NDSU Extension Service - Ramsey County

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May 3, 2010 Horticulture Column

Howdy!!!

Well, time has come for us to realize that spring can take a drastic change.  The weather sounds as if the winter season might come upon us again, only without snow I think.  It was really interesting to watch landscapers and homeowners think about their landscape design and the need to fall for the teasing weather we have had.  I have talked to many people that have bought flowers and even tomatoes and thought they should have them planted.  Well, I have talked about the average frost date in our area for many years now and still need to remind all of you that our average date, for frost, is May 20th.  That means we have experienced frost into the month of June and of course a month prior to May, as well. 

We still have several issues to deal with and the fact that many of trees were fooled into budding and starting to flower.  In the next couple of weeks we may lose those beautiful flowers and thus have a very reduced apple, June berry, plum or even pear production.  So, if we have trees that don’t seem to bear much fruit remember what happened this spring.  Well, I got off on a tangent and was really meaning to talk about our spruce trees.

With the onset of spring our spruce trees become very beautiful.  They seem to take on a new green life of their own.  I won’t be long before the new buds open and the old caps start falling off.  This is generally the time of year we need to pay attention to the dreaded fungus Rhizosphaera needlecast.  If our weather would have stayed warm and dry the need would have been much less but now that our weather has turned cool and damp, we need to think about protecting those new needles for the upcoming season.  For many years homeowners and landscapers have been protecting the new buds with a product containing Chlorothalonil.  This is a fungicide and does a pretty good job of protecting not only spruce tree needles but also other plant materials to include tree leaves and vegetables, like tomatoes.  The label would say to make a needle cast application (after all of the new bud caps have fallen off) and another application two weeks later.  I argue with that logic and say that the first application needs to be much sooner as the new bud caps do not fall off all at once.  My recommendation would be to make the first application when approximately half of the caps have fallen from the new buds and the second application two weeks later or when the remainder of the caps have fallen off of the tree.  My reason for suggesting the earlier application is the new needles are the most prone for infection and by waiting for all of the new caps to fall will have allowed the older new needles to have been exposed and started their hardening process.  We need to attack this fungus earlier not later.

 

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