University of California

Posts Tagged: Weeds

Taking the drudgery out of weed control

For automated, mechanical weed control to work, scientists must teach machines how to distinguish between unwanted vegetation and the crop being cultivated. A new, high-tech system using x-rays to detect tomato stems is under development by UC Davis Cooperative Extension agricultural engineer David Slaughter and USDA Agricultural Research Service researcher Ron Haff. The output from the x-ray detector is input to a microcontroller that controls a pair of pneumatically powered mechanical weed knife blades.

Slaughter and Haff's work was explained this week in an online newsletter produced by Vision Systems Design, an organization that provides automation solutions for engineers and integrators worldwide.

The mechanical weeding machine includes an x-ray mounted to the side of a shielded tunnel that is pulled behind a tractor over the row of tomato plants. As the x-rays radiate across the tunnel, they are detected by an array of 32 photodiodes whose output is tied to a single point at the input of a summing amplifier, the story says.

The system was used in field trials on a 15-meter row containing 39 standing tomato seedlings. At a speed of about 1 mile per hour, the detection system identified all 39 stems of standing plants with no false positives.

Tomato field infested with field bindweed.
Tomato field infested with field bindweed.

Posted on Thursday, December 17, 2009 at 10:07 AM
Tags: David Slaughter (2), mechanical (1), tomato (3), tomatoes (12), weed control (2), weeds (7)

California Agriculture journal reports on resistant weeds

The July-September 2008 issue of California Agriculture journal includes a science brief and a research article documenting increasing resistance to the common weed killer glyphosate in California weeds. The most common brand name for the herbicide is RoundUp.

In 2005, UC weed researchers Anil Shrestha and Kurt Hembree notified the media that they had confirmed glyphosate resistance in horseweed. In 2007, a news release by Stephanie Klunk of the UC Integrated Pest Management program reported on glyphosate resistance in hairy fleabane.

The California Agriculture science brief says at least 14 glyphosate-resistant weed species have been reported, threatening the loss of the herbicide.

"Because of its (glyphosate's) ease of use, environmental safety and effective control of weeds, it is important to maintain the viability of glyphosate in California," Shrestha is quoted in the brief. It says experts suggest using a variety of weed control tactics, not glyphosate alone, to reduce resistant weeds.

The research article details research by Shrestha, Hembree and USDA research agronomist Bradley Hanson that confirmed the hairy fleabane resistance.

Hairy fleabane that survived glyphosate applications.
Hairy fleabane that survived glyphosate applications.

Posted on Tuesday, July 8, 2008 at 10:24 AM
Tags: weeds (7)

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