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Past Articles Library | Trees | Pests of Dogwoods

Dogwoods are a wonderful addition to any landscape plan.  They are referred to as an understory tree.  What is an understory tree?  Well, it is a tree that can survive under another tree or from the shadow of it.  If you are not really sure what I mean, take a look at where wild dogwoods are growing.

Dogwoods love a soil that is rich and moist.  They do not like to stand in water though so pick a location that is shady while having a soil that is nutrient rich and well draining.

When it comes to planting a dogwood, do not be tempted to harvest one from the wild, which has a good potential of caring plant diseases and pests.  Instead, purchase one from a plant nursery.

Once you get it home, the next step beyond site selection is to prepare the hole.  The dogwood tree should never be planted any deeper than the container it came in.  The width of the hole needs to be twice to three times larger than the container.  While you are digging your hole, do not just throw the soil on the ground.  Place it in a container so that you can mix in good amount of well-seasoned compost, which will help make the soil more nutritious for the tree.

After the hole is dug, the next step is to remove the tree from its container.  The easiest way to do this is to cut the container away from the root mass.  The next step is an optional one but is very important if you have clayey soils.  To allow the roots of the tree to grow outward, you will need to deglaze the hole.  This is not a complicated process and only requires one to take a rake and rough up the inside of the hole.  Once that is done, run your fingers through the roots and then place the tree in the hole. Stir up the soil and compost mixture and fill in the hole.  Water the tree in to settle the soil and add more soil as needed.  Next place mulch on top.

Cercospora and Septoria Leaf Spots

These two leaf spot plant diseases are caused by two different types of fungus.  While this plant disease will not kill the tree, it will make it look unsightly.  How do you know if you have either one of these leaf spots?  Well, take a look at the leaves.  The spots will either be brown or dark brown to red in color.  The location of the spots is very important when it comes to diagnosing the problem.  Both of these leaf spots will locate themselves between the leaf vines.

If the fungus problem is bad enough, the effected leaf will drop off prematurely. 

The best way of prevention and control is to keep the garden space clean.  What this means is to rake up the leaves throughout the season.  If you think you may have this plant disease on your dogwoods, throw the leaves in the trash.

Dogwood Anthracnose

This is another plant disease caused by a fungus.  While many of the funguses that attack the dogwood only affect its appearance, the dogwood anthracnose is different.  It can kill the tree. 

The symptoms of this plant disease start in the early spring.  You will begin to see leaves that have tan spots with purple edges.  This will begin on the lowest branches of the tree.  As the season progresses, more and more leaves going up the tree will be effected.  This fungus will continue to go up the tree and will eventually start to grow on the shoots, branches, and finally the truck.  The appearance of this disease on the woody part of the plant will appear as brown, sunken areas or cankers.  As the canker grows or several cankers come together, the wooden area the canker is on will die. 

The first line of defense when it comes to this plant disease is to only plant dogwoods that are dogwood anthracnose resistant.  The second approach is to keep ahead of the disease.  What I mean by this is to remove leaves, twigs, stems, and branches that are affected with this disease.  When utilizing this approach, make sure that your pruning equipment is clean before each cut.  This will reduce the chances of spreading the disease.  How do you sterilize your equipment?  Well, it is very easy and only requires you to wipe down the cutting surface with rubbing alcohol or bleach before every cut.

Next, make sure to rake up all the leaves as they fall.  To keep from spreading the disease, do not compost.    

Spot Anthracnose

As in the other anthracnose, this plant disease is caused by a fungus.  But unlike other plant diseases of the dogwood, spot anthracnose attacks the flower bracts first.

As far as the treatment goes, follow the recommendations for dogwood anthracnose.

Powdery Mildew

Powdery mildew is caused by a fungus that likes it warm and dry during the day and cool and damp at night.  Unfortunately, this is the type of environment that dogwoods like but not all is lost.  The first step in controlling this plant disease is identifying it.  Powdery mildew looks like a fine powder that can be found on the tops of leaves.  This fungus can give the leaves a scorched appearance around the edges along with yellowing of the leaves.  As the disease progresses, the diseased leaves will fall off prematurely.

Control of this plant disease can be a little bit of a challenge since it is spread by wind but there are a few things one can do to reduce the chances of developing this problem.

The first thing to do is to keep the garden space clean.  What this means is that you should rake up all the leaves and destroy them.  While leaves can be a great mulch and/or compost, if you think you may have a powdery mildew problem, do not save.  Keeping the leaves around will compound the problem with powdery mildew the following garden season.

The next thing to do is to address the environment that the dogwood is in.   What this means is to open up the space so that more air and sunlight can penetrate.  This can be a challenge because you want to remove enough to increase air circulation while keeping enough available foliage to keep it shady.   In doing so, the best approach is to remove plant material that is crowding the space along with overwhelming branches.

When in doubt, the best approach is to plant dogwood varieties that are powdery mildew resistant.

While dogwoods can have a few problems, they are well worth the effort and will reward you with a display that lasts three seasons.

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Rotate Certain Crops

Avoid planting potatoes and tomatoes where they grew last year. They carry the same diseases, so it's best to rotate them.

You'll have much healthier plants, and more successful crops.

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