NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
July 22, 1999
Ron Smith, Extension Horticulturist
North Dakota State University
Q: What is Abend Duft or night-scented stock? I cannot find it in my garden books. Is there another name? (Lengby, S.D.)
A: The night-scented stock is actually a Sweet William, of sorts.
Q: Can you tell me what is wrong with my juniper and my spruce? The juniper is more yellow than the rest of them that I have. (Pollock, N.D.)
A: I could find nothing wrong with your juniper sample; no spider mites, no environmental damage and no pathogens. I suspect that you may be looking at individual differences between plants or perhaps even a difference in species. Unless plants are cloned, differences in color, texture, rate of growth etc. are likely to exist.
The spruce has a bad case of needle cast. If the entire tree (or most of it) is in this state, there is little you can do, except remove the tree. If this disease is just starting, then there may be some hope of arresting the disease spreading any further. You can make twice-a-year applications of a product known as Bravo (chlorothalonil)--in May and again in June.
Q: Can you tell me why my cucumber plants are dying? (Marion, N.D.)
A: It appears the cucumbers are being hit by a disease known as verticillium wilt. This soil-borne organism will become active when it comes into contact with susceptible hosts--which it appears your plants are. My only recommendation is to remove the symptomatic plants as quickly as possible. Next year plant the cucumbers in a different location in the garden and be sure to select resistant cultivars.
Q: My mother has an African violet, and the base of the leaves are swollen. What causes this, and how can I cure the problem? (St. Paul, Minn.)
A: The swelling of the leaf petiole on African violets is most likely caused by a cyclamen mite infestation. Their feeding activity causes swelling and twisting of the foliage, and the entire plant is stunted with withered flowers. They should be detectable on the underside of the leaves, looking like specks of dust. Shake a leaf over a clean sheet of paper, and these "specks of dust" should move. Unfortunately, insecticides don't work. The only remedy is to dump the plant and begin anew.
If what I've described doesn't match up with the visible symptoms, then she must have a gall-forming pest that is uncommon on the plant. Cut one of the swollen petioles open and see if there is a small larvae housed and feeding in there. Again, the only course of action is to dump the plant.
Q: What can I spray my rose bushes with? There is something wrong with them. (Linton, N.D.)
A: Your roses have powdery mildew and rust fungi problems. You can control both with either lime-sulfur or fungicides containing triforine (Funginex). Repeat every 10 days, protecting the new emerging foliage. Try to avoid wetting the foliage when watering.
Q: I have two trees that appear to be the same growing in my yard. One flowers and gets fruit and one doesn't. Why? (Walhalla, N.D.)
A: A bird has planted some mulberry trees for you. The fruit will naturally attract more birds which means that more seed will be distributed. The ones that have not set fruit are likely males. If these showed up in my yard, I'd cut them out, as they tend to be quite messy.
Q: Can you tell me why these clusters of leaves keep falling off of my cottonwood tree? What should I do, and what is causing it? It hasn't been producing cotton either. (Emery, S.D.)
A: The defoliation you are seeing is normal for members of this genus. Nothing can be done about it if you don't want to remove the tree entirely. A cottonless cottonwood is a blessing. Rejoice, at least, in that fact!
Q: I have six seedlings, 3 to 4 inches high, of bur oak in a rubber pot. I don't have a place to plant them right now, and I am wondering where to keep them over the winter. (Tappen, N.D.)
A: I would suggest mulching the containers with straw or plunging them into the ground temporarily until sometime in mid-October.
Q: In our area we have had an outbreak of little green worms on our evergreen trees for the past three or four years. We sprayed them twice last summer, but we are wondering if we need to spray this year with such lush conditions. Should we just forget it and let nature take its course? (Tioga, N.D.)
A: Nature taking its course can sometimes be fairly brutal! So I don't necessarily suggest that approach. What I do suggest is a continuous monitoring of your evergreens to see if there is a population explosion of this insect, which I believe is a sawfly larvae. If the trees are otherwise vigorous and healthy, and the population appears light, then I wouldn't worry, as natural predators will usually move in.
However, if it appears that the insects are causing heavy damage and their numbers seem to be going up without a natural check occurring, then intervene with the appropriate insecticide--Sevin. Three or four years of heavy defoliation could kill the trees.
Q: I received seeds from someone who said they were hollyhocks, but I'm worried that they are weeds. Please don't tell me they are thistles! (Kent, Minn.)
A: Beware of those who bear gifts because what you have is light years from being a hollyhock. It is, in fact, sowthistle. Yank everything that looks like that out of your garden before it flowers, as each plant has the ability to produce more than 9,000 viable seeds!
Q: Our lawn seems to be the only one around with an abundance of white clover. We have tried to mow it, but that does no good. Is there anything we can do to get rid of it so it won't come back next year? (Orient, S.D.)
A: White clover used to be part of grass seed mixes when I was a kid. Then someone called it a "weed," and the battle began! Today there are many clover herbicides available. Refer to recommendations in the NDSU Extension Service publication titled "Weed Control in North Dakota Lawns" (H-1009). Products such as Trimec or Confront are herbicidal compounds that have a synergistic action which takes out clover. The best time to apply the herbicide is when the clover is actively growing, or in late August to early September.
Q: I have a pure-air plant and the leaves look as though they got burned from the sun, but the plant hasn't been sitting near the window. I also thought it was supposed to be hanging over the side of the planter, but it is 11 inches high and doesn't seem to be bending at all. (Carrington, N.D.)
A: Your "pure-air plant" is the spider plant--Chlorophytum. The burning you see is likely caused by underfeeding. Feed a little at each watering and the plant should take off for you. If the damaged tips bother you, cut them off.
Q: Can you tell me what is wrong with my peace lily? The leaves turn black and then yellow. (Fargo, N.D.)
A: I suspect it may be spider mite damage, although from the description in your letter, the symptoms don't fit. Check the leaf undersides by taking a piece of facial tissue and rubbing it along the undersides of the leaves. If you get smeared streaks, then it is likely mites. Mist the undersides for control.
You may also have the plant in a container that is not free-draining. If you do, go back and dump or pump out excessive water 30 minutes after watering.
Q: I have a flowering crab tree that blossomed this spring and now the leaves seem to be drying. Could you please tell me what is wrong? (Rolette, N.D.)
A: Your tree is suffering from a fungal disease known as apple scab. It is likely too late to do anything about it now, but you might rake up all fallen leaves this autumn, and spray next season with lime-sulfur prior to leaf break. As the new growth emerges, spray with Captan or benomyl.
Q: We have a plum tree where the fruit begins to grow then all of a sudden the fruit puffs up and falls off. What is the problem? We also have two apple trees that leafed out nicely, but now the leaves are shriveling up. We dusted with Sevin, but they are still sick looking. (Drake, N.D.)
A: The problem with the fruit on the plum is a fungal disease known as "plum pockets." Apply lime-sulfur in the fall after leaf drop or in the spring just before the buds break open.
The apple trees likely have a disease known as apple scab. Rake up all fallen leaves in the fall and spray next season with Captan or benomyl.
Q: Do you have any advice for people growing potentilla for the first time? (Box Elder, S.D.)
A: Plant them in full sun, water every two weeks if there is no rain and fertilize only when needed--which is likely never in average soils. Cut out oldest growth early in spring before leaf-out.
Q: Our two apples trees are dying. We thought it was wind damage, but now it looks more serious. Is there something we can spray them with, or is it too late? (Claire City, S.D.)
A: Your tree is being ravaged by fireblight bacterium. Prune and burn the diseased twigs this fall after several hard freezes. Spray next spring at blossom opening with Streptomycin antibiotic and again immediately after a damaging storm. In the meantime, try not to stimulate new growth as this is most susceptible to the disease.
Q: Could you tell me what is wrong with my flowering crab? Every spring it blossoms, but then the buds start dropping and no little fruit sets. (Faulkton, S.D.)
A: Your tree has a bad case of apple scab. Remove all fallen leaves and fruit this fall and spray next spring at leaf-out with Captan, a fungicide.
Q: I had three big Poplar trees cut down and the stumps ground last fall. Now I have little suckers coming up all over my yard. What would be the best way to get rid of them so they don't come back again? (e-mail)
A: This is a common affliction with poplars--also with chokecherries and plums. I apply a broadleaf herbicide like Trimec. This translocates to the roots which eventually kills them off. It will probably take a couple of years to get them all killed off, but there is really no other way. Make the application a day before mowing so that you have good surface area for absorption.
###
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