Good things come to those that wait. Well, when it came to getting a registration for prometryn for use on cilantro, wait we did. I recall doing the first trials on prometryn for use on cilantro in 1999. Since that time we worked closely with Becky Sisco at the Western Region of the IR4 Program to establish the tolerance for this material on cilantro. IR4 did their part and the packet was submitted to EPA. Given that cilantro is a very minor crop, the label was ultimately grouped with carrots, parsley and okra in order to attract more attention for the label request, and so that it would not get lost amongst the many other label requests that EPA deals with. The packet was ultimately processed and sent back to Syngenta, and in July, 2012 the label was issued for the use of prometryn on cilantro. That is the good news. It is interesting to note that during the extended amount of time that it took for the label to get issued, the production practices of cilantro changed. Cilantro used to be produced on 40-inch wide beds and was hand harvested and bunched. However, in the past 10 years the dominant production scheme changed to the use of high density 80-inch wide beds. Cilantro is still hand harvested to some degree in this new production scheme, but more commonly it is mechanically harvested which necessitates excellent weed control to provide a weed free product, and to keep hand weeding costs low enough to keep the crop profitable. Table 1 compares the relative weeding costs in the untreated control with excellent weed control provided by prometryn. The other preemergent herbicide registered for use on cilantro is bensulide. It provides useful weed control on sites with weeds such as purslane, pigweed and lambsquarter. However, it does not control nightshade and is therefore only partially reduces hand weeding costs at sites infested with this weed (see Table 1 and photos). This story illustrates the difficulties that growers face in profitably producing minor crops. The intensification of production practices further aggravates the critical need for effective weed control. Fortunately, the IR4 program is effective in establishing tolerances for a crop like cilantro, and eventually, the registrations do come through.
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