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Published August 19, 2011, 12:00 AM

Hortiscope: Willow tree could suffer from blight, canker

Q: I have some questions about a willow tree disease. A customer purchased some golden willows from us. Since planting them, he has found some glossy black patches on the bark.

By: Don Kinzler, INFORUM

Q: I have some questions about a willow tree disease. A customer purchased some golden willows from us. Since planting them, he has found some glossy black patches on the bark. The patches were not there when he planted them, so they have developed in the past few weeks. It doesn’t come off when rubbed. The trees are growing well and showing no signs of distress. Do you have any idea what those black patches could be? Any information will be greatly appreciated. (email reference)

A: This could be bacterial twig blight, black canker or something entirely different. These trees are very prone to insect and disease problems, so I don’t know why they are planted. Only a lab test could verify just what the pathogen might be.


Q: Could you please tell me what is wrong with my tomato plants and what I can do for them? The leaves are curling up and some stems seem to be getting weak. I do not see any pests on them. The tomatoes were planted in a new garden area this year. (email reference)

A: Leaf curling of tomato plants during the heat of summer is normal with many varieties. As to the stems getting weaker, I have no answer for that without more information.


Q: My flowering crab tree has a fungus that gets worse each year. Is there a treatment for this disease? Would you use Daconil or Fungisol? Is there some preparation I can use this fall? (Jamestown, N.D.)

A: Applying a lime-sulfur spray early in the spring before new growth emerges is a good general sanitizer. Picking up all the leaves and fruit this fall will go a long way in curbing this disease. Once the foliage has unfolded, you can spray the tree with a fungicide product containing chlorothalonil. It usually is found on the retail market under such names as “All-Purpose Orchard Spray” or something along those lines. Be sure to check label listings to be sure the concentration can be used on apple trees.


Q: I emailed you once before about my jade plant. It’s alive and healthy again.

However, when I water it, there seems to be tiny, whitish bugs coming up from the roots. How do I get rid of them? (email reference)

A: Those likely are fungus gnats. If you are so inclined, you can repot the plant using fresh potting soil. Be sure to clean the pot thoroughly before you repot. Another option is to have a nonaerosol spray of a houseplant insecticide handy each time you water to wipe out the population. These gnats are just an annoyance, not a threat to the health of the plant.


Q: This is the second year of gardening for me, which definitely is going better than last year. I had to rip all of my zucchini and cucumbers out last year because of powdery mildew. This year, the cucumbers look good, but I’m seeing signs of powdery mildew on the zucchini again. We’ve been cutting off the infected leaves before they get bad, but I’m noticing that the new leaves have a different shape. Instead of being big fanlike leaves, the new ones are growing more like tree leaves. In other words, the leaves now are like gloves and not mittens. Any ideas? (email reference)

A: Glad your zucchini plants are doing better, but don’t be too anxious to cut off the foliage. You might want to discourage development of the mildew with applications of a fine spray mist of water early every morning. While the fungus develops in high humidity and poor air circulation, it will be thwarted with sprays of water. Just be sure to do it early in the morning so the foliage has a chance to dry before nightfall.

Plant varieties of cucumbers and zucchini that are powdery mildew resistant and try to reorganize your landscaping to improve air circulation and sunlight penetration. Why the foliage is changing character is anybody’s guess. It probably has something to do with your removal of the older foliage as soon as the symptoms show up.


Q: Finding your column in my newspaper today was timely for my raspberries. This is my third or fourth summer of having raspberries. They grow straight for a few feet and then become heavy with berries and start to lean forward. Thinking that it would save the ones in front, we tied a rope between two stakes so the back rows stood up straight again. This helped for a time. However, we noticed this week that the stalks are drying up on the inside part of the patch, but remain green at the top and are bearing fruit. Also, as they got taller beyond the rope and stakes, they again hung forward and rested on the stalks in front. A couple broke with the weight of the branch where it leaned against the rope.

What advice can you give us for next year? My husband has talked about putting up some type of fencing product that would be stiff to hold up the stalks. Do you know of a good book that talks about growing and caring for raspberries? I love the flavor of my berries and we do get sufficient berries, but I think I could get more if they were able to get more sunlight lower in the patch. The patch is in sun until about 4:30 p.m., so they have lots of exposure. I water the plants often (maybe too often). I don’t really know how much water they need. Any advice would be welcomed. (email reference)

A: Go to http://www.ag.ndsu.edu/pubs/plantsci/hortcrop/h38.pdf for some beginning advice on growing raspberries. Raspberries do require a good deal of work. Stretching a couple of ropes along either side of a row will help keep them in bounds somewhat. You also need to do some thinning of the canes. Keep the stoutest ones for each bunch you intend to tie up, but no more than three or four per bunch. Of course, the old fruit-bearing canes need to be pruned out when they are done bearing. However, because of summer heat and mosquitoes, along with increasing yellow jacket activity, this usually is put off until a killing frost has arrived or early the following spring. At the time of old cane removal in the spring, the bearing canes should be cut back to about waist height to get them down to size. The thinner, puny canes should be removed entirely at that time.

If the fruit wasn’t so tasty and good for us, I doubt that most of us would go to the trouble of growing them. The delicious fruit on cereal and ice cream or incorporated into a pie, along with freezing some for winter consumption, makes one forget the sweat, blood taken by mosquitoes and the scratches we get from picking them.


Q: My phlox look horrible this year. There usually will be some powdery mildew, but this year the stems appear to be dying from the bottom up. The leaves of one plant were completely brown, so I cut it back and there is new growth coming.

However, I’m assuming it won’t bloom this year. I have phlox in different areas of the garden that seem to be afflicted to varying degrees. Any ideas on what is happening or a remedy? Some look so bad, I doubt they will bloom this year. The photo attached is one of the better-looking plants, but you can see the brown starting to move through the plant. Thank you for your help. (email reference)

A: This is going to be the year that phlox are going to suffer badly because of the hot, humid and rainy weather we’ve been having. You can attempt to blunt the impact with a regular spraying of a fungicide that has the active ingredient captan or chlorothalonil. Both are broad-spectrum fungicides.


Q: We recently moved from Michigan to Colorado. We find the plants, weather and soil foreign to us. We have an oak tree in the front yard that is full of leaves, but one-third of them are brown, dried and dead at the tips. The tree is adjacent to a sidewalk and the soil is hard clay. Any suggestions or diagnosis? (email reference)

A: You need to contact the Extension Service office where you live. Go to www.ext.colostate.edu/cedirectory/countylist.cfm to find your contact.

Someone locally can assist you with this better than I can from North Dakota.


Q: Just three weeks ago, I wrote and asked you about pruning our beautiful birch willow. You gave us the steps to proceed with pruning. The tree looked marvelous after a little trimming on the bottom branches. However, a storm hit this afternoon that made us so sad. It may be only a tree, but it is my delight, and this afternoon’s wind broke the tree in about the middle. Three large, young branches split off the trunk. We cut off the broken branches, but it left a large portion of the trunk exposed. You told us when we pruned there was no need to treat the cuts because no sap was flowing. How about this massive wound to our tree? Do we just wait and see or is there something we should try? (email reference)

A: Well, it is hard to give encouraging words to a hit like this. Instead of removing the tree at this point, I’d suggest just leaving it alone to see what happens next year. The tree will attempt to heal the wound. However, if the wound is large and ragged, it will be difficult for the tree to remain structurally sound. It may survive, but it may not provide the aesthetic impact you want. If that were the case, you would be better off having it removed and then replant.


Q: I have a red maple tree that is about 16 years old. It was in perfect shape the beginning of last year, but then it started to have dying branches. The treatment someone gave me for the problem did not work. What could be the problem? (Massachusetts)

A: You did not say who looked at the tree. I suggest contacting the Extension Service where you live to get some help. Go to http://

extension.umass.edu/index.php/in-your-community to find an Extension agent.


Q: I found your tomato information on the Internet to be very interesting. I have a large yard. Last year, we took down an old ash tree that shaded an area of the yard. Thinking that we now had a sunny yard, I planted some tomatoes. I put in six plants of five different varieties around Memorial Day. The area was previously lawn and the soil has some clay. I did not fertilize or prepare the soil. The results have been very disappointing. Of the six plants, only four have produced any fruit. The plants had many buds but produced only one tomato on each plant. The problem could be a lack of sun, but it is difficult to tell.

The area gets much more sun than it used to, but it may not be enough. There are tall trees in neighboring yards that block more sun than I was expecting. The area is in and out of direct sun many times during the day. Do you think the lack of sun or my not preparing the soil is responsible for the poor yield? (Chicago)

A: There are many reasons why tomatoes will produce poorly. Much of it has to do with night and day temperature fluctuations. It could be your night temperatures are too high for good fruit set. From what you said, I doubt that it is due to shade from neighboring trees. Just don’t give up!


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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