Thursday, April 16, 2009

What to do about Tent Caterpillars

You've seen them. In your cherry trees. If you haven't yet then take a look, they are on their way. Tent Caterpillars can be devastating to the foliage of young trees especially those of the prunus genus. They may look all cute and cuddly up close but when allowed to let loose they feast like there is no tomorrow upon the lovely new leaves of your trees.


Tent caterpillars overwinter in groups of 150 to 400 eggs and hatch hungry in the spring. They join together as a community of pests and create white, silky, sticky nests to serve as their base of operations. If you can reach their base you can easily take them out but the task becomes more difficult the higher in the tree canopy they occupy.

These particular caterpillars were in my in-laws plum tree. A stick was all that was needed for their removal.
I mentioned how to treat tent caterpillars last year and here's what I said:
According to the University of Kentucky Entomology Department you can treat them with insecticides that contain Bacillus thuringiensis var kurstaki. You could also use insecticides with carbaryl, methoxychlor, and malathion.

One method they recommend is to take a large stick poke the nest and twist. Most of the nest should pull apart and wind up on your stick like cotton candy! Other than that prevention is the best method. Take the eggs off the trees during the winter months or remove the nests as soon as you spot them.
I've also found that a spray with dish detergent and water will work well for those nests that are easy to reach. If you have an extremely large tree that they are nesting in you probably don't have to worry about the health of the tree too much. The tree should be able to recover from the defoliation but those nests don't look very nice. I would still be tempted to break them open and invite the birds for a snack.


After they have gorged themselves on your trees they will wander away to form cocoons and enter their next stage of existence. They won't do any further damage to your trees at this point so if you see a wandering worm don't worry, they are just going to become moths and hatch the next generation!

This Caterpillar Killer concentrate from Safer contains BT (Bacillus thuringiensis) which is an organic pesticide effective against Caterpillars.

8 comments :

  1. Sigh. We know tent caterpillars, all right. Unless they're on our fruit trees, we generally hope the birds will deal with them. But it's amazing how they'll even set up shop in our black walnut trees! Grrrr.

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  2. We've had them in our Shagbark Hickory and Oak trees, also. Unfortunately they are so high in the air, I couldn't possibly spray them. But, thankfully, there aren't that many of them. Thanks for the information, though. Should they be in reach... watch out! ;-)

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  3. I just hate these guys. I have a wild cherry tree that they like. It is a pain but too far up for me to reach. I just let it be. I wish there could be resistant trees to it as all those prunus species are so susceptible. Thanks for the info! Dish soap is good stuff.

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  4. They are unsightly. I had some in a walnut tree and before we could get them out some dropped by birds I guess into areas below causing more damage. Yuck. Thanks for the tips.

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  5. We have those ugly looking tents in some of our trees too!

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  6. Looking at those things gives me the shivers almost as bad as touching slugs! Luckily we don't have too much of a problem with them here.

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  7. This is the UGH part of spring.

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  8. Haven't noticed any around here yet. But I'm sure I will soon enough.

    (Where might I find the "Garden Pictures Taken With..." widget? Thanks.)

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