NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
September 7, 2000
Ron Smith, Extension Horticulturist
North Dakota State University
Q: I have a question about what appears to be a fungus on some sweet corn stalks. At first small spots show up on the leaves. The spots are about 3 to 5 mm in diameter and of a light cream color. Later a fungus like growth shows up where the leaf and stalk join. This growth later becomes thickened and continues to spread along the main stalk. Is there any product that can be applied to control or prevent this? Last year I also had some problems with the formation of the dark smut. It has dark blue/black appearance. Do you have any suggestions about what can be used for this? Thanks again for your help. (E-mail reference, Faulkton S.D.)
A: That is known as corn smut or Ustilago maydis, for which there is no cure or useful spray. It occurs when the temperature is in the 80's and 90's, and we are experiencing wet, humid weather. It saps the energy from the corn plant, reducing ear development. The best way to handle this is to cut off the galls before they release the black powdery spores, plant varieties of corn known to be resistant to smut, and finally follow good garden sanitation, cleaning up all debris in the fall. Do not use manure in your soil if this continues to be a problem.
Q: I see your column is still going strong and it's still the most informative horticultural site I've yet been able to find. Anyway, I have a question. Last fall I bought a reddish dogwood tree and planted it in the middle of our lawn under some sycamore trees. In summer, it gets about 1.5 hours of sun. Lately, it looks like the leaves, what few there are, are burned. What could be the problem? For its first year, it didn't bloom much and now the leaves are burned at the ends, and many have dropped off. Help! (E-mail reference, Lebec, Cal.)
A: It sounds like the dogwood is non-adapted to the site you selected to plant it in. Dogwoods, with few exceptions, like a loamy soil, rich in organic matter and not a lot of push from fertilizers. If you have it planted in a lawn area, that could be the problem, as it should be "bedded" - that is, incorporated in with other sub-canopy trees and shrubs. The red dogwood is more sensitive than the white to environments - soil, wind, humidity, etc. I suggest you try again with a Cornus nuttallii, or the Pacific Coast Dogwood. It is native to your region of the country.
Q: I have been growing an avocado pit in water. It has many roots now and I wish to plant it in my garden. Someone has advised that the 1- foot plant now has to be cut halfway up, to encourage growth. Is this true? Please advise, many thanks. (E-mail reference)
A: If you cut the mainstem (there should only be one at this point) this will force branches to form, making a more compact and attractive plant. Be careful in moving it either to a pot or outdoors that you do not injure the root system.
Q: I was given three hibiscus plants and was told that they could be planted outdoors and all I really needed to do with them was to water once a week and cut them back flush to the ground in the fall. Recently, my mother gave me a huge hibiscus plant in a pot and told me to keep it in the pot and outdoors in the summer, and indoors in the winter! This plant is much larger and greener than the plants that I have outside. Should I be keeping them inside? How large will they get? (E-mail reference, Towanda, Kan.)
A: The hibiscus can be planted outdoors in summer and brought back in during the winter. It responds well to pruning back, like you said you did with the others. Summering these plants outdoors seems to invigorate them to help them make it through the winter months.
Q: Our blue spruce, which is about 2 1/2 feet tall, has some black worms on it coming out of brownish things attached to the end of several branches. What are these worms, how do we get rid of them and can our tree be saved? (E-mail reference)
A: Those are bagworms, with a Latin name bigger than they are - Thyridopteryx ephemeracformis. They can be controlled with Orthene, Bt, or Sevin. Or, simply hand pick and destroy.
Q: What is a good fertilizer for calla lilies, growing outside in a pot, with eastern exposure? They are in the sun from sunrise till noon. Secondly, now that they have flowered, and leaves are turning yellow shall I stop watering them totally till late September? (E-mail reference)
A: Now that your calla lilies are beginning to yellow, you do not fertilize or water any longer, as they are entering their rest period. Once they start coming out of this rest period of six to nine weeks, begin a watering and fertilizing regime once again, using any standard liquid fertilizer intended for houseplants (Schultz's is a good example) applying it every two weeks, increasing it to weekly as the flowers begin to appear. Continue until the flowers begin to fade. You can leave the dormant calla in the original container during the dormancy/rebloom period.
Q: Would you please let me know how I can measure the suitability of compost ("the maturity") and what kind of plants can I use in a screening test of the phytotoxic substances in the compost. Best regards. (E-mail reference, New Zealand)
A: The basic rule for compost maturity is the inability to recognize any of the plant parts that make it up, along with a clean, "earthy" smell, not something that smells septic. Toxic substances are very unlikely in a well-digested compost, but salts are sometimes a reality to contend with. A basic test would be to grow a tomato plant and corn plant (a sensitive broadleaf and "grass") to see if they proceed normally. If they both bite the dust, then I'd suspect soluble salts being high, and would recommend cutting it 50 percent (at least) with mineral soil, and repeating the same test. Keep diluting it until you have hit the point where no toxicity symptoms appear.
Q: If you have any info on drying hydrangeas, please send. We have five beautiful plants; we would like to dry some for enjoyment this winter. Thank you. (E-mail reference, Edmond, Okla.)
A: You couldn't have picked an easier one to dry. Simply collect the blooms you want on nice long stems, cluster into bundles of five or six, tie with a rubber band or twine, and hang upside down in a dark, warm, dry place (like a garage) for about two to three weeks until the moisture is out of the plant material. They are then ready to use as dried flowers in arrangements.
Some folks will spray them with hair spray to preserve them longer.
Q: We have a very large cotoneaster hedge. Could you give us information as to what type of fertilizer to use, and any other information that we might find useful? (E-mail reference)
A: Cotoneaster or other hedges very seldom need fertilization. I strongly suggest fertilizing to only a known deficiency symptom. Too much nutrient availability predisposes it to fireblight attack, so growing it slow and hardened is better than fast, soft growth. If you want to apply some anyway, I suggest a 5-10-5 material that you can sprinkle around the outer spread of the foliage of the hedge, LIGHTLY.
Q: I hope that you can help me. In front of our house is an apple tree that was here when we moved in. It has been in great shape and produces a lot of apples, but we noticed over the past couple of weeks that now that the apples are dropping off like crazy, and all of the leaves have yellow spots on them that go completely through the leaf. On the underside of the leaf where the spot is, there is a wart-type thing with spiny spores about a quarter inch long. I can't think of any other way to describe them other than say that they look like hairy warts. If you touch these spores, they disintegrate. Also, some of the smaller branches are falling off now. It is breaking my heart and I do not know what to do. Any suggestions? (PS - We had a HORRIBLE drought here last year, and I am wondering if this strange fungus is because of the drought?) (E-mail reference, Pennsylvania)
A: It sounds like your apple tree has two very distinctly different problems: Cedar-apple rust (the leaf description you gave so well) and either codling moth or apple maggot larvae feeding on the developing fruit. Check some of the dropped apples by cutting them open and see if there is a grub or larvae (or evidence of one having been there) feeding within. Either pest will cause the fruit to drop prematurely. To protect the fruit from further damage, rake up and destroy all fallen apples, and spray the apples remaining on the tree with Sevin insecticide at 10 intervals until harvest. This fall, be sure to pick up any apples that have dropped. Next spring, spray the apples with the same material starting right after blossom drop. The rust fungus can only be controlled next spring. If you have any junipers in your yard, check those early next spring for a gummy, orange-colored glob with thread-like structures. Pick those off and destroy before they can "germinate" and spread to the apple tree. This is a disease that requires an alternate host to succeed; apple to juniper; juniper to apple, with the greatest destruction being borne by the apple. This disease too, will cause premature leaf drop. To control, spray next spring when the flower buds turn pink, with a fungicide that contains ferbam or zineb. Spray again when petal fall is about 75% complete, and once again 10 days later. If that tree has been around for a while, it is likely to survive this intrusive episode of disease and/or insect invasion.
Q: I visited your website today, and am writing in the hope you will respond (even though I'm not from North Dakota). I live in Eastern Canada and have two Japanese ornamental cherry trees which are about 15 years old. For the last four or five years, both trees come out looking very healthy in the Spring, but within a month or two the leaves start turning brown/yellow and falling. While there are still healthy leaves on the trees, they have been substantially defoliated.
The condition seems to occur whether there has been little rain or copious amounts of rain, so I don't think that is a consideration. Can you shed some light on this?
A: No problem. I just returned from a trip to Canada myself - Saskatoon, to be exact. There is a disease in the eastern part of North America that resembles your rough description of what is happening to your trees. A fungus known as cherry leaf spot (Coccomyces hiemalis). Once infected, the re-infection can occur from leaf debris remaining from the previous season quite easily. The first step in controlling the disease is to rake up and destroy all fallen leaves this autumn. Spray the tree the following spring with lime-sulfur, a good, common surface sanitizer, while the tree is still dormant. After leaf-out and when the petals flower petals fall, spray with a fungicide containing captan or chlorothalonil. Respray twice more at 10-14 day intervals. This treatment should put this disease or any fungus disease in check.
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 email@example.com.
Source: Ron Smith (701) 231-8161, firstname.lastname@example.org
Editor: Gary Moran, (701) 231-7865