Fate of weed seeds after HSD processing in Midwestern and Mid-Atlantic United States

Authors: SHERGILL, LOVREET - University Of Delaware; BEJLERI, KRESHNIK - University Of Maryland; Davis, Adam; Mirsky, Steven

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2019
Publication Date: 12/5/2019
Citation: Shergill, L., Bejleri, K., Davis, A.S., Mirsky, S.B. 2019. Fate of weed seeds after HSD processing in Midwestern and Mid-Atlantic United States. Weed Science. 68:92–97.

Interpretive Summary: Widespread dependence on too few herbicides has promoted the development of herbicide-resistant weeds (i.e., weeds no longer controlled by one or more herbicides). Herbicide resistant weeds pose a significant threat to cash crop yield and must be controlled to protect the economic viability of farms. Farmers and researchers are investigating non-herbicide methods of weed control such as harvest weed seed control (HWSC). Australians have developed a trailer mounted machine that is towed behind a combine, called a Harrington Seed Destructor (HSD), that destroys weed seeds in chaff at harvest. However, the HSD has never been tested on weeds common to soybean production systems in the Midwest and Mid-Atlantic US. We tested the HSD under laboratory conditions to determine its efficacy in destroying the seeds of seven common Midwestern and five common Mid-Atlantic weed species. On an average, the HSD completely destroyed 97% of weed seeds in the first run and 96% of weed seeds in the second run of the experiment. We buried the remaining large seed fragments to determine whether they were still viable. We observed that the damage inflicted by the HSD promoted seed mortality over winter. These results clearly demonstrate that the HSD is highly effective in promoting seed mortality and could potentially be used as a HWSC tactic for weed management in the Midwest and Mid-Atlantic US. The results of this work will serve as the basis for future development of HSD applications and inform equipment manufacturers on the potential of the HSD in impacting herbicide-resistance management in US food systems.

Technical Abstract: The Harrington Seed Destructor (HSD), a harvest weed seed control (HWSC) technology that destroys weed seeds in seed-bearing chaff material during grain crop harvest, has been highly effective in Australian cropping systems. However, the HSD has never been tested in soybeans and weeds common to soybean production systems in the Midwest and Mid-Atlantic US. We conducted stationary HSD testing and winter burial studies during 2015-2016 and 2017-2018 to determine (i) the efficacy of the HSD to target weed seeds of seven common weeds in Midwestern and five in Mid-Atlantic US, and (ii) the fate of HSD-processed weed seeds after winter burial. The HSD destroyed 93.5-99.8% of weed seeds in 2015 and 85.6-100% of weed seeds in 2017. The percent seed destruction by HSD showed a very weak negative correlation with 100-seed weight in 2015, but a weak positive correlation was observed in 2017. The weak relationships (positive or negative) between seed size and seed destruction by HSD, and high percentage of weed seed destruction by HSD across all seed sizes indicate that the biological or practical effect of seed size is limited. The HSD-processed weed seeds that retained at least 50% of their original size, labeled as potentially viable seed (PVS), were buried for 90 d over winter to determine the fate of weed seeds after winter burial. At 90 d after burial (DAB), the HSD-processed PVS were significantly less viable than unprocessed control seeds, indicating that HSD processing physically damaged the PVS and promoted seed mortality over winter. A very small fraction (< 0.4%) seed of the total weed seed processed by HSD remained viable after winter burial. The results presented here demonstrate that the HSD is highly effective in increasing seed mortality and could potentially be used as a HWSC tactic for weed management in this region.