For Release November 17, 1998
Unnecessary Pine Panic
by Chuck Otte, County Extension Agent
I really didn't mean to start a case of community pine panic with last weeks column about pine wilt, but it appears that I did! Subsequently I've gotten to look at a lot of pine trees the past several days. Let's follow up last weeks column with additional information about pine trees, diseases of pine trees and environmental problems of pine trees.
First of all, not all evergreens are pines. There are also a lot of cedars (junipers) and spruce trees out there and even a few fir trees. The pine wilt that I talked about last week is very specific to pine trees and specifically the Scots or Scotch Pine. (Everyone calls them Scotch Pine but to be correct they are Scots Pine!) Not just with this disease, but just for general management it is very helpful and important to know what kind of trees and shrubs you have in your yard!
We do have a lot of blue spruce trees in this town. I do not recommend trying to grow blue spruce because they have a lot of problems. They do not have diseases, they will occasionally be troubled by bagworms or spider mites, but the big problem with blue spruces is the weather, the climate and the soils. Save us all a lot of headaches and don't plant blue spruce!
Just because pine trees are called evergreens does not mean that they keep their needles forever. Most pine trees will only hold needles for 2 to 4 years. After that time the inner older needles usually become so shaded that it takes more energy to keep those needles alive than they produce through photosynthesis. Therefore they are excess baggage and the tree gets rid of them. We are seeing a lot of routine needle shedding right now. These needles usually turn yellow, sometimes bright yellow, and then they fall off the tree. You will not find needles being shed clear to the end of the branches. This is a big difference from pine wilt where the needles turn brown and then stay on the tree for 6 to 12 months. Needle drop will occur on any species of pine tree. When a Scots pine has pine wilt ALL the needles turn brown and it will happen very quickly and uniformly throughout the tree. And remember that it is only likely to be seen on Scots Pines.
There are other diseases and environmental conditions that will cause pines to develop brown needles. Austrian pines, especially older Austrian pines, will develop Sphaeropsis tip blight. This disease attacks the new growth tips and kills them, often leading to a long lingering death of the tree. This disease is curable with fungicides. Austrian pines can also develop Dothistroma needle blight. This disease attacks the older needles causing banding and slow death of the needles. Again this disease can cause slow death of a tree, but is curable with fungicides. Brown spot is a disease of Scots pines primarily. It is a relatively slow moving disease that kills needles and can kill a tree over many years if untreated. All of these diseases are slow moving unlike the rapid death of pine wilt.
Often times well also get heat scorch or cold scorch on our pine trees. In most cases this condition causes needles to turn brown, from the tip of the needle inward, looking just like youd held a blow torch to the tree. This is normally seen on just one side of a tree, often the south side. Pine trees do not like wet feet. Ive seen several pine trees die this year from saturated soils. It is fairly easy to determine if this is the cause by site analysis. These trees usually turn uniformly off green. This can be on any pine species and the needles dont show the rapid browning color of a pine wilt infected tree.
I hope this has helped separate some of the afflictions that can affect pine trees. We have a lot of pine trees in this community. Homeowners are quite fond of their pine trees and another epidemic like Dutch Elm disease is certainly concern. But lets make sure we know what weve got before we start to panic!
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