WMDs In My Garden.

17 July 2007


No, they aren’t the components for a uranium centrifuge. But rather, myriad mustard oil bombs, set to detonate. A new paper from Imperial College outlines how cabbage aphids (Brevicoryne brassicae) mimic the chemical defenses of their plant hosts.

The characteristic spicy tang of mustard family plants (broccoli, cabbage etc.) is, as with many of the flavorful plant compounds we humans seem to enjoy, a toxic chemical weapon. In the case of mustard oil, the toxin is actually created when several precursor chemicals are released as the cells of the plant are being destroyed by the would-be mustard eaters.

Cabbage aphids feeding on brassicas ingest plant compounds and metabolism them into the same precursor chemicals that the plants use to ward off herbivores.  And who are the aphids warding off? Why, our old friends, the ladybirds (among others)…


but, shown here actually eating a black bean aphid (Aphis fabae) less noxious fare perhaps ?

The researchers found that ladybird larva did not survive to adulthood when fed on a diet of wingless cabbage aphids who carried a high volume of sinigrin, one of the chemical precursors to mustard oil. The winged form of the aphids was apparently less toxic, perhaps suggesting a shift in defense strategy from chemical defense to flying escape.

Here’s the abstract. And here’s the Science Daily take. And here’s a nice diagram of the cabbage/turnip aphid forms.

Peace!  oh yeah, and death to aphids!

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