The cost of the kill-step ingredient sprayed on unwanted plants is perhaps the largest challenge in automated thinning. The best product to kill unwanted plants may not be economically feasible for growers.

Vegetable grower Davie Brooks has grown vegetables for 37 years for Pasquinelli Produce. The company farms 9,000 acres of winter vegetables in the Yuma area.

Brooks says the worsening farm worker shortage opened the door to the development of automated thinners. He started work on an automated lettuce thinner a decade ago in the farm shop. He later handed the torch to others.

Current automated thinners on the market do not perform as well as hand thinning, says Brooks. Machine accuracy still has a way to go.

“When they perfect a machine I will probably buy one,” Brooks said. “I am not going to buy a thinner that can’t at least do as good of a job as a hand crew.”

Brooks is confident the machines will get better.

He reflected, “If they can send a man to the moon I’m sure they can figure out how to thin lettuce with a machine.”

Brooks is concerned about the cost of the material to kill unwanted plants. Acid-based fertilizer is cost prohibitive, he says. Plus, the material must be labeled for thinning use.

“For some reason, people don’t want to use lower cost sulfuric acid mixed with water,” the grower said. “They think it’s too dangerous to use.”

“That’s malarkey,” Brooks said. “Just figure out how no one can get hurt. Sulfuric acid is the cheapest product and kills unwanted plants fast.”

Richard Smith has spent the last five years evaluating the entire automated thinning process, including spray materials.

“The (overall thinning) machine works well but the grower needs the right material to spray to take out unwanted plants,” Smith said.

Over the years, a wide variety of kill methods have been tested including mechanical blades, flames, steam, electricity, and others.

Among the products which shows good promise, Smith says, is the herbicide product Shark.

What is the next step in automated lettuce thinners? One idea is to add a boom to the thinner machine to spray a needed nutrient, insecticide, or fungicide on plants kept in the bed. This could reduce production costs, including one less trip down across the field.

Smith is excited about the future of automated thinners.

“It’s just getting started.”

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