NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
October 7, 1999
Ron Smith, Extension Horticulturist
North Dakota State University
Q: We have two ornamental crab apple trees in our backyard which have been losing their leaves all summer and are now almost bare. What is the problem and how do we treat it? We would hate to lose these trees! (Milbank, S.D.)
A: Your tree has apple scab--Ventura inequalis--which is brought by rainy, humid weather and host susceptibility.
First, clean up all fallen leaves and fruit this fall. Then, next spring before leaf-out, spray with lime-sulfur. After leaf-out, begin a program of spraying with Benomyl or Captan on a 10- to 14-day cycle during vulnerable periods--wet, humid weather.
If all of this is too much, then simply replace the tree with a resistant cultivar. There are plenty to choose from.
Q: Could you identify the enclosed weed for me and tell me how to get rid of it? (Pelican Rapids, Minn.)
A: It is crabgrass. Apply any of the following products next spring when lilacs bloom: Acclaim, Dimension, or herbicides that contain DSMA, Dacthal, Betasan, Balan, pendimethalin, or Tupersan.
Q: What is the correct way to grow garlic? I have some of the small leaves that grow on top of the long stalk, above the ground. If I plant them, will they produce garlic? Bigger ones? (Jamestown, N.D.)
A: Yes! Plant them around Oct. 10, about 3 inches deep. Next year, select the largest bulbs, and separate out the cloves, and plant again in October. Garlic is generally harvested at the end of July or early August.
Q: I have a cluster of four red oaks and a twin oak in my yard that are losing their leaves very fast. (Detroit Lakes, Minn.)
A: You have a couple of things going on. Most likely is a change in the water table. If it is coming up, that could cause the defoliation you are witnessing. And second, the leaf spots are a fungus known as Marssonina martini. Severe infections can also cause defoliation.
The best control is to practice good sanitation this fall by cleaning up all fallen leaves. It would be a good idea to spray the trees next spring before the leaves come out with lime-sulfur, as this is an excellent sanitizer.
Q: I have questions regarding two problems. Problem No. 1 is something that is growing in our yard. Problem No. 2 is something that is taking over my sister's flower garden. Could you please let me know if these are plants that we should destroy and how we should go about doing it? (Cogswell, N.D.)
A: No.1 is crabgrass, an annual you can treat with a pre-emergence herbicide. Number 2 is Russian knapweed, a tough, persistent perennial that will require Trimec being applied a couple of times per year to eliminate from the lawn. Now is a good time to start.
Q: I have wireworms in my house really bad. The fall or late summer and early spring months seem to be the worst time for them. They are all over the basement and are now coming onto the main floor. What can I do to get rid of them? I have tried spraying around the outside of my basement with malathion and have used diazanon, but neither seems to help. (Holabird, S.D.)
A: If you have this kind of problem, you need a professional exterminator. Wireworms are the larval stage of click beetles and are heavy feeders on potatoes, bulbs, seeds, etc. They are attracted to damp environments.
Get someone who is licensed and registered to apply pesticides in and around human residences. Diazanon is one of the insecticides suggested for their control, but unless it is properly applied, as it should be by a professional exterminator, it will only have limited effectiveness.
Q: Can I prune my pink potentilla bush round? If so, when is the best time to do that? Also, when should I separate my daylilies? (Ayr, N.D.)
A: Best time to prune potentillas is early spring before they leaf out. I don't recommend pruning them to a "round" form. Simply cut out the oldest canes at the base of the plant. A natural shape, which the plant will try to maintain anyway, is more attractive and healthier for the plant.
Daylilies can be separated either this fall or early next spring. Plant them at the same depth they were originally.
Q: Can you tell me what is causing the leaves on my flowering crab to turn brown and fall off? Someone told me it might be fireblight, but I am not sure. (Devils Lake, N.D.)
A: Your apple may indeed have had fireblight, but it also has some type of leaf spot fungus. Which one, I cannot be sure without a lab test. Basically, you should clean up all fallen leaves and fruit this fall. Spray next spring with lime-sulfur before leaves come out, and follow up with Captan or benomyl.
Q: Enclosed is a leaf from a Linden basswood tree. I just planted it last year, and this year it appears the leaves are full of rust or fungus. This has occurred in the last few weeks. There was no sign of it earlier. Is it serious? What can I do this year or next to prevent this happening again? (Portland, N.D.)
A: You have a couple of things wrong with your tree: scorch along the leaf edges and Cercospora microsora--a leaf spot fungus. I am also concerned about the size of the leaves. I suspect that your tree may be planted too deeply. If this is the case, dig it up and re-set it this fall or next spring while it is dormant. This action alone may correct the problem.
Spray the tree next spring with a lime sulfur mixture before it leafs out. Then follow up with Captan or Benomyl after the leaves have unfolded. But I encourage you to seriously check the way the tree has been planted. If improperly done, or planted too deep, all the spray in the world will not make a difference.
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 firstname.lastname@example.org .
NDSU Agriculture Communication
Source: Ron Smith (701) 231-8161
Editor: Dean Hulse (701) 231-6136