Category Archives: Horn Worms

control hornworms with Bacillus Thuricide

Controlling hornworms on tomato plants

Any gardener who has grown tomatoes know how destructive the horn worm can be in your tomatoes.  If not caught in time these little green eating monsters can destroy your tomato crop. Fortunately if you find them early they are easy to control.

We weren’t in the garden for about 4 days and I missed the signs of horn worms until they had done some serious damage.  We went through our plants and plucked off any horn worm caterpillars we spotted.

When you spot hornworms

As soon as you see them, or their droppings, examine your plants and remove any of the caterpillars you can find.  Dispose of them accordingly.  They blend in amazingly well and several are going to be missed.  Any missed will be controlled with the BT

hornworm caterpillars
hornworm caterpillars

Bacillus Thuricide to control hornworms

The name may sound intimidating, but BT is actually a bacteria and is absolutely organic.  Gardening stores will often carry it or you can get it from Amazon.

Bacillus Thuricide kills hornworms
Use BT, Bacillus Thuricide to control hornworms and other caterpillars

We like to mix up a gallon of it at a time in an inexpensive little sprayer like in this picture below.  It cost us about $12 and is on its third season.

As a slight aside, I would recommend writing the contents of the sprayer on its side with a good permanent marker.  We also have a dedicated set of cheap kitchen measuring devices dedicated to just our garden.

Apply bacillus thuricide with this sprayer to control hornworms
Chapin 20000 Poly sprayer we use to spray for hornworms

After the BT is mixed according to the instructions bottle simply apply a heavy mist to all the leaves on your tomatoes.  The caterpillar will eat the leaf, ingest the BT, and will die within 24 hours.  Generally I find them hanging dead the next morning.

In this picture below you see one of the large hornworms I missed when picking them by hand.  Often times you will also see them hanging after they have turned a dark brown color.  You can leave them or toss them into the yard.

hornworm killed with BT
hornworm killed with BT

You can be proactive

Instead of waiting until you see these destructive caterpillars to apply BT you can head them off at the pass.  Weekly I try and apply BT to all our plants.  While utilizing this defensive measure in our tomatoes the hornworms just don’t survive long enough after hatching to do much damage.

Video on using BT

Towards the end of this video you can see what their frass looks like.  You will find it at the base of the plants and is an indication that you’ve got tomatoes being destroyed by this insect.