April 11, 2002

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I believe that our potatoes last year suffered from blight. They were growing well when I noticed a few spot on the leaves. Following a rain, they lay flat and died. We did get some potatoes, although not the usual amount, and the flavor, especially of the skin, was not good. They didn’t keep well either. Is it blight? Can it be treated when it is first seen? We had planted new Norland seed 4 to 6 feet from where we had grown potatoes before. (Pierre, S.D.)

A: You need desperately to practice crop rotation with anything but members of the potato family, like tomatoes, eggplant, and peppers. Potatoes and their family members should stay out of the same site for a minimum of three years. This is the first and most important step in disease control.

Q: I am concerned about our blue spruce evergreens. They are up to 25 feet tall, but we are starting to lose some of them. They are dying from the top down. The needles turn brown, then die, about a quarter of the tree at a time. The trees are not all in the same place in our yard. We have tried spraying the trees and also water spraying, none of which seemed to help. Any help that you can give us would be greatly appreciated. (New England, N.D.)

A: Usually a top-down death of spruce is more likely to be an insect-related problem than a disease or environmental problem. I suggest cutting the affected trees back to the second or third whorl of healthy branches and examine what you remove carefully. It could be damage from either the spruce budworm or the yellowheaded spruce sawfly. I suspect the latter. Or there could be a borer that is causing the damage. Rather than guessing, I suggest sending a sample of the damaged area along with some of the unaffected plant to either me or Cheryl Biller of NDSU’s plant diagnostic clinic. That way we can more accurately advise you on a course of action.

Q: I just read your column and noticed that someone is looking for Sheyenne tomatoes. We grow them where I work (at Harmens Greenhouse near LaMoure). We save the seeds each year and have a large demand for them. We wholesale as well as retail, so your inquirer may find them at a location near them. I'm sure if they contact Harmsens (701-883-5813) they would be glad to let them know of a source nearby. (LaMoure, N.D.)

A: You have no idea how happy you made many people in our area! Thanks for providing the lead.

Q: I have 3-year-old raspberries that barely set fruit but did not develop beyond that stage. I have just been cutting out dead stalks in the past but now one of my garden catalogs says to cut Heritage variety back to the ground each year. (Napoleon, N.D.)

A: Yes, cut Heritage back every year, right to the ground.

Q: Can systemic anti-fungal treatment be used for needlecast? If so, what are the products that can be used? (Campbell, Minn.)

A: Unfortunately, there are no systemic fungicides labeled for needlecast. Only chlorothalonil and Bordeaux mixture, which must be applied for two consecutive years, shortly after the new needles have elongated.

Q: I have a client in here who's wondering how deep a root system a 50-foot evergreen tree has. He's wondering if they blow over easy. They haven't blown over yet through some pretty tough winds. A garage is about 20 feet away. (Linton, N.D.)

A: I cannot quantify the root mass for any particular tree for you. All I can tell you that it is extensive if the tree is healthy and the soil conditions are not adverse. Neither can I guarantee that the tree will not blow over in any future winds, even though it has survived severe winds to date. Evergreens become more prone to windfall because of the "sail effect" they present to the winds with their perpetual foliage cover, and when a high wind storm has been preceded with a soaking rain that may soften the soil enough to loosen the root system's anchoring function.

My advice: if the client feels at all leery about the tree falling on anything of value, he should have it removed.

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. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu