Plants that let caterpillars eat them and why that's a good thing

September 25, 2012

The way to (kill) a bug’s heart is through its stomach

Leave it to plants to show researchers how to fend off unwanted insects.  Two well known plant species are taking researchers to school on the best ways to eliminate pests, through their stomach.  Are their other cues we can take from plants?  The discussion topics can become quite intriguing.  

Review questions:

1.  What did the plants do to eliminate the insect larvae?

They produced an enzyme that reacted with the caterpillar's stomach contents to actively starve the caterpillar to death.

2.  What are the common names of the two plant species researchers studied in this article?

Tomato and potato

3. What chemical substance could the plants produce to ward off the insect larvae?

An enzyme called TD2 or threonine deaminase 2.

4.  Why is this newly discovered chemical important to crop management?

The enzyme could lead to new forms of pesticide.

5.  What is so different about this chemical defense developed by these plants compared to others?

This enzyme only works after the caterpillar has consumed it.  Once the enzyme reaches the stomach, then it activates to starve the caterpillar.

Extension question: (or if you really want to make your students think)

What are some common chemical or other defenses that plants use to fight off herbaceous, animal, and insect pests?

  • Pine trees exude sap to trap insects trying to bore into the cambium.
  • Oak trees use the tannins in their leaves as well as dense shade from their canopy to inhibit growth of other plants.
  • Many species of plants have thorns that prevent animals from browsing on them.
  • Lantana and a few other landscape plants have a bitter taste that white-tailed deer do not like.