The Grim Reaper of Resistant Weeds

January 28, 2017 02:19 AM
 
The Grim Reaper of Resistant Weeds

The Australian-based Harrington Seed Destructor is a weed seed’s nightmare

The grim reaper of weed control is preparing to collect. The Harrington Seed Destructor (HSD) is a mechanical seed-destroying device with no peers. It chews through the tiniest seeds at harvest and spits out weed death. 

Initially designed as a combine pull-behind unit and expanded as a bolt-on, integrated version (iHSD), the seed pulverizing machine relies on the relative simplicity of cage mill technology. Two counter-rotating mills, which look like heavy-duty hamster wheels set in opposite motion, spin at more than 3,000 rpm and fracture passing weed seed as funneled chaff hits the crossbars at super-high speeds. No chopping or mashing required because the battering cycle is highly effective: steel on seed. The same technology used in the mining industry is unleashed on vegetation.

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At the forefront of HSD testing in the U.S., Jason Norsworthy, a weed scientist with the University of Arkansas, traveled to Australia in 2013 and met Ray Harrington, a farmer and inventor of the HSD. Norsworthy was stunned as he watched a pull-behind HSD in action and asked Harrington if the device was capable of destroying tiny Palmer amaranth seeds. 

“Ray asked me, ‘How does pigweed compare with rocks?’ Then he dumped in a 5-gal. bucket of gravel and out came powder,” Norsworthy says.

Every harvest, combines suck in weeds and spread billions of seeds per acre across farmland. It’s a devil’s bargain: Crops come in, but weed seed is scattered and the seed bank loads up for emergence the following spring. However, the escape of trillions of weed seeds into the soil after harvest is upturned by the HSD’s non-chemical technique and technology. Injured seeds with an open wound hit the dirt and get colonized by microbes within weeks. Death by nick or total mash-up is one and the same.

In the U.S., current HSD research is centered in Arkansas, Illinois and Maryland, with researchers testing different facets of HSD potential. In October 2016, Norsworthy trialed a borrowed stationary iHSD unit by funneling in chaff at a feed rate identical to a combine in operation. In a variety of tests, he laced rice, soybean and wheat chaff with seed from common weeds, including Palmer amaranth, morningglory, barnyardgrass and cockleburs. He is still collating data, but the results show extensive seed destruction: “Every Palmer seed I could identify was cracked, damaged or absolutely mangled. The HSD will help immensely in lowering seed numbers back into the field.”

Norsworthy has requested financial support from the Arkansas rice and soybean boards to purchase a mounted iHSD for field testing in 2017. Despite the promise of data and statistics, he wants real-time field testing at harvest to test canopy height differences and chaff moisture variations to present data to growers.

Adam Davis, a research ecologist with USDA-Agricultural Research Service (ARS) and weed scientist with the University of Illinois (UI), is conducting a five-year study to see how the HSD affects long-term weed resistance in field crops as part of an integrated weed management program. In 2015, he fed soybean chaff loaded with weed seeds (including waterhemp) through a stationary pull-behind HSD and recorded a minimum of 98% destruction for each species. 

Davis is testing the HSD on UI research acreage heavily infested with waterhemp. Roughly 20% of the trial field’s waterhemp is resistant to acetolactate synthase (ALS). Davis’ weed control study is combining HSD technology, tillage, cover crops and two herbicide programs. (One herbicide program intentionally increases ALS resistance and the other aims to kill the weed effectively.) Overall, he’s trying to achieve 85% to 90% weed kill through herbicides, and then stack the other tools, including HSD, on top to gain complete control. 

Built by de Bruin, an Australian manufacturing firm, the iHSD has no U.S. market entry date, but de Bruin officials say it could see limited release in 2019. Contingent on manufacturing location, shipping and distribution, de Bruin aims for a starting iHSD retail price below $100,000.

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The HSD’s pulverization factor lends itself to potential combine changes. In the fall of 2016, Davis harvested plots without the HSD pull-behind and collected weed seed in trays for examination. He found seed damage solely from the auger and combine fan, suggesting other equipment avenues to destroying seed. “What about a pounding system before it even reaches the HSD? One bit of damage and the seed is as good as dead in just a few weeks,” Davis says.

But reliance on HSD could open the door to select for weed genotypes that lose seeds early. “All management tools break through overuse. However, the HSD may bring tremendous help when used in complement with a weed management program,” he says.

In 2017, Davis will test the HSD in different cropping systems on larger acreages. As waterhemp issues consistently worsen in Illinois, he hopes for genuine success. On a farm just a few miles from his office, he’s battling a five-way resistant waterhemp population that’s one chemical away from becoming uncontrollable. 

“Resistant weed problems are changing quickly in Illinois,” he adds. “We better give our chemical controls some help from non-chemical tools.”

Steven Mirsky, a USDA-ARS research ecologist with the Sustainable Agricultural Systems Lab in Beltsville, Md., is testing the HSD on individual weed species to understand which ones are candidates for control. If a weed species drops seed prior to harvest, the HSD isn’t an option.

Mirsky is quantifying the seed patterns for a variety of species: How many seeds are produced; when do seeds drop; and how are they affected by the HSD’s cage mill technology. 

“We’re also examining how the HSD works as part of a multi-tactic weed management program,” he adds. “How does it work in the Mid-Atlantic region with herbicides, cover crops or other tools?”

Testing with a pull-behind, Mirsky has seen a high rate of seed destruction, particularly with Palmer. Long term, he believes the HSD is an ideal tool to stem weed resistance. “The HSD has to become part of standard weed control. It’s that impressive,” he says.

The HSD might not be the pale horse of weed seed death, but it might lead to genuine tactical change and become a benchmark weapon in the resistant weed wars. “Everyone in agriculture knows we’re running out of herbicides far faster than they’re coming to market,” Norsworthy adds. “An iHSD in the combine could be the future of destroying weed seed.” 

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