity. It is done all the time. The chokecherries will come back with robust growth from the roots. However, that is assuming the trees were alive when you cut them back. You will not be growing single-stem trees. Instead, you will have rampant shrub-type growth. You can control the fungus from coming back if you maintain a regular, protective fungicide regimen.

Q: I have a couple of questions about growing vegetable plants in pots on the patio. I have a large pot and was thinking about planting a tomato and pepper plant in it. Is it OK for these two plants to be in proximity? To produce good tomatoes and peppers, does the temperature need to be quite warm? Finally, have you ever heard of diluting Epsom salt and adding it to vegetable plants? I found an article that says Epsom salt, when diluted and sprayed over tomato plants, will enhance fruit production and leaf growth. (Anchorage, Alaska)

A: Epsom salt may or may not improve tomato and pepper production. It depends on whether there is a magnesium or sulfur deficiency in the soil. In 99 percent of the cases, it certainly will not hurt the plant at the recommended rate, so you have nothing to lose by trying. It will not hurt the tomato plant to be sharing the same pot with a pepper plant. Replacing excess sodium in the soil with Epsom salt will work in part because the magnesium ion is divalent, while the sodium ion is monovalent. The magnesium will "bump" the weaker sodium off the soil sites to be leached with the percolating water. Good luck with your gardening in Alaska. Keep the plants in as much direct sunlight as possible.

Q: Last fall, I pruned my beautiful lilac bush. This spring, I'm finding that the branches are being stripped of their bark. I’m losing one to two branches a week. What is happening? I don't want to lose this bush. Can you help me to take care of this? (Chicago, Ill.)

A: Some rodents, probably squirrels, are doing this. Get some hot pepper spray and douse the branches with it. Whatever it is that is causing this damage, the pepper spray will stop them in their tracks. Unfortunately, the rodents will find someone else's plants to pick on!

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

NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161,
Editor:Rich Mattern, (701) 231-6136,
Prairie Fare: Prairie Fare: De-stress with Gardening  (2019-05-23)  According to researchers, gardening can be beneficial for mental, physical and social health.  FULL STORY
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