Saturday, August 5

Bad Bug/Good Bug part II


I finally started digging in the mowing edge today, and was working around the tomato plants when I found it: A tobacco hornworm. Tobacco and tomato hornworms eventually become cool-looking hawk and sphinx moths, but at this stage of their lives they will decimate your tomatoes, peppers, tobacco, and eggplants.

My first inclination was to take him over to the driveway and squish him. I wasn't quite sure what was up with the little cottony hangers-on, though, so I decided to come inside and do some internet research to figure out whether this was a normal sight or whether I had yet another pest to deal with in the garden.

I'm glad I did my homework, because the little white things are the cocoons of small braconid wasps, a.k.a. parasitic wasps--in this case, most likely Cotesia Congregata since since hornworms are their favorite hosts. These parasitic wasps lay their eggs inside the skin of a young hornworm larvae. Their babies feed on the insides of the hornworm until they pupate into the cocoons you see above.

Once they emerge from their cocoons the new adult wasps will fly off to find mates and start the parasitization cycle all over again. The hornworms do not survive the raising of these parasitic wasps, so it's best to leave hornworms in the garden if they have cocoons attached. In effect, the hornworm is already doomed and by leaving the cocoons to hatch you will be raising some beneficial insects to help you fight future garden pests.

I don't know what's up with me finding all of these bad bug/good bug combos this week, by the way. But I'm sure getting good use out of one of my favorite books for garden bug identification: Garden Insects of North America by Whitney Cranshaw.

10 comments:

Nutbuk Ug Bulpin said...

Such an interesting infos between the bad bug and the good bug!

steven said...

I'd like some of those wasps myself.

Blackswamp_Girl said...

nutbuk, I agree--it's so interesting to see how all of these creatures relate to each other in the garden!

steven, I'd be glad to send you some cocoons. The price is just a pound of your delicious San Marzanos... *wink*

Carol said...

I've been having close encounters of the insect kind, too. Must be the season for them.

Claire Splan said...

Seems like this is an indication that you've got a good ecosystem going. It's great when you can sit back a bit and just let nature take care of itself.

steven said...

nuh-uh, ain't gonna happen. :-P

Blackswamp_Girl said...

Claire, I hope so--I'm sure I'll have to intervene somewhere at some point, but I'd be happy if my "work" that way is minimal!

Steven... lol... I figured as much! It's always worth a try, though, right?!?! ;)

Kati said...

Kim, great post on one of my biggest fears: running into one of those monsters in the tomatoes! I planted lovage partly because I read somewhere that the adult wasps feed on the flowers.

Nelumbo said...

That's a really neat story and picture to go along with it!

Nelumbo said...

That's a really neat story and picture to go along with it!

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