Trees have stretch marks too!

Have you ever noticed the stretch marks on trees?

Trees grow in height as well as in diameter. Some trees, like the sycamore, allow for the increase in trunk diameter by shedding bark, an all too common occurrence in the spring in my neighborhood.  

Ash, elm and many other trees develop cracks in the bark that run up the trunk.  As new wood and bark is produced under the older outer bark, these cracks allow the tree to expand. 

Cracks also form in the bark when the trunk bends as you can see in the next photo.   

These cracks are normal.

Some Trees are not worth Saving!

This aspen has a canker disease eating away at its trunk.  The disease invaded the tree through a branch stub at least five years ago as can be seen by the annual growth pattern of the damage. 

The fungus feeds during the winter when the tree is at its weakest.  With the onset of Spring, the tree's vigor improves as leaves emerge and photosynthesis begins.  When sugars reach the injured site new callus tissue forms and stops the spread of the fungus. This callus tissue is invaded and killed as soon as the fungus regains control of the tree.  This cycle happens again and again until the tree no longer has the tissue necessary to keep the tree together.  At some point this tree will break at the canker. 

The fungus that causes this problem, known as Black, Target and Ceratocystis canker, is Ceratocystis fimbriata.

Applying nitrogen around the tree after the leaves emerge in the spring will increase tree health.  Two pounds of nitrogen per 1000 square foot area surrounding the tree is the recommended amount to use.  Unless you have had a soil test conducted that shows phosphorus and/or potassium levels are deficient, these nutrients should NOT be applied.  Ammonium sulfate is a good synthetic nitrogen source to use.  Blood meal, cotton seed meal, corn gluten and other organic products are also good nitrogen fertilizers.

Note:  The cat scratches on the trunks are cause for concern. There is a good chance this fungus will be spread to the other trees by the claws of the cat. Removing the infected trunk will help prevent the spread of the fungus.

Poplar twiggall fly causes serious damage.

The poplar twiggall fly is often said to cause little damage to the aspen this insect attacks.

Dead Shoot as a reult of this insect

The vascular damage this insect causes can result in the death of twigs as seen in the photo to the left. 

If these galls are in the main stem of the tree, can the area damged by this insect break off?

An application of imidiclopyrid once a year will take care of this problem.

Note Exit Holes

cucumber sun burn, watermelon sunscald

Charleston Gray and other melons can suffer from sunburn

Watermelon, cucumbers and many other vegetables can be burned by the sun.  This causes white spots on the skin  that extends into the flesh.  This dead flesh may be attacked by saprophytic fungi such as Botrytis and Aspergillus.

While the black spots and smugs caused by fungus are often thought to be the cause of the problem, the intense rays of the sun not providing shade is the problem.

Cucumber with sunburn and a fungus infection.

Covering the fruit with the vines, straw or hay can help prevent this problem.

Maple anthracnose may be due to spring weather.

Anthracnose is the term used to describe a disease that causes limited, sunken dead spots such as those on these maple leaves.  The disease organisms involved vary with the plant but they all require the same environmental conditions, wet and cool spring weather.

This year's spring was ideal for these diseases.  Control is an option that requires frequent sprays from bud break until the weather conditions change.  As soon as warm weather arrives the infection cycle of the disease organism is shut down.

At this time of year there is no reason to spray.  Cleaning up the leaves in the fall may reduce a source of this disease for next year's infection cycle.  

The sprays and spray schedule recommended for Sycamore anthracnose should be followed if you want to prevent anthracnose.  If next spring is warm and dry, there is no reason to spray.

Armenian cucumbers may split open if left on the vine too long.

Jude Sirota provide me a number of cucurbit plants (members of the gourd family) for the Grand Junction Community Garden at the Library earlier this year. One was an Armenian cucumber. This striped Armenian variety is called "Painted Serpent".


You can tell by the one Susan Swift is holding they can become quite long and certainly do resemble a serpent.

If you aren't familiar with this cucumber, they stay tender no matter how long they grow.

The only problem I've had with this cultivar is they split along the stem end. The damage shows up as open sores which enlarge into large splits as seen below.



This problem may be due to too much soil moisture.  Slicing cucumbers tend to become bitter when they lack adequate soil moisture.  Which is worse, a cucumber that is bitter or one that splits open?

Glyphosate damage on ash tree.

This photo of an ash tree shows symptoms of glyphosate uptake. Glyphosate, initially sold as Roundup by Monsanto, is now available in generic form at many farm cooperatives, and retail businesses.  When this product is misapplied it can cause damage.  In this case the owner sprayed glyphosate to control weeds at the base of the tree last year.   These symptoms appeared this year.


Glyphosate may drift onto the buds or be taken in through green tissue at the base of tree . 

Symptoms of glyphosate toxicity the year after glyphosate uptake results in clusters of leaves where shoots should develop.  I've seen these same symptoms on trees in local retail nurseries where the wholesale nursery applied glyphosate to control weeds around the trees the previous year. These symptoms are also occasionally seen on grape vines when glyphosate is used to control weeds at the base of the vines.

Herbicides should be used with care.  Don't assume they are safe.