Sunday, 22 July 2012

Tomato Hornworm Infestation

Two evenings ago I noticed the tell-tale signs of tomato hornworms on my tomato plants.  The most obvious sign was that some of the branches were stripped of their leaves which stood out because I visit my garden everyday.  Closer examination also revealed a few small tomatoes that were munched on.  Hornworms are a serious predator that cannot be ignored as they will do a lot of damage to the plants in a short period of time.  We haven't had an infestation like this for three years.

The hornworms are huge and thick (up to 4 inches long and 1/2 inch thick).  They can be tough to see because they have the same green colour as the tomato plants.  Friday evening I picked off about sixteen and a further half dozen on Saturday morning.  I use gloves when picking them off because they often excrete a green fluid as well .... just gross.

The most effective way to get rid of them is to pick them off.  You can find them by closely searching the damaged areas of the plant.  They like to hang upside-down on branches and leave small clumps of feces on leaves.  I also noticed that they sometimes make a clicking sound (not sure why)....which led me to more than a couple of them.  I will also check my pepper plants tomorrow.
Tomato branch eaten by a hornworm.  In the lower right corner of the photo you can see the guilty insect.


Feces from a tomato hornworm.

Friday night's harvest.


  1. Hi Mike! My parents, who live southwest of Ottawa, are dealing with a tomato hornworm infestation as well. This is the first year they've ever found more than one or two worms in the garden - to date this season they've found over 35. I wonder why the upsurge? Perhaps the mild winter is to blame?

    1. Hello.

      From what I've read, the hornworms hatch from eggs layed by giant moths. I have seen these moths in the past and they are impressively large. I suspect the spring and summer conditions we experienced had more to do with it than the mild winter because the hornworms/pupae/moths are very common throughout cold regions of Canada and the US. But ever since my infestation 3 years ago I've always kept an eye out for the damage and pounce on the buggers as soon as possible. One day makes a big difference.

      When I rototilled in the spring I came across many reddish brown cocoons (pupae) of the moth in the soil. They looked a little smaller than this picture I tossed them out of the garden. But I doubt you can get them all causing the cycle to continue.

      For the record I picked out 26. One of my neighbours picked +20 and another said they picked "lots". I know for a fact there are at least two more that I just can't find.

      Thanks for the comment and good luck to your parents.


    2. Hi Mike,
      I was at my sister in law's house last weekend and she mentionned something about huge green worms eating her tomato plants. So we went to check out the garden and there it was! Just sitting there eating a leaf! She had picked several off the day before. Seems like they are quite abundant this year as this was the first time I had ever seen one (or heard of them). Good thing I read this post a few days before... It really made me look like I knew what I was talking about!