If you discover a tomato hornworm caterpillar in your balcony container garden, prepare yourself for a nightmare. If you notice damage on your plants, especially tomato plant leaves, search closely for a green, leafy-looking caterpillar.
If you find one, kill it on the spot and immediately search for more caterpillars. These caterpillars may find their way onto your balcony and ravage your container garden, and you wouldn't believe how fast they will consume the leaves off your tomato and potato plants.
You can see in this picture how you can miss even a huge caterpillar on your plants - it looks exactly like a plant leaf, even clinging on to the bottom of a stem to camouflage itself. You will often find these caterpillars as very tiny half-inch specimens, but the monster garden pest pictured here had grown to 4 inches long.
To kill a tomato hornworm caterpillar, you are supposed to cut it in half, but not many gardeners want to do this. Pluck it off the container plant and spray it with raid. It will leave cocoons even inside your plant containers, so pluck them out and spray these cocoons with raid, as well. Be careful to not spray your plants. It is best to get an insecticide that is safe with plants, although even most plant-safe insecticides are not supposed to be used on edible plants in kitchen gardens. This is why you should spray the caterpillar on the floor away from any edible container plants.
The tomato hornworm caterpillar (Manduca quinquemaculata) will turn into the five-spotted hawkmoth. These caterpillars can be found on tomatoes, potatoes, eggplant, moon flowers and tobacco plants. They and many other garden pests are repelled by the odor of the marigold flower. These caterpillars overwinter in soil burrows, so you may find cocoons on the inside of your plant containers. If you have a problem with tomato hornworm caterpillars but also have wasps around, keep the wasps. Wasp larvae parasitize these caterpillars and kill them. The best way to keep them out of your garden is to plant marigold flowers around their plants of choice.