The Tomato Hornworm: How to Identify and Control It
Tomato hornworm (Manduca quinquemaculata) is a tomato pest with a big appetite! If left unchecked, it can consume a single tomato plant in just a couple of days.
It’s regularly confused with the tobacco hornworm (Manduca sexta), which is strikingly similar.
Both feed on members of the Solanaceae (nightshade family) such as tobacco, eggplant, peppers, potatoes … and of course tomatoes.
In fact, the tomato hornworm and the tobacco hornworm are often referred to interchangeably since they look alike and inflict the same kind of damage to your tomatoes. They have even been found on the same plants! Both are identified by their characteristic horn on one end (although each’s horn is a different color).
Whichever hornworm you find in your garden does not really make a difference. The main idea is to eliminate the pest so it won’t gobble up your tomatoes and plants.
What do the tomato hornworm and the tobacco hornworm look like?
Tomato Hornworm P. Choate, University of Florida
Shape: cylindrical; caterpillar-shaped
Color: green, which allows them to blend in with the tomato plant
Horn: tomato hornworm – dark blue, dark green or black; tobacco hornworm – red
Markings: tomato hornworm – eight, V-shaped white or yellowish strips across the torso tobacco hornworms – seven, straight or diagonal white strips edged with black across the torso
Size: both can grow to be 3-4 inches long
What do the tomato hornworm and the tobacco hornworm do to plants?
They attach themselves to the underside of a tomato’s leaves, making it difficult to find them right away. You may first recognize the hornworm’s damage at the top of a plant before you find the pest itself.
They feast on both tomato leaves and green tomatoes. Look for –
stems missing leaves
dark green or black pellet droppings (also called frass) on a lower leaf indicating the presence of a hornworm above
When do they do their work?
Both hornworms avoid the heat. They stay in the interior, shaded part of the plant during the day, and then move to the outside from dusk to dawn.
How can you control hornworms?
Handpick hornworms – the most effective control method in the home garden. Cut them in half, squish them, or drop them into soapy water and dispose.
Apply a natural insecticide BT (Bacillus thuringiensis, sold commercially as Dipel or Thuricide), especially when larvae are small. Thuricide is a natural formulation of a bacteria that is specific to leaf-eating insects. It's available as a concentrate in a couple of different sizes (Bonide Bt Thuricide 8 Oz. and Bonide Bt Pint). Many gardeners spray it as a precaution, even before hornworms appear.
Encourage natural enemies (rather than treat them). Braconid wasps (a parasitic wasp) sometimes lay white eggs on the hornworm and feed on it when they emerge. Leave them to help destroy tomato hornworms and other garden pests
Chemical insecticides that have been proven effective on the hornworm include carbaryl, permethrin, and spinosad.