A new pathway for weed science at UC Davis
Better options for weed management in California vegetable crops.
For years California vegetable crops have been hand weeded to supplement the partial weed control provided by herbicides like DCPA, and pronamide. However, with a growing agricultural and industrial economy in Mexico, California is competing with Mexican farmers and factory owners for labor. The result is less labor available for California farms. However there is considerable interest in Europe for development of intra-row cultivators, as high labor costs and interest in physical weed control tools is much further along there than here. I am aware of three commercial intra-row cultivator models available: Ferrari from Italy, Stekettee IC-cultivator from the Netherlands, and Visionweeder from Denmark. These cultivators use machine vision to weed in the plant line by crop recognition based on pattern analysis, i.e., it sees the plant line. The cultivators remove weeds by pushing cultivator knives into the seedline to uproot weeds and withdrawing the knives to protect the saved crop plant. There also has been quite a bit of work in the area of robotic lettuce thinning, and since 2013 some commercial adoption has occurred in Arizona and California lettuce production districts. These devices spray an herbicide or fertilizer solution to reduce direct seeded lettuce stand from say 3 inches to 9 to 10 inch spacing. Standard practice for decades has been to use laborers with hoes to thin lettuce. Machine lettuce thinners have the potential to replace the hand thinning operation. Lettuce thinners also have the potential to remove intra-row weeds, but more research must be done in that area. Most of these robotic cultivators and lettuce thinners have been developed in the past several years, which is in stark contrast to the “old” herbicide situation. There are many new robotic options for weed management in vegetable crops, there are few or no new herbicides.
A future direction for UC Davis weed science.
Given the complexities of the California pesticide regulatory environment, a high urban population with strong anti-pesticide sentiments, the diverse set of crops in which to manage weeds, a shrinking pesticide industry, and a strong technology sector in Silicon Valley, it is very easy to make the argument that the future for robotic and physical weed control is bright in California and the future for herbicide development likely to remain stagnant. I would suggest that a weed science research focused on engineering of weed removal devices would be very productive here and would draw students from around the world. There is considerable need for better and faster crop and weed recognition systems, new devices for killing weed and weed seed banks with heat, sprays, steam or electrical impulses. In the past weed management has used a passive model delegating the creation of new weed removal tools, i.e., herbicides, to the agrochemical industry. When the agrochemical industry was active in the 1970's new weed control tools were created. When the flow of new herbicides diminished, little new development has occurred in the area of vegetable weed management. Meanwhile some useful products like diethatyl have been removed from the market, and for a time cycloate and DCPA were temporarily unavailable as there was no commercial supplier, and pronamide is now only registered on head lettuce not leaf lettuce. I argue for an active model in which robotic devices are created in collaboration with engineering partners, and made available commercially. The advantage to this approach is to develop weed control “devices” like intelligent cultivators, and avoid the regulatory quagmire in which pesticides operate.
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