The Tobacco Hornworm: Expert Communicators

When I was a child, summer meant one thing to me.  Camp.  Every year I would go off to a camp in Wisconsin for a week or two, and I loved it.  One of the sure signs of summer was the moths.  You never really saw them during the day, but at night they would appear out of nowhere and flock towards the few lights we had.

They were on everything: screens, tents, buildings; nothing was immune to the moths.  Although never my favorite bug (if I were to have one!), they have honestly always fascinated me.  Recently, I came across an article that talked about one of the amazing abilities moths have.

The Manduca Sexta or Tobacco Hornworm is an amazing moth.  Common in southern states, this moth tends to have two generations per year.  While the moth may look pretty, its caterpillars can be disastrous for gardeners.  Most of the time, this moth lays its eggs on tobacco and tomato plants, however, they sometimes do so on peppers and eggplants.

When the adult moth lays its eggs, it generally puts them on the bottom side of the leaves.  Once the eggs hatch, the caterpillars slowly begin to feed on the plant.  They are almost invisible because of their color and can easily go undetected.  They can even stay inside the plant during the day to avoid predators.

While they starts out slow, during their last week of growth, the caterpillars consume everything!  They quickly expand in size and can completely defoliate the plants in just a couple of days.  Either after the plant is consumed or the caterpillar grows too heavy, it falls to the ground and buries itself to make its cocoon, leaving the plant destroyed.

In order to protect themselves both the plants and the moths have developed different skills.  When the plant is injured, it releases green leaf volatiles (think of the smell of freshly cut grass).  This odor can act as a repellent, but it also can attract predators of the caterpillars to the plant.

Although this method is used to protect the plant, the Tobacco Hornworm moth has developed the ability to detect these signals.  When the moth senses the green leaf volatiles, its brain sends out an indication that the plant isn’t safe.  It connotes that either there are already other caterpillars there, which would mean competition for resources, or that the plant is susceptible to predators.  Because of this, the moths are able to find plants that aren’t releasing the green-leaf volatiles and safely lay their eggs.

Since the moths have this ability, it can be hard to stop them before they consume the entire plant.  One way that has shown promise is applying artificial odors around the plants that mimic the green leaf volatiles.  Another way is just picking them off.  Often the caterpillars start their meal at the top, and if people are aware, they can stop them before they get any further.  Lastly, if a person is too late to save their current plant, they might be able to prevent it from happening again by tilling up the soil surrounding the damaged plant.

If you have a moth problem or are in need of pest control services, be sure to contact Ehrlich with any questions.

How do you feel about the Tobacco Hornworm’s amazing ability? Share below in the comments!