Prefar (bensulide) is an organophosphate herbicide that has been used for more than 50 years in Arizona for lettuce production. In fact, it is one of the standard herbicides used for this purpose.

The University of Arizona Vegetable IPM Team conducted a Yuma County and Imperial Valley Survey evaluating a portion of the acres checked by Pest Control Advisors. The 2017 data indicated that in 58% of the lettuce acreage reported was treated with Prefar. Similarly, in the 2018 survey 52% received a Prefar application.

This product performs well when incorporated with sprinkler irrigation at stand establishment. It also works best in course textured soil’s such as the ones found in Coachella Valley, California. One of the weeds controlled by Prefar is pigweed (Amaranthus palmeri), which was found to be resistant to glyphosate herbicide in Arizona by Dr. William B. McCloskey in 2012. Other weeds are purslane (Portulaca oleracea), goosefoot (Chenopodium murale), Lambquarter (Chenopodium album), and some species of grasses.

The list of crops in which bensulide is used demonstrates the importance of this weed control tool for the agricultural industry.
According to the 1080 Pesticide Use Reporting Database provided by the Arizona Pest Management Center the list of crops includes: Arugula, Bok choy, Broccoli, Brussel Sprouts, Cabbage, Cantaloupe, Cauliflower, Celery, Cilantro, Corn, Cress, Endive, Fennel, Mustard, Kale, Lettuce, Onion, Parsley, Squash, Swiss chard, and others.

Please read the following contribution from Dr. Al Fournier on the EPA Notice- Petition to Revoke Organophosphate Tolerances: (including Bensulide).
 

Petition to Revoke Tolerances and Cancel Certain OP Uses: Comment Deadline Extended 

Al Fournier, IPM Program Manager, Arizona Pest Management Center

 10 August 2022

The EPA has extended its deadline for public comment on a Petition to Revoke Tolerances and Cancel Registrations for Certain Organophosphate Uses until September 25, 2022.
 
The petitioners, including United Farm Workers, Earthjustice, and several other groups, request that the Agency revoke all tolerances and cancel all associated registrations for food uses of 15 listed OPs, and further requests that the Agency complete its registration review process for these chemicals no later than October 1, 2022. The pesticides are currently at various stages of review, and the proposed deadline does not align with EPA’s published schedule to complete scientific reviews.
 
Among 15 Organophosphates named in the petition are 10 with reported uses in Arizona (bolded below). Those with known uses in lettuce and other produce include Bensulide (Prefar) and Acephate (Orthene).
 
Acephate, Bensulide, Chlorethoxyfos, Chlorpyrifos-methyl, Diazinon, Dichlorvos, Dicrotophos, Dimethoate, Ethoprop, Malathion, Naled, Phorate, Phosmet, Terbufos, Tribufos
 
Read the full EPA Notice here: https://www.regulations.gov/document/EPA-HQ-OPP-2022-0490-0001
 
To submit comments to the docket, use the following link: https://www.regulations.gov/commenton/EPA-HQ-OPP-2022-0490-0001
 
To contribute to Arizona Pest Management Center comments, contact Al Fournier