Enhanced understanding of cleavers populations in Western Canada

Term: 4 years, ending April 2025
Status: Completed
Researcher(s): Breanne Tidemann, Charles Geddes, Shaun Sharpe, Hiroshi Kubota, AAFC; Christian Willenborg, USask
SaskCanola Investment: $51,800
Total Project Cost: $103,600
Funding Partners: Alberta Canola Producers Commission

Project Description

If nothing else, cleavers serve as an indicator that rain has been received at some point in the growing season. Moisture is an absolute driver of cleavers emergence, both in the fall and in the spring. Environment then plays a role in cleavers survival and productivity, and environment at seed production also plays a role in how many of those seeds germinate the following year. While the growth of cleavers in fall versus spring may seem random, there are some clear driving factors behind it. Additionally, it’s more important than ever to monitor results of herbicide applications on cleavers as there is evidence of reduced control in some populations.

Twenty-five cleavers populations were collected from across the Prairie provinces. Those populations were then seeded together in both the fall and the spring in three environments: Lacombe and Lethbridge, AB, and Scott, SK. This allowed researchers to look at how populations reacted under different environments and to select 10 populations with diverse characteristics to move forward to the next year. The following year spring and fall trials were again set up with the 10 selected populations but with seed from each of the three locations from the previous year. For example, the population SK01 was selected for the study and emergence levels of SK01 seed grown in three different maternal environments (Lacombe, Lethbridge, and Saskatoon) were compared to determine if effects on emergence were purely genetic or also influenced by maternal environment during seed development. . Finally, they used the 25 original populations and screened them unreplicated in Saskatoon and Lacombe with a field rate of quinclorac (Facet L, plus Merge as per label). The following year we conducted a replicated study in Lacombe and a dose response study with select populations in the greenhouse in Saskatoon.

Researchers confirmed with the populations used in this study that false cleavers (Galium spurium) is the more common of the Galium species in the Prairies. Emergence of false cleavers (hereafter cleavers) is driven by moisture, although there is a range of timing linked to different populations. Fall emergence provides opportunity for cleavers to be at an advanced stage at the spring-burn-off timing which means significant late-season precipitation events should lead to increased scouting for cleavers emergence and possibly fall herbicide applications for management. Winter survival is high in areas that are commonly afflicted with cleavers (black soil zone areas). Maternal environment and dry conditions at seed set seem to lead to increased emergence ability of cleavers (increased emergence) or decreased dormancy compared to environments with more moisture at maturity. A number of populations showed limited control with quinclorac in the field. Dose response studies show no real difference in biomass production, however these populations are showing increased survival with increasing rates of quinclorac. This may be related to drought conditions during the period of the study resulting in increased cuticle production or it could be some form of low-level resistance beginning to occur. It’s not the same as what was observed in the 1990s. Further investigation is needed into this area. A side observation resulted in the findings that cleavers can be infected with aster yellows. More investigation is needed to understand the impact of the disease on reproduction and seed viability.

Grower Benefits

Cleavers emergence, both fall and spring is driven by moisture. Fall seasons with a number of precipitation events should see increased scouting for cleavers emergence. Cleavers can and will flush, so precipitation events should trigger scouting prior to in-crop herbicide applications for their presence. Dry conditions at seed set timing may lead to increased emergence the following year. Applications of quinclorac may not result in plant death and injured plants that survive can produce a large quantity of seed that goes into the seedbank. Post-application scouting is critical to managing any survivors of these herbicide applications.

Objectives

1. Evaluate presence of cleavers biotypes on the Prairies based on emergence phenology, whorl/branch number close to maturity, seed production, and 1,000 seed weight.

2. Evaluate emergence timing of cleavers (assumed Galium spurium) populations on the Prairies.

3. Determine if any of the above characteristics are affected by maternal environment.

4. Screen collected populations for quinclorac resistance.