Enhance understanding of cleavers populations in western Canada

Project Summary

Background

Cleavers is an increasingly problematic weed species in the Prairie provinces. It is a competitive weed that can also cause problems at harvest wrapping around equipment or introducing green, tough material into otherwise dry crops. Cleavers that tangle on equipment can easily be transferred between fields. This increases the risk of resistance by increasing genetic diversity in populations within a field as well as spreading resistant biotypes.

Preventing movement of weed seeds between fields is a best management practice (BMP) for reducing the risk of herbicide resistance (Norsworthy et al. 2012). Integrated weed management strategies are most effective when they are based on knowledge of the species biology. This is also a BMP for reducing the risk of herbicide resistance (Norsworthy et al. 2012). While biology of cleavers has been studied for many years (Malik and Vanden Born 1988), recent research by DeRoo (2016) suggested a shift in dominant species. This could change the efficacy of herbicide application strategies, shifts in emergence timing and may also suggest that other strategies could be more effective.

Purpose

This project aims to develop a better understanding of cleavers populations growing in western Canada and their variability which affects a producer’s ability to target this species. Cleavers is a common pest in western Canadian crops, and is increasing in abundance as well as in frequency of herbicide resistant biotypes. This research will characterize populations as well as biotypes in western Canada to determine emergence timing (particularly fall vs spring emergence), seed production and other biological characteristics. In addition the researchers aim to investigate which characteristics may be affected by maternal environment.

These two components combined will allow for the understanding of cleavers variability to be utilized by the researchers to develop and test integrated weed management studies for this species. Lastly, the project aim is to conduct a baseline screening on collected populations for quinclorac resistance. Quinclorac resistance has been previously identified in the province of Alberta and is believed to be at low levels within the cleavers population. This preliminary screening will allow the researchers to look for levels of resistance and may also provide resistant seed for future studies if found. Overall the goal is to increase understanding of cleavers biology and cleavers populations in western Canada and use this knowledge to better inform management strategies on a problematic and increasingly difficult to manage weed.

This study will result in an understanding of different cleavers biotypes that exist across the Prairies, their emergence phenology, and some of their biological characteristics, which will help in the development of integrated weed management strategies for managing a common pest in canola. Additionally, a baseline screening for quinclorac resistance will be conducted that can be used to do a very preliminary assessment of frequency of resistance and also potentially provide a source of seed for future studies. If quinclorac resistance is easily found in 30 randomly selected samples there would be an urgent need for further investigation into the frequency of this resistance biotype. The researchers may also be able to identify correlations between biotypes, plasticity, and developed resistance if any is found.

This project will also highlight biological characteristics such as length of emergence windows of cleavers – if it is a wide emergence window perhaps two in-crop applications of herbicide are necessary to really control the population, as an example. Understanding weed biology is the first BMP for reducing risk of herbicide resistance (Norsworthy et al. 2012). As a result, producers will be able to integrate biological information into their weed management strategies immediately in the field. The knowledge gained will also be used to help formulate and test a detailed western Canadian integrated weed management strategy for cleavers.

Objectives

The specific project objectives are to:

• Evaluate presence of cleavers biotypes on the Prairies based on emergence phenology, whorl/branch number close to maturity, seed production, and 1000 seed weight.
• Evaluate emergence timing of cleavers (assumed Galium spurium) populations on the Prairies.
• Determine if any of the above characteristics are affected by maternal environment.
• Screen collected populations for quinclorac resistance.

References

• DeRoo AC (2016) Determining the emergence timing, morphological characteristics, and species composition of Galium populations in western Canada. Thesis. University of Saskatchewan. 123 p.
• Malick N, Vanden Born WH (1988) The Biology of Canadian Weeds 86. Galium aparine L. and Galium spurium L. Can J Plant Sci 68:481-499.
• Norsworthy JK, Ward SM, Shaw DR, Llewellyn RS, Nichols RL, Webster TM, Bradley KW, Frisvold G, Powles SB, Burgos NR, Witt WW, Barrett M (2012) Reducing the risks of herbicide resistance: Best management practices and recommendations. Weed Sci Special Issue:31-62.