I simply don't understand
by Bob Hartzler
March 5, 2001 -  Anyone who reads farm magazines or listens to radio in farm country has learned not to expect all herbicide advertisements to make sense.  However, I believe a new 'ad' for mesotrione has reached new heights in the bewildering arena of herbicide marketing.  This new two-page 'ad' simply has a picture of a callistemon plant growing in the wild and points out that there are no broadleaf weeds anywhere near it.  On the second page are the words 'Mesotrione' and 'naturally' and a nice graphic representation of a plant seedhead.   No mention of who the manufacturer is or what product is being promoted is indicated anywhere in the ad.

Prior to seeing this piece I had never heard of callistemon.   My assumption was that this must be a plant that produces allelopathic chemicals.  A quick search of the internet determined that Callistemon is a genus of woody plants in the Myrtle family that is native to Australia.  This group of plants produces several secondary metabolites and essential oils.  Many allelopathic chemicals (plant compounds released into the soil that control or reduce the vigor of nearby plants) are related to these types of compounds.   Researchers from Zeneca Ag Products identified a compound from callistemon plants in the late 1960's that caused bleaching symptoms in plants.

You might ask why would anyone pay good money for a promotion such as this?  First some background.  Mesotrione is a new herbicide being developed by Syngenta for use in corn.  It represents a new class of chemistry, the triketones, and provides broadspectrum control of broadleaf weeds.   Mesotrione is related to the compounds first identified in callistemon plants back in the 1960's.   While mesotrione is not a 'natural' product, it is related to these compounds.   Thus the Callistemon bush and the 'Naturally' reference in this ad.  The product will be marketed as Callisto - and you wondered where they came up with that name.  The last I heard was that Syngenta is hoping for a label either in the second or third quarter of 2001.  I am assuming the rationale for this type of 'educational literature'  is that the EPA forbids promotion and marketing of products that have not yet received registration.  Thus, this marketing piece allows Syngenta to begin building product recognition for mesotrione before the product actually is registered.

An interesting fact I learned in my quest for knowledge is that callistemons have the common name of 'bottlebrushes'.  This name comes from the cylindrical, bottle-brush shape of the flower spike (the graphic in the 'ad').  Several species have been bred for use as ornamentals in landscapes.  The term 'bottle brush' also is commonly used to describe the symptoms appearing on corn roots following ALS-herbicide injury.  The triketones are pigment inhibitors (bleachers) and corn has shown an excellent level of tolerance to the product. Hopefully no one will try to link the two uses of the term 'bottlebrush' to imply this type of injury from mesotrione.

Thus, the purpose of this article is to answer questions of curious persons such as myself who have seen this piece of literature and wondered what in the world it meant (it also gave me a break from doing other, more productive stuff over lunch). 

Prepared by Bob Hartzler, extension weed management specialist, Department of Agronomy, Iowa State University