What Every Homeowner Needs to Know About Their Aging Trees

Where did all the Cankerworms go in the spring of 2019


 Cankerworm Page

March 2009-April 2009

April 30, 2009

I have seen almost no activity this spring.  On my main willow oak band I counted about a dozen cankerworms the entire month of April. I have heard of no other activity this spring although I thought I saw what might be an infestation on Sharon Road near Sharon Lane.  Some trees were late leafing out and that might be due to the fact that they were damaged in earlier seasons and are just a little weaker consequently, later coming out.

Hopefully, this will end our cankerworm problems.  If there are few of them in the spring then there will be no worms to make it through the cycle and lay eggs in the fall.  Remember, we are one of the few areas in the USA where these insects are a major problem. We saw them as inch worms in grade school and yet in the mid 80’s they started being a problem and have been so ever since.  Nature is sometimes unpredictable.  It will be interesting to see what fall brings.

April 20, 2009
There has been much less activity this spring.  I have looked at various trees around town and have seen few worms.  Trees that in the past have had hundreds or even thousands of cankerworms on the trunks or traps have a dozen cankerworms.  We do not need to destroy them all, since most of us have seen these “inch worms” since we were kids.  It will be interesting to see what happens this fall.

April 2, 2009
This afternoon I decided to look at the large willow oak in my front yard.  I have been trapping cankerworms on this tree for many years.  It always surprised me that every year I have a record crop of cankerworms.  Today I found 16 small green cankerworms on the tarpaper trap.  Did these insects blow in, crawl up or crawl down the trunk.  I do not know but they all were caught in the Tanglefoot on the lower part of the trap.  They were each about 1/8th of an inch long.  They might have hatched on the trap itself since eggs are laid their.  They have nothing to feed on so will die.  Last year I saw a similar situation and am sure that those insects hatched on the trap itself because I found egg cases.

I also noticed that many of the city traps were non sticky.  I could place my entire hand on a trap and pull it away with no Tanglefoot stuck to the trap.  That is not the case for all city traps just the ones I tested.  Tomorrow I take the camera out.

April 1, 2009

I was very surprised to day to see my first cankerworm.  It was in an unusual place.  I was working at my office on one of my ponds when I saw a small green worm floating on the water.  The worm was green and about 3/8 of an inch long.  It happened to be under a pecan tree which I do not normally consider one of the prime candidates for cankerworm feeding. 

Anyway, they are here, so prepare your tarps with Tanglefoot..

There was an article in the Charlotte Observer on March 3rd that indicated there was not much homeowner could do except possibly spray small trees such as dogwoods.  The time to act was in the fall.  some parts of town will have heavy infestations and that means thousands of cankerworms looking around for something to eat.  The worms natural inclination is to go skyward and they will climb the sides of your house, telephone poles and of course trees.

If you have that type of attack you can use Bacillus thuringiensis  as a spray to kill the cankerworms that you see on shrubbery or on small understory trees.  But I can assure you that the refreshed Tanglefoot will catch a lot of them going up the tree in the spring.  On a tree in my front yard I captured well over 1000 cankerworm caterpillars a few years ago.  The trap was about to be overwhelmed and I then sprayed the trunk of the tree from the trap down to the ground.  That did the job.

Bottom line ... there are things you can do this time of year to lessen cankerworm problems.

March 25, 2009

Inspect your cankerworm traps and reapply Tanglefoot.

It is time to take a close look at your cankerworm traps.  We had a light infestation in many places this past fall, but there are traps that are full of female cankerworms.  To me that means that there still will be lots of cankerworm caterpillars hatching in your trees and your neighbors trees.  Many cankerworms end up on the ground and will try to crawl upward.  Your trap can catch lots of those insects if their is enough Tanglefoot on the trap.  If you have a plastic Bug Barrier trap you can smear Tanglefoot on the outside of the trap.  You do not have to put up a new trap.  With a Tanglefoot trap refreshing the old Tanglefoot will work.  I recommend starting with a one inch strip of Tanglefoot.  If you need more later you can add more.

Here are a few details about what typically happens in the spring.

In the spring of 2008 about the last of March,  I noticed very small green worms on the black tar paper on the trunk of the willow oak in my front yard.  Upon close examination I realized that they were baby fall cankerworms.  They were about 1/8th of an inch long had hatched from the eggs that were laid on the tar paper.  Typically, the wingless females crawl to the top of the tree and lay their eggs in the upper parts of the tree so they can be near the new foliage when it comes out in the spring.

Because we trap the wingless female insects in the fall, the male is attracted to them by pheromones.  In desperation some of the females mate and lay their eggs on the tar paper.  I have counted as many as 300 eggs in one cluster, but I suspect that the average egg cluster is about 200 eggs.  200 eggs times the number of cankerworms that climb up the tree get to be astronomical numbers quickly.  This year I captured  1,363 female insects.  Potentially, that is 272,600 caterpillars munching away in the top of the tree.

Some years ago, I captured over 5000 female canker worms in one season and a city tree not far away captured in excess of 8000 cankerworms.  Do the math.

Also, by this time of year the sticky stuff on your traps will have dried out, gathered dust, collected leaves, and in general not been capable of capturing the cankerworm caterpillar.  What happens now is that the new young-cankerworms will start feeding on the trees very soon since the willow oak leaves are opening now.  When they have eaten all the tender leaves and buds they will parachute down the tree on silk-like threads or crawl down the trunk.  Those small cankerworm caterpillars that land on the grass or blow in from other trees will have a natural tendency to crawl upward.   They crawl upward by the thousands during a year where there is a  lot of cankerworm activity.  Those cankerworms that crawl down the trunk will get to the ground and crawl to another tree or even a telephone pole and go to the top of that.  No one said they were smart, they are just programed that way.

If you went to the trouble and expense of installing traps take a few minutes to refurbish them.

March 25, 2009

jack mcneary