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Tree Pests

Here are the three most recent studies we’ve done:


The Codling Moth

We have an old apple tree out by our garage that keeps trying to give us apples.  Since we usually neglect doing our part to combat the pests, however,  they end up rotting on the ground,  unfit to eat because of how wormy they are.  I found the Handbook of Nature Study‘s section on the codling moth and its effect on apple trees, and thought it would be just the thing for us to study up on.

We learned that the moth lays her eggs on apple tree leaves, and when the eggs hatch into caterpillars, these little villains find their way to the blossoms just after they have dropped their petals, but before the calyx has closed completely.  They burrow into the developing fruit and hide out inside the apple right next to the core, feeding on the sweet pulp of the fruit until it’s time for them to pupate.  They leave the apple by way of a tunnel they burrow for themselves, find a loose piece of bark to tuck themselves under, and spin their cocoon.  They overwinter in this form and become adult moths in the spring.



The spot around the core where the caterpillar must have been.




Allison’s and Megan’s journal entries, ages 12 and 9.

So, in order to prevent wormy apples, it’s necessary to spray right after the petals have fallen, and right before the calyx closes.  We also learned that nuthatches, chickadees, and woodpeckers feed upon codling moth caterpillars while in their cocoons during the winter. 

The Fall Web Worm

This pest doesn’t cause as much damage to trees as the codling moth.  The biggest problem with these caterpillars is that they are unsightly.  Only if they are found in great numbers in a tree might they weaken it eventually.  I know I’ve seen fall web worms in trees along roadsides and in fence rows, but after studying it in detail, and knowing exactly what their web looks like, I have yet to find one this fall.

My journal entry.

The biggest thing we learned is that the fall web worm is distinct from the tent caterpillar.  Tent caterpillars make their nest in the spring in the forks of the branches, crawling around the outside of the nest and leaving it in order to feed upon the leaves of the tree.  The web worm, on the other hand, builds it’s nest at the tips of branches right around the leaves.  They remain inside the nest feeding on the leaves it encases. 

The Acorn Weevil

I knew we’d have plenty of opportunity to observe the effects of this pest on oak trees.  We occasionally take walks through a woods where acorns are scattered all around the path.  I used Stokes Guide to Observing Insect Lives to read up on this insect.  




Logan’s and Jeff’s journal entries, ages 10 & 6.

We’ll probably never get to see the adult insect itself (only 1/4 inch in length) unless we become daring tree climbers and prowl around in the tree tops of oaks during the summer, because that is when the weevil is active, laying her eggs on the acorns.  It is after the acorn falls that the caterpillar inside tunnels its way out  to burrow underground where it will pupate for the winter.  So if you find an acorn that’s kind of squishy, but has no exit hole, there’s a good chance you’ll find a creepy crawly inside.  If it has legs, its an acorn weevil larva.  If it doesn’t, it is some other kind of worm that also feeds upon acorns.  If you find an acorn with a hole the size of a pinhead, then you’ll know that a caterpillar has been inside, has eaten the meat of the acorn almost entirely, and has already exited.

That wraps up our study of tree pests.  Allison was relieved when I announced that our next topic for nature study was ladybugs.  She said she was tired of always studying the bad bugs!

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8 thoughts on “Tree Pests

  1. Wow, an acorn weevil huh? Thank you so much for the details about this pest. I'm going to share this entry with my son and I know we will be on the lookout. Also, LOVE your children's journal entries!

  2. After my daughters brought a whole bunch of acorns into the house for their collection, we ended up with all sorts of creepy, crawling little maggots falling out of the cabinet. (Um, yuck.) I didn't see any of the pin holes, but perhaps they were a different bug in the acorns. (They looked like little white worms, with very hard to squish bodies.)I love learning about bugs. Bugs are simply my FAVORITE nature study item. I wish we had handled our tree study as a platform to study bugs. The differences between fall web worms and tent caterpillars was simply fascinating to me. I never knew that. Now I want to go find some fall web worms and examine their nests. 🙂 Great study.

  3. Great study! A few of the acorns that we were identifying had a telltale pinhole in them! (www.garnergoingson.wordpress.com)FYI I have had three or four (lost count)attempts at this comment 😉

  4. Wow! This was fantastic and really interesting. I've seen those holes in the acorns and learned the hard way not to bring a bunch of acorns inside for an extended period (little wormy things crawling around).Thanks for sharing and great job on the journal pages!Sarah

  5. Bad bugs…..made me laugh. Yah for ladybugs!This is a wonderful entry showing your tree/pest studies and your journals are fabulous. I learned a lot about the coddling moth and how it affects the apple development. Thanks for sharing your study with the OHC.

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