Schneier on Security
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November 29, 2011
Security Systems as a Marker for High-Value Targets
If something is protected by heavy security, it's obviously worth stealing. Here's an example from the insect world:
Maize plants, like many others, protect themselves with poisons. They pump their roots with highly toxic insecticides called BXDs, which deters hungry mandibles. But these toxins don’t come free. The plant needs energy to act as its own pharmacist, so it distributes the poison to the areas that deserve the greatest fortification -- its crown roots.
Maize seedlings grow roots either from the embryo itself (embryonic roots), or from the growing stem (crown roots). Christelle Robert found that the crown roots are especially important. They contain the most nutrients, and their loss matters more to the seedlings. As such, they receive the greatest investment of BXDs; they contain five times more of one particularly toxic compound called DIMBOA.
So, if plant-eating insects want to nibble on the most nutritious roots, they also swallow the highest amount of poison. Instead, they target the more lightly defended embryonic roots, which are less valuable to the plant. But the Western corn rootworm ignores these rules of engagement.
The larva of this beetle eats the roots of maize, corn and other cereals and it’s a significant pest that can ravage entire crops. Its success stems from its ability to turn maize’s defence against it. Robert found that the rootworm, unlike other insects, ignore the embryonic roots and head straight for the crown ones.
When Robert gave rootworms a mutant plant that couldn’t produce BXDs, it lost its interest in the crown roots. Rather than being deterred by the plant’s poisons, the rootworm actually uses them to track down the most nutritious meals.
The rootworms are immune to the poison, of course. Otherwise the trick wouldn't work.
Paper, behind a paywall.
Posted on November 29, 2011 at 2:13 PM
• 16 Comments
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A similar finding - using the toxin to find a plant host in addition to nutrition:
Journal of Chemical Ecology, Vol. 18, No. 7, 1992
6-METHOXY-2-BENZOXAZOLINONE: A SEMIOCHEMICAL FOR HOST LOCATION BY WESTERN CORN ROOTWORM LARVAE
"Many plant species contain specific allelochemicals that provide an effective toxic defense against herbivorous insects (Waller, 1987). Despite this, even a plant species that is chemically well defended may be attacked successfully by a few specialist insect species that not only withstand a particular plant toxin, but use it as a semiochemical to locate and recognize their plant host (Waller, 1987; Harborne, 1988; Rosenthal and Janzen, 1982). No examples of this have been reported for insect herbivores of maize, one of the principal agricultural plant species worldwide. We now report that an important toxin produced by maize and other grasses, 6-methoxy-2-benzoxazotinone (MBOA), is used as a semiochemical for host location by western corn rootworm larvae."
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