There are more than 50 broadleaf and grass weeds in this area that are common and have been here for a long time.  It would be great to have an herbicide that will control all of them, be safe to the crop and be gone the next day after harvest.

Obviously, we are a long way from achieving this. What we have done instead is select for the weeds that escape our weed control practices. Anything that shifts the advantage to the crop instead of the weeds will help. Our practices include the use of herbicides, mechanical techniques and hand hoeing. Good weed control can be achieved using all three but may not be economical.

Weed selection due to herbicide availability was evident a few years ago when leaf lettuce was removed from the Kerb label in 2009. It is well known that Kerb, Prefar and Balan were the standard herbicides used in lettuce for the last 60years. Kerb will control the grasses and most of the broadleaves consistently including many that are not controlled by the other two products such as shepherds purse, london rocket and wild mustard. The longer that Kerb was unavailable the more prevalent some weeds would become. On January 12, 2016, the EPA label for Kerb was reinstated for leaf lettuce bringing back the tool to the industry1.

Prefar will control grass consistently, purslane and pigweed most of the time, lambs quarters and goosefoot some of the time. Balan will control grass consistently and many of the small-seeded broadleaves some of the time.

The postemergence grass herbicides were registered about 30 years ago but for broadleaf weeds there has not been a new registration in half a century.

Reference:
1.    Retrieved from the www on Oct 14, 2024 https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=21270#:~:text=On%20January%2012%2C%202016%20the%20Federal%20EPA,55%20day%20prior%20to%20harvest%20(Table%201).

2.    https://cales.arizona.edu/crop/vegetables/advisories/more/weed122.html