Tips and tricks against the Tomato Hornworm

Sunday, April 17, 2011

I posted recently about garlic spray, which can be used to control pests as well as disease such as late blight. One pest that I am in search of a good solution for is the tomato hornworm (Manduca quinquemaculata).

Tomato hornworms are closely related to (and sometimes confused with) the tobacco hornworm (Manduca sexta).

One natural control for these pests is the Braconid Wasp, which lays its parasitic eggs on the back of the hornworm. These eggs then eventually kill that hornworm by eating it from the inside out (uhm, yuck)... The moral of the story is, if you see a caterpillar that looks like this, it is a host for an insect that will kill the caterpillar's brethren (not to mention, he's about to be wasp larvae kibble), so you might want to leave him there.

There's a great publication on minimum chemical gardening available from the Virginia Cooperative Extension's website. It includes tips such as tilling, crop rotation, etc... Very good general low-chemical-use information!

I read that you can use naturally occurring Bacillus Thuringiensis (BT) to kill the tomato and tobacco hornworm, and this might be the easiest route. I looked to see if BT is bad for bees (since this will be one of my primary concerns!) and found somewhat mixed information. I don't think I'll be doing much with BT in my garden, especially not in the first year of trying to get my hives established.

For my own garden, I'm going to stick to the "find and pluck (and SMUSH!)" tactic. I've read that the best times to find the hornworms are early morning and evening, they'll be more active on the plant at this time. During the heat of the day they'll hide under the leaves. You can follow their poop (which from what I hear looks like little hand grenades!) or the destruction to try to find them if all else fails.

Good luck with this year's pests, and happy gardening! Let me know if you have any tried-and-true tricks to share!!