[Arid_gardener] control of tomato horn worms

[Janet Howe]

Wow Glenn, I'm impressed with your tomatoes!  I'm glad my suggestions helped you last year.  I got my tomatoes into the ground a little late this year, they aren't anywhere near the size yours are yet.  What types did you plant?  I seem to have the best luck with a type of "grape" tomato a lady in Las Vegas has developed - last year they were the size of large Romas and tasted wonderful.  

So, in answer to your question, I too have experienced those lovely "little" hornworms.  I'm not a fan of pesticides, so I've never used anything other than picking them off the plants when I see them and looking for and discarding the larvae sacks (they look like 2-3" little brown cigars with a tail that folds back over on itself) as I turn the soil in the spring.  When I first encountered them it was quite a shock, they're really pretty weird looking. 

As far as taking care of your current plants, you learned the same lesson I did, that you have to keep a daily watch on the plants for signs of them, and then get rid of the worms that you find ASAP.  However, I did a search on the internet, and here's a short synopsis of what I found:

Hornworms are often difficult to see because of their protective coloring. Not much for the heat of direct sunlight, they tend to feed on the interior of the plant during the day and are more easily spotted when they move to the outside of the plant at dawn and dusk

CONTROL: 
* Handpicking. The large size of hornworms makes it easy to get hold of them. Once removed from the plant, they can be destroyed by snipping them in half with shears or dropping them into a bucket of water. (by the way, they don't bite!)
* Rototilling. Turning up the soil after harvest will destroy any pupae that may be there. 
* Biological. Bacillus thuringensis, or BT (e.g., Dipel, Thuricide), is also considered very effective, especially on smaller larvae. Spray it as a precaution. Natural enemies, such as the parasitic wasp that lays its eggs on the hornworm's back, are common.  If found, such worms should be left in the garden so the emerging wasps can parasitize other hornworms. 

Parasitic wasp cocoons on hornworm
* Insecticides. Hornworms can be controlled with carbaryl, permethrin, spinosad insecticides. Read the label carefully before using any insecticide. 

Here are some links that you might find helpful, and they include some good pictures that will help you find them on your plants. 

http://cals.arizona.edu/pubs/garden/mg/entomology/garden.html

http://www.coopext.colostate.edu/4DMG/Pests/tomato.htm

http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/hornworm.htm

http://www.ehow.com/how_9366_control-tomato-hornworms.html



Good luck with your plants!

Janet Howe
Master Gardner volunteer


________________________________________
From: GKKlassen & Family [mailto:gkklassen at cox.net] 
Sent: Sunday, May 07, 2006 7:18 AM
To: Janet Howe
Subject: Help with my tomatoes!

Dear Janet,

	Last year you helped me with "blossom end rot."  Your advice worked perfectly. Thank you!

	This year I moved my tomatoes to a raised bed I constructed using 1 x 12's, then filled it with compost, manure and good topsoil.  I purchased a timer for my soaker hose and give them plenty of water and fertilizer.  The attached photo shows my tomatoes now in the ground since March 22nd.  I planted four varieties.

	Last year I went totally organic, no pesticides whatsoever. I did use ladybugs to attack some aphids early in the season.  However, I neglected my plants for a couple of days and when I finally looked in on them, those huge "horn caterpillars" had completely devastated my crop. The entire top two feet of each plant was completely stripped of all foliage.  There went my September and October tomato harvest. I was very disappointed. 

	Well this year I'm going to "nuke" 'em.  Any advice on what pesticide I should use that has the least negative impact on the environment?

Sincerely,

Glenn Klassen
380 West Aloe Place 
Chandler, AZ 85248-4504