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Published October 21, 2011, 12:00 AM

Hortiscope: Managing grapevines both art and science

Q: I have severe pine needle scale on my spruce trees. Today, I noticed the males were in flight, so I’m guessing this is the second generation for the season. Is it too late for a systemic drench application? What product is the most potent systemic to use? There seems to be several brand names with different active ingredients. I have access to professional-grade chemicals.

By: Don Kinzler, INFORUM

Q: I have severe pine needle scale on my spruce trees. Today, I noticed the males were in flight, so I’m guessing this is the second generation for the season. Is it too late for a systemic drench application? What product is the most potent systemic to use? There seems to be several brand names with different active ingredients. I have access to professional-grade chemicals.

Thank you in advance for your help. (Mackay, Idaho)

A: At this time of the year, it is too late for a systemic to be effective. If you have a means of reaching the top with a sprayer, an application of horticultural or Neem oil would be the way to go. Early next spring, use Bayer’s Imidacloprid around the base of the trees following label directions.


Q: I came across a post by you on the Internet. It sounds like you are very knowledgeable about grapes, so I hope you could help me. I have some concord grape (I think) vines that are about 30 years old. The vines grow great every year but the fruit fails to thrive. Most of the grapes stay small and green, but a few will turn purple. I am new to grapes and would love to get these vines to produce. Can this problem be caused by too much shade, lack of pruning or fertilizing or old plants? Any information you could give me would be appreciated. (email reference)

A: It is very likely due to an overly vigorous vine and too much shade. The fruit suffers when vegetative growth is rampant. Annual spring pruning before new growth begins and then an early summer pruning is needed to reduce the amount of foliar cover. This will keep the plant in check and produce fruits that are harvestable. It also could be that your vine is at the edge of its hardiness zone. This could account for the grapes not ripening in time to harvest. Managing grapevine growth to be able to harvest edible fruit or fruit fit for making wine is both art and science. It requires that individual owners apply what science they know to growing grapes and then use the art of observation to react to what has been applied so adjustments can be made. You might want to refer to a University of Minnesota publication about growing grapes for home use. You can find it at http://goo.gl/UqrJA.


Q: I have a spider plant that has worms as roommates. The worms are gray. What should I do? I have other houseplants and don’t want them getting any bugs.

Please help. (Des Moines, Iowa)

A: The first step in controlling insects on houseplants is to pick them off if possible. Knock the plant out of the pot and completely clean the container or get a new one. Rinse the foliage and crown with tepid water and then replant using new potting soil. If more show up after this treatment, then some eggs were laid and have hatched, so you need to get an insecticide to keep them from multiplying.


Q: I have a question regarding what I believe is an October glory maple tree in my front yard. Some of my neighbors also have the same species in their yards.

The trees turn bright red in the fall. However, my maple tree turns yellow in the interior and then toward the outside edge of the tree as the weeks progress.

There are some random red or rust leaves throughout. Also, the final foot of each branch of the tree remains green, while the rest of the tree is yellowing.

Does my tree have some sort of disease? Could it be poor soil conditions? I fertilize it with tree spikes every year and it seems healthy. Please help. (email reference)

A: You should not be fertilizing your tree every year, especially with fertilizer spikes, because they are a waste of money. I would encourage you to cut the sod away from the base of the tree trunk and put in a 3-inch layer of organic mulch. Core aerate your grass under the tree or the entire lawn. There also is a possibility that your tree was mislabeled at the nursery. It does not have the same architectural form as your neighbor’s tree. Look closely at the leaves of both trees to see if they are the same. I’m willing to bet that you’ll see a marked improvement in this specimen by following through on my suggestions.


Q: I live in Germany because of a position with the U.S. government. The house we rent has 30 or more arborvitaes that must be at least 15 years old. The home is in southern Germany, so the climate is somewhat mild. The arborvitae plants have numerous brown spots. In some cases, the entire branches are brown, so the plants look very blotchy. More brown spots are appearing all the time. I have looked at the problem areas closely and don’t see any insects. I also don’t see any mold or anything on that order. Before I arrived last year, four of the plants next to each other died. Another one has died since then. I checked with one of the local nurseries about what to do. The suggestion was to cut the bad branches off and lightly feed the plants in the spring. While cutting seems good, I would like to be more proactive. Can you offer any advice or insights into this problem? If not, can you tell me where to look? (email reference)

A: Without seeing any photos or a direct sample, I only can guess that the problem is arborvitae leaf miner. Generally, leaf miner damage is limited by severe climatic conditions, such as we have in most of North Dakota. These are extremely small larvae. Leaf miner damage often is passed off as winter desiccation or drought stress. To confirm the problem, you need to have a magnifying glass to look for active larvae or exit holes. The adults are small moths that are silvery. Control is most effective using a systemic insecticide, such as Imidacloprid (Merit), which may or may not be available in Germany.


Q: I have a Chinese elm tree that is about 30 years old and 45 to 50 feet tall.

This fall, I heard a sound coming from inside the trunk. It sounds like a baby woodpecker. It is not a gnawing sound like pine beetles make, just a muffled knocking. I have not noticed any kind of pests around on the tree and the foliage is full. I also do not see any bore holes. Would you have any kind of information about this? I know this sounds kooky, but it’s true. (email reference)

A: I get plenty of kooky questions, but this one ranks right near the top! If it isn’t an animal of some kind making that noise, then I don’t know what to tell you. It is possible that there is an opening near the top of the tree that something has crawled or flown into and is taking up residence for the upcoming winter. You might want to contact a local arborist to see if he or she can do a drilling into the area where the noise is coming from to find out if the area is hollow and what could be making the noise.


Q: Our neighbor has a forest of untended lilacs on part of his lot. How do we keep the lilac suckers from intruding on our garden? Do you know of any plants that inhibit lilac root growth that we could plant along our fence line? It’s a huge task cutting out the suckers, which is what we’ve been attempting to do. (email reference)

A: You are proposing a battle of the suckering lilacs, which doesn’t happen too often. You can do a number of things to fight the problem. Spray the invading foliage with Roundup or cut off the growth on your side of the fence and spray the cut surface with Sucker Stopper RTU, which is effective for one growing season. You also could get in touch with a BioBarrier contractor in your part of the country. Go to www.biobarrier.com to find a contractor in your area.

This would involve digging a narrow trench and installing the barrier. The barrier will last about 20 years, so it would be the most permanent solution.


Q: I was browsing your excellent Hortiscope site. I have a question that probably would be classified as a maple leaf problem. In the last week, I’ve noticed that the leaves are falling off many of the maple trees, but the leaves are green. We are at the point now where the trees are starting to show signs of fall colors. I’m curious why the maple leaves would be falling while still green. This is the first time I’ve ever noticed this. (Windham, N.H.)

A: Green-leaf drop is an indication of a hormonal imbalance within the plant.

Something has uniformly put the trees under stress enough to cause defoliation to take place prematurely. This could be drought conditions, sudden rainfall after a bout of very dry weather, sudden downward shift in temperatures or some other environmental impact, such as a gas leak. I would contact the utility to see if there was any kind of a gas leak event in the area. Generally, this leaf drop does not mean the trees are dead or dying.


Q: I’m looking for information on the fruit-bearing cycle of Ohio buckeye trees.

We have lived in our north Fargo home for the last eight years and have an Ohio buckeye in the backyard. I’m wondering if this tree goes through cycles on how much fruit it bears. It seems that this year we’ve had more than ever before.

Thank you in advance for sharing your wisdom! (email reference)

A: Any fruit-bearing tree will go through some kind of cycle. Some years, the fruit will be heavy and some not so heavy. It also is tied to the maturity of the tree and its environment. To put it in a nutshell (sorry for the pun), your tree is mature enough to bear a heavy load this year due to its maturity and where you have it on your property. That said, an unusually heavy bearing also could mean the tree is going into decline, so it is accelerating its ability to propagate new fruit to assure the survival of the species. If that is the case, you should be able to see that the tree is in trouble. You might see a dying of the crown, premature leaf drop, root rot, insect damage or some nonbiotic injury. Assuming the tree is in relatively good health, I would say sit back and enjoy this bountiful production, but don’t eat any of the nuts.


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 email ronald.smith@ndsu.edu.

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