Weed Technology (2016) 30, 284-290

Lauren M. Schwartz, Jason K. Norsworthy, Bryan G. Young, Kevin W. Bradley, Greg R. Kruger, Vince M. Davis, Larry E. Steckel and Michael J. Walsh (2016)
Tall waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri) seed production and retention at soybean maturity
Weed Technology 30 (1), 284-290
Abstract: Two of the most problematic Amaranthus species in soybean production today are tall waterhemp and Palmer amaranth. This study determined the percentage of tall waterhemp and Palmer amaranth seed that was retained by the weed at soybean maturity to assess the likelihood of using at-harvest weed seed control tactics for soil seedbank management. Palmer amaranth plants were collected from fields in Arkansas, Tennessee, Illinois, Missouri, and Nebraska, and tall waterhemp plants were collected from fields in Nebraska, Missouri, Wisconsin, and Illinois. Collected plants were assessed for at-harvest weed seed retention in 2013 and 2014. Within 1 wk of soybean maturity, Amaranthus plants were harvested and the loose soil and debris beneath the plants were swept into a pan with a hand broom to collect any shattered seed. Percent seed retention ranged from 95 to 100% for all states both years, regardless of species. There was a strong correlation between weed biomass (g) and total seed production (no. plant^-1) in that the larger the plant, the more seeds it produced. However, there was no correlation between percent seed retention and weed biomass, which indicates that regardless of plant size and likely time of emergence, seed retention is high at the time of crop maturity. Overall, this study demonstrated that there is great opportunity for Palmer amaranth and tall waterhemp seed capture or destruction at soybean harvest. It is likely that nearly all of the seeds produced for both Amaranthus species passes through the combine during harvest to be returned to the soil seedbank. Thus, there is continued need for research focused on developing and testing harvest weed seed control tactics that aim at reducing the soil seedbank and lowering risks for evolution of herbicide resistance.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Kevin W. Bradley, Michael J. Walsh, Bryan G. Young

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution
control - general

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Amaranthus palmeri (weed)	Soybean (Glycine max)	U.S.A. (mid N)
	Amaranthus palmeri (weed)	Soybean (Glycine max)	U.S.A. (mid S)
	Amaranthus palmeri (weed)	Soybean (Glycine max)	U.S.A. (SE)
	Amaranthus tuberculatus (weed)	Soybean (Glycine max)	U.S.A. (mid N)