New herbicide for T&V crops...

... well, a new name and new uses for a familiar product anyway. 

I received a notification today that Dow AgroSciences received California registration for Trellis^TM herbicide for use in grapes and tree nuts. 

The active ingredient in Trellis, isoxaben, may be familiar to folks who have used Gallery T&V herbicide which was registered in 1998.  This is a residual herbicide that will provide several months of control for a fairly broad range of broadleaf weeds (minor activity on some grasses).  For more info, go to the UC Weed RIC "herbicide susceptibility chart" and scroll down to isoxaben (Gallery) in the herbicide window or read the Trellis label attached to the bottom of this post.

Trellis will be replacing Gallery T&V for tree and vine crops.  The biggest difference between the products (besides a new name and marketing campaign) is that Trellis will be labeled in bearing and non-bearing tree nuts and grapes.  However, like Gallery, Trellis will continue to be labeled for non-bearing stone and pome fruit crops.  For more information on tree and vine registrations, you can see the annually-updated herbicide registration chart at this link. 

For those that keep track of these sorts of things (that's all of you, right?), isoxaben is a cellulose biosynthesis inhibitor (CBI) in the benzamide herbide family (WSSA Group 21).  This means that the mode of action of this herbicide is to disrupt the formation (biosynthesis) of new cellulose.  Cellulose is a very important component of cell walls - plants that cannot form new cell walls (for new cells or to replace worn out components) are not able to grow or survive.

Being a Group 21 herbicide, isoxaben offers a different mode of action than other common herbicides used in tree and vine crops - using different modes of action can reduce the selection pressure for herbicide resistant weeds.  Many of our common tree and vine herbicides affect other biosynthetic pathways like aminoacid synthesis (glyphosate and rimsulfuron affect two different amino acid synthesis pathways) or PROTOX (long, hard-to-pronouce enzyme) inhibitors like oxyflourfen, saflufenacil, and carfentrazone as well as several other modes of action.  Read more of an intro to herbicide mode of action here.

Isoxaben is a preemergence herbicide that affects germinating seeds and very small seedlings as they first sprout.  Affected plants usually do not emerge from the soil at all.  This herbicide does not have any postemergence activity and will not control existing plants but can be tank mixed with other herbicides to control existing vegetation.