Written by Marcia Moffitt
I was wondering why I picked 67 hornworms, Manduca quinquemaculata, on just two tomato plants in the last ten days. I notice that leaves were missing and holes were being chewed into my tomato fruits. This is the first year I have had hornworm problems on my tomato plants. Joy Paterson and I discussed this and I described what was planted next to my tomatoes this year.
My vegetable garden is under renovation, so I am gardening in containers in a new location. The realization came that it might not be a good idea to place my tomato plants near my butterfly bush. Why? Because I had created the perfect environment for the hummingbird or hawk moths to complete their entire life cycle within a five foot area. The adult moths were attracted to my butterfly bushes. Hornworm adults are diurnal, with peak activity times at dusk and dawn. Mating occurred and female moths had a very convenient habitat for laying eggs with my tomato plants just feet away. Each morning and evening the females were passing by and laying more eggs. I had multiple generations with larvae of various sizes on both of my plants. They were happily munching on the fruit and leaves of my tomato plants. Look for round holes in the fruit, large round “bites” out of leaves, or dark green clumps of frass (insect feces) to see if hornworms are feeding. If you notice damage, look closely at stems and in the soil around the the base of the plant. Searching at night with a flashlight will also catch them in the act of feeding.
The fact sheet Tomato and Tobacco Hornworms is a great resource on the life cycle of this particular pest and control methods. More information on the damaged caused can be found at Grow Your Own Nevada’s web page on hornworms. These sites provide a good description of what I experienced as the damage was quick and severe to both the plant and fruit. Since they were detracting from my production, I decided to recycle and feed them to my laying hens that scarfed them up as a tasty treat. Squishing them is also an effective way to remove the larva, if you do not have chickens.
If you find these larva, you can also rear them out as a science experiment. The Manduca Project has some great suggestions for rearing them through to adults. Though after the devastation I experienced, I cannot imagine myself rearing these critters despite the beauty of the moth.