Suitability of Wild Oat (Avena fatua), False Cleavers (Galium spurium), and Volunteer Canola (Brassica napus) for Harvest Weed Seed Control in Western Canada

Abstract

As chemical management options for weeds become increasingly limited due to selection for herbicide resistance, investigation of additional nonchemical tools becomes necessary. Harvest weed seed control (HWSC) is a methodology of weed management that targets and destroys weed seeds that are otherwise dispersed by harvesters following threshing. It is not known whether problem weeds in western Canada retain their seeds in sufficient quantities until harvest at a height suitable for collection. A study was conducted at three sites over 2 yr to determine whether retention and height criteria were met by wild oat, false cleavers, and volunteer canola. Wild oat consistently shed seeds early, but seed retention was variable, averaging 56% at the time of wheat swathing, with continued losses until direct harvest of wheat and fababean. The majority of retained seeds were >45 cm above ground level, suitable for collection. Cleavers seed retention was highly variable by site-year, but generally greater than wild oat. The majority of seed was retained >15 cm above ground level and would be considered collectable. Canola seed typically had >95% retention, with the majority of seed retained >15 cm above ground level. The suitability ranking of the species for management with HWSC was canola>cleavers>wild oat. Efficacy of HWSC systems in western Canada will depend on the target species and site- and year-specific environmental conditions.

Weed seed shatter in spring wheat in Alberta

“…In Saskatchewan, wild mustard seed retention at field pea and wheat direct-harvest stage was 90% or more (Burton et al 2016(Burton et al , 2017. Those studies noted similar results for cleavers, although Tidemann et al (2017) found only 62 and 50% retention in directharvested wheat and fababean, respectively. Kochia is often cut at the stem by crop harvesters before the seeds become mature (Mickelson et al 2004).…”

“…A recent study in central Saskatchewan found over 70% wild oat seed retention (i.e., up to 30% shattering) in spring wheat and field pea (Pisum sativum L.) at direct-harvest (direct-combining) stage (Burton et al 2016(Burton et al , 2017. In contrast, Tidemann et al (2017) found only about 30% retention in direct-harvested spring wheat and fababean (Vicia faba L.) in Alberta or Saskatchewan.…”

“…These practices can be one part of an integrated weed management system to reduce the seed bank, reduce reliance on herbicides, and thereby slow the selection of herbicide-resistant weeds. As quantified in studies in western Canada, weed seed retention to enable HWSC is favoured in early-maturing or competitive crops, and those that are swathed versus direct-harvested (Burton et al 2016(Burton et al , 2017Tidemann et al 2017). For example, seed shatter of wild oat in swathed canola (Brassica napus L.) (at 50% seed color change on the main stem) in Saskatchewan was less than 5% (Burton et al 2017).…”

“…Recent studies by Burton et al (2016Burton et al ( , 2017 and Tidemann et al (2017) have found significant differences and variation in seed shatter/retention both among and within weed species. Such variation may be associated with weed genotype or ecotype, crop or cultivar, agronomic practices, edaphic or environmental conditions, or their interactions.…”

“…The study was conducted in spring wheat. Experimental procedures followed that of Burton et al (2016) and Tidemann et al (2017). The experiment was arranged in a randomized complete …”