NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
June 22, 2000
Ron Smith, Extension Horticulturist
North Dakota State University
Q: We have a yellow poplar tree that is about 3 feet in diameter. I'm not sure how old it would be, but it has always been quite full, until this spring. Now half the tree is dead and on the other half the leaves are extremely small and the flowers are not filled out. We can't find any insects on the tree nor any sign of disease. What could have caused this? What should we do to revive this tree? (Dayton, Ohio, e-mail)
A: If the one side of the tree is really dead (no green cambium showing beneath the bark) then there is nothing that can be done. If there is some life there, then get an arborist to come in and fertilize the tree. Try to encourage new growth. But frankly, I'm sorry to say, there probably isn't much hope to save it.
I would also encourage you to have the tree checked for internal soundness, as I'm afraid that trees that large will often have a decaying center, causing the tree to be a physical hazzard to both property and body.
Q: I have an American bittersweet vine. Why doesn't it produce fruit like the information says it will? (Minot, N.D., e-mail)
A: You received the male instead of the female plant. This is primarily a dioecious species (separate sexes). You should have ordered a female clone as well. If you were promised a fruitbearing plant, you should try to get a refund from the nursery. Ideally, the plants are sold in pairs like holly, one female and one male.
Q: I need to know what to do with the dead tulip stems. (e-mail)
A: Tulip foliage needs to die out naturally. When it has yellowed completely, it should separate easily from the bulb with gentle tugging. If you remove the foliage too early, the bulbs will not flower next year. The foliage is making the food for that show next year right now, as long as it stays green. You can rubber band the leaves together and plant annuals around them in the mean time.
Q: We have a serious defoliation of oak trees this spring due to an oak tree worm that pupates in the leaves then rains down on webs to later become moths. Do you know about this phenomenon? (Southern California e-mail)
A: It sounds like you have a gypsy moth problem. These pests were imported into the United States from Europe in 1869 for possible use in silk production. Some escaped and have become entrenched as pests across the entire continent. Unfortunately, oaks are one of the favorites of these defoliators.
Sex traps (pheromones) will take care of future generations, and a biological, Bacillus thuringensis (Bt) sprayed before the fourth instar larvae appear will be effective in controlling the present generation without harming any other biological life in the area. Foliar sprays are largely ineffective because of their ability to penetrate the tree canopy.
If this is the first defoliation of the tree, don't worry, it will releaf again. But keep a vigil for these pests because repeated defoliations will kill the tree.
Q: My sister's 20-year-old maple tree has spots that are a crimson red color, flat and almost shimmery. Some of the leaves have turned totally red, as well, with just green veins showing. Is this a case of leaf galls? (e-mail)
A: The galls you are seeing on your sister's maple are quite common and harmless. These galls often come in three forms—bladder, spindle and erineum. Often they make a spectacular showing (dense and bright red ) and get the homeowner's attention. They are caused by mites that move into the unfolding leaves in early spring and begin feeding, thereby causing the abnormal growth that's visible. No sprays are effective nor necessary.
Q: Is there a simple or logical way to remove lichen on older gravestones? (Litchville, N.D.)
A: I would suggest a sandblaster. These portable tools are available for rent and do a good job of cleaning up old grave stones and iron work.
Q: I am hoping that you can help me save my 25-year-old evergreen trees. I have had to cut out several branches that were completely brown and dead. I have noticed some bluish-white waxy or sticky mixtures on the trunk and branches, and some has dripped down on the green shoots. I have also seen places where the clear sap is oozing out on the trunk and branches. Is there something I should spray them with? I had sprayed a few places with daconil, but I don't think that has helped. They are beautiful trees and I would really like to save them. (Milnor, N.D.)
A: It sounds like the symptoms of Cytospora canker. There is no spray. Prune out infected branches and dispose of them ASAP. Then try to stimulate the trees' growth with regular watering and fertilization.
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Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu.
Source: Ron Smith (701) 231-8161
ronsmith@ndsuext.nodak.edu
Editor: Dean Hulse (701) 231-6136