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Don Kinzler, Published September 21 2012

Hortiscope: Check indoor plants for outdoor insects

Q: About a year ago, I received a peace lily. It has done surprisingly well, considering the various opinions I have received on how to keep it healthy.

About a week ago, a caterpillar appeared on the underside of one of the leaves.

Two of the many leaves had been nibbled around the edges, which leads me to believe the pest hadn’t been present for very long. The caterpillar (or whatever it was) was red with black markings.

With this limited information, would you be able to identify this unwelcome visitor and explain how it was able to enter the house and crawl into a large flower pot on a wide window sill?

Also, if this loner was able to find its way into such a succulent meal, might others of its kind follow? There are several other varieties of plants on the window sill but none have been the source of a free meal. Thank you for any help you can be on this important matter. (email)

A: Very likely this particular character did not crawl into your house and find the tempting peace lily to chew on. What probably happened is the female adult form came in as a flying insect (moth, beetle or fly) and laid an egg on the underside of a leaf. The egg hatched and produced this voracious eater. I have no way of knowing what this plant eater was or if you will get more visitations.

Keep an eye on your houseplants for future intruders. Fall is the time when outdoor insects seek shelter against the cold and to perpetuate their species, so many will look for a place to lay eggs to begin the cycle over again for next year. Now would be a good time to check for any spaces in your foundation and to seal around windows and doors.

Q: I have a question about my lilac hedge. Every summer, the leaves turn pale and whitish. Are they lacking fertilizer? (email)

A: This is a powdery mildew that shows up at this time of year. You can prevent this from happening by applying a fungicide for powdery mildew control prior to it showing up. In reality, because it shows up so late in the summer, I recommend just living with it. The plants are not hurt by the infection but are aesthetically compromised.

Q: I think I have night crawlers. They’re worms that come out of the ground and leave dirt mounds in my grass, so it’s hard to mow. What can I use to kill them?

Also, I have yellow spots in my grass. When I lift up the grass, the roots are gone and I see little, white bugs. What do you think they are and how do I kill them? (email)

A: You’ve got a grub problem. I would suggest getting someone to apply a grub insecticide to bring them under control. In doing this, you also will also impact the night crawler population in your lawn by about 25 percent.

Q: Is it too early to trim my peonies down to the ground? (email)

A: As a general rule, yes. The pruning down to the ground ideally is done after a hard frost shuts down any photosynthetic activity in the plants. However, with well-established peonies, this little rule can be ignored with no harm done.

Q: We’ve seen a lot of plants that appear to be wild asparagus. How do we know if it really is asparagus? If not, what is it? I read on a website that wild asparagus should turn a burnt orange in the fall. When is the best time to harvest it? Can it be transplanted to our garden? (email)

A: Wild and domestic asparagus are the same. The plants can be transplanted after a hard frost. You will be able to confirm that the plants are asparagus next spring when the spears start to appear.

Q: We live in southern Manitoba and have 25 trees that we just purchased. We have access to a large water source, but the water is relatively salty. Is this water OK to use for soaking the trees for winter? Our soil is a mix of clay, sand and loam. We haven’t had any rain for a month, so I am concerned the salty water will hurt the trees. (email)

A: You should have the water tested for total salinity and have the salts separated out from the total to determine just what the different salts are. You are correct in being a little concerned about using this water for your trees. I would recommend that you contract to have high-quality water trucked in to use in putting your trees to bed for the winter.

Q: I have a large raspberry patch that is out of control and in need of pruning.

I plan on cutting a path lengthwise to make two rows. I also would like to trim the tops and sides. What do you think of my plan and how much should I cut off at one time? The plants are healthy and produced a lot of berries this year. (email)

A: Go for it. You cannot kill a healthy stand of raspberries. Your plan should make life much easier for you during next year’s harvest. I’ve cut mine down to waist height in the past with no dire consequences.

Q: I have a lawn that is not watered. It has developed two areas where the grass has turned very brown. There also are numerous spots where it looks like a horse has pawed the ground.

Initially, I was told that I had voles and not moles because there are no mole hills. I then was told that I have grubs and that skunks are digging up the grubs and causing the problem. You cannot smell any skunks and no one has seen the skunks or anything else doing the digging. I was thinking I really should water these spots.

What do you think my problem is and what should I do? (McClusky, N.D.)

A: Skunks can roam an area without stinking it up. Their perfume is just a means of defense. A wildlife manager once told me that skunks don’t spray neighborhoods to call attention to them. However, water does miracles for lawns.

If you can or want to, start a regime of watering about 1 to 1.5 inches of water per week to get the lawn to turn green. This will benefit the turfgrass and the roots of the trees that are in your yard.

Q: I was Googling about my dieffenbachia plant and came across your website. I see that you have answered questions for others, so I hope you can answer mine.

We have a dieffenbachia plant that was given to us by a neighbor because it was getting too large for their house. They gave it to us two years ago. The plant is almost 12 feet tall now. We repotted it at the beginning of the summer.

However, it is so large that we had to stake it in the pot. It actually fell over in the middle of the night once because it was not sitting in the pot properly. We since have corrected that problem. How do I stop it from getting any bigger? Can I cut the top part of the plant off? Thanks so much for your help with this because it has been bothering me. (email)

A: You certainly can cut this plant back. In fact, you can cut the cane up into 4 to 6 inch pieces. Lay the pieces sideways in moist, unmilled sphagnum moss. In six to eight weeks, foliar growth will begin emerging from the top of the cut and roots from the base. From one mother plant, several offspring are possible.

If you don’t want to bother with asexual propagation, you can cut the plant back to the height you want and throw the cut piece away.


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.