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Don Kinzler, Published August 31 2012

Hortiscope: Japanese beetle likely culprit

Q: I planted a hibiscus shrub that gets flowers the size of a dinner plate. I’ve had the plant for three years. This year, it is much bigger and loaded with buds. I was so excited until I noticed the buds are yellowing and something’s eating the leaves. The leaves look like lacy Swiss cheese.

I sprayed the buds with Sevin, but I’m still seeing what looks like a strange type of beetle that I have never seen before. I know the beetles probably are eating the leaves, but why the yellowing buds that are falling off? I water it correctly and use Miracle-Gro.

Could it be the mild winter and very hot July? Thanks for your time and knowledge. (Putnam County, N.Y.)

A: This sounds like the work of Japanese beetles. Try to capture one or get a photo and send it to me. They have voracious appetites and are common in your part of the country. The yellowing and dysfunctional appearance of the buds could be due to thrips feeding on the buds before they open. Try using Orthene insecticide because it has contact and systemic activity.

Q: I have a 5-year-old raspberry patch. This summer, I had a bumper crop in terms of production. I have never had so many berries. However, instead of growing like raspberries, the majority grew more like little crowns on the stem piece that holds them. When I would go to pick them, the berries would fall apart in my hand. If I brushed my hand against one while reaching for another, it would fall off the plant. For about every regular berry, I had 10 to 20 of these crowns. On the up side, they did not have as many seeds and they were the sweetest they ever have been. The bees were very thick in the patch this spring.

Did they overdo the pollination? Would too much watering cause this? I cannot think of anything I did differently from other years. Now that the season is past, my husband wants to clean up the patch. Is it too early to prune the old growth out to make room for the new stuff that will come up in the spring? (email)

A: Raspberry crumble is a virus that caused the problem. The most common are raspberry mosaic and tomato ring spot. There is no cure for the virus.

If you can remember which plants exhibited this problem, eliminate them completely. Get the old canes cut back now and wipe out any plantings that may appear to be wimpy or weak. Glad that you otherwise had a banner year of fresh fruit to enjoy because there is nothing like it.

Q: I have a pin oak that grew from an acorn 38 years ago. It is a beautiful, tall, small-trunked tree. Last summer, the top third of the tree died after leafing out. We didn’t know what to do, so we left it alone. This summer, after a severe drought, the next third of the tree died.

This tree grew in a swampy area that usually is under water during April and May. Sometimes it takes until June before it dries up. We didn’t have any problems with standing water this spring or summer. Can this tree be saved? The bark and leaves look healthy. (email)

A: With two-thirds of the tree dead, I wonder how much more you are willing to tolerate a disfigured tree before you decide it should be removed and replaced.

If what is there looks good, then the tree has a chance to survive. However, it won’t have the typical form of a pin oak. You might be better off collecting another acorn and planting it.

Q: I had a septic system installed in Morton County. The area where the septic system was installed was covered with native prairie grass. The soil is sand.

Now that the septic system is installed, the area is barren and the sand drifts during windy days. I would like to seed it into a native grass again. What kind of grass seed do you recommend and where can I buy it? How would I spread the seeds? Would a lawn fertilizer spreader work? What could I use to cover the area once seeded to keep the wind from blowing away the seeds? Is there inexpensive netting available? Thank you. (email)

A: There are many options to consider. Buffalo Grass can become established using plugs. Mixing the seed with blue grama would be using two native grasses.

Turf-type tall fescue would be a singular species that would do the job. Fairway or Ephraim crested wheatgrasses are adapted to dry or low-precipitation areas.

Western wheatgrass also is a good one to consider because it forms strong rhizomes to cover and hold sandy soil in place. How to apply the seed depends on the type of seed you are using. Hydromulching is the best approach because it holds the seed in place while it goes through germination and establishment.

Otherwise, a standard spreader would do the job. You can cover it with a decomposing, coarse-weave burlap that is staked in place. Where you would purchase the seed depends on the area to be covered. If it is just a couple of thousand square feet or less, then the local garden centers may have the seed or can order it for you. You might try a farm supply store for larger quantities or even for the smaller amounts.

Q: How does one control or get rid of the knob weed that infests my lawn almost every summer? I have pulled a lot of it, but I’m losing ground. How does it regenerate? The roots are a foot long on the plants that I have pulled out. Is there a spray that I could use? I know you have said that they grow in compacted areas, but I find them all over. (email reference)

A: This very persistent weed is difficult to control once it gets a foothold. It is most vulnerable at the young seedling stage. You can use a broadleaf herbicide shortly after emergence. Any that are listed for control of dandelions or plantain will do the job. Because of the very high seed production, repeat applications may be necessary. Additionally, good cultural practices will help squelch this weed. This includes overcoming compaction with core aeration on a regular basis, maintaining good fertility to keep the grass growing vigorously, and accepting the fact that compaction is bound to exist no matter what tactic you attempt. You also could make the compacted area a nonliving surface of sidewalk or walking path.

Q: I have a rocky mountain juniper on the east side of the house. It is shedding needles like crazy from the interior of the tree. Is this a normal part of the growth process? If there is something I need to do, I figured you would be the guy who’d know. Any information would be appreciated. (Turtle Lake, N.D.)

A: As long as the exterior growth is normal in appearance, this internal shedding is nothing to worry about. Trees, including evergreens, will shed their oldest, nonproductive foliage when conditions are severe. I would say that July would qualify.

Q: I have a question about pear trees. Last year, we moved into a home with a large pear tree that was full of fruit. It continued to bear fruit faster than we could pick them. We loved it. We were amazed after the incredible drought we had in eastern Texas last summer. This year, we had an exceptionally mild winter. The tree flowered beautifully and produced a small amount of pears in the early spring. Now it’s August and there is nothing at all. I read that there must be two pear trees close to each other. We only have one tree. It was struck by lightning many years ago and pulled together with wire. The wires are grown into the tree. I do feel like it needs to be cut back some. The branches are large and full, but I wanted to be sure to contact someone who truly knew how to do it. What are your thoughts as to why it isn’t producing? We were so looking forward to our pears this year! (email reference)

A: Overproduction one year leads to no production the following year. It will come back to a bearing cycle next year. Contact your local Texas A&M Extension Service agent to get some advice on pear tree pruning. Go to http://counties.agrilife.org/ and click on your county to get local assistance.

Q: I noticed that you take questions, so here is the question. I bought three acres of wooded land. After 36 years in Wyoming and Montana, I was sick of the wind and am back to my birthplace. In the woods are white pines, and I came across a burr oak. I’m sure it is a burr oak because of its extremely rough bark. I have received different answers to my question. The original tree was cut down and a back hoe dug right at the side of the old stump. The stump and roots are dead. However, a sucker has rooted that is 16 to18 feet tall and is a real nice tree. Some have told me that a sucker won’t live. Because of its size and root base, I think this is a new tree the same as you’d buy from a nursery.

As slow a grower as a burr oak is, I would love to save the tree because I am going to fill in the hole as a natural wooded area, so I would like to locate the tree closer to the house. At 68 years of age, I know I won’t see a mature tree. (New Holstein, Wis.)

A: This is a permanent tree in its present location. Surviving suckers eventually will grow into mature trees and it sounds like this one is well on its way. However, you need to wait until it is dormant before moving it. Have a tree spade operator with the largest spade available move it this fall after the leaves have dropped. I doubt that you could dig a big enough root ball and haul it over to the new site yourself. Good luck and enjoy this beautiful tree as it continues to grow at the new site.

Q: I just had a producer call and was wondering what is wrong with his sand cherries. Every year at this time, the leaves get yellow spots and then turn brown. He also stated that they never have produced berries. Any information would be greatly appreciated. Thanks for your help. (email reference)

A: Sand cherries don’t live very long, so I usually don’t like to recommend them as a permanent planting in a landscape setting. After 10 years at best, they decline with diseases and eventually die or the frustrated owner digs them out.

Why this one never has produced any fruit could be anybody’s guess. Because they haven’t, and with the disease problems you describe, the plants should be removed and replaced with something better.

Q: A woman brought in a few of her grape leaves that have some discoloration.

She is wondering what the cause may be. She has caterpillars in the plant, which have been eating most of the leaves, but the ones that remain look like what you see in the pictures. Is this related to the caterpillars or something different?

Will her grape vines come back next year? (Extension Service reference)

A: This is a combination of problems. It is a very bad case of powdery mildew and herbicide drift damage. In all probability, her grape vine will regrow next year, but she needs to clean up all the fallen leaves this autumn and cut the vine back in early spring to get any contaminated wood removed. She also needs to spray with a Bordeaux mixture to help control the disease as the leaves unfold.


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. For answers to general horticultural questions, go to http://www.ag.ndsu.edu/horticulture.