Alicia Merriam

Miss Alicia Merriam

Higher Degree by Research Candidate

School of Agriculture, Food and Wine

Faculty of Sciences, Engineering and Technology

I am a PhD candidate in the Weed Science research group at the University of Adelaide's Waite Campus. My project aims to understand the extent, distribution and management of herbicide resistant common sowthistle and prickly lettuce, particularly in lentil crops.

Prior to joining the Weed Science Research Group I lived in Canada and obtained a Bachelor of Science in Agriculture from the University of Saskatchewan. During my degree I worked as a research assistant for the Canadian federal department of agriculture, where I participated in weed surveys and developed a love of field work.

In my spare time I enjoy socializing, spending time outside, and stopping to smell the wildflowers.

Herbicide-resistant common sowthistle and prickly lettuce: 
Dispersal, seed biology and management considerations in lentils.

Supervisors: A/Prof Christopher Preston, A/Prof Gurjeet Gill and Dr Jenna Malone

Prickly lettuce (Lactuca serriola L. or wild lettuce) and common sowthistle (Sonchus oleraceus L. or milkthistle) are two common weeds in the southern cropping region of Australia, and both are problematic particularly in weakly competitive crops such as lentils. They compete for space, water and nutrients both within and outside of the growing season as well as causing problems at harvest. Both species have evolved resistance to herbicides from Groups B, I and M. Due to the wind-borne nature of their seeds, these species can move across the landscape and this is a commonly cited example of why they can be difficult to control. As a result, management tends to be reactive rather than a more proactive Integrated Weed Management (IWM) approach. However, the extent to which seeds move and the role this movement plays in the spread of herbicide resistance is not known. This project will aim to understand gene flow in these species and its implications for management, as well as examine how they might be evolving in response to intensive lentil production.

The main objectives of this project are to:

  • Determine the extent of herbicide resistance in common sowthistle and prickly lettuce in the southern cropping region, particularly in lentil production areas.
  • Determine how much seed moves and how far it travels from parental plants.
  • Establish how effective management during the cereal phase is in controlling weed numbers in the following lentil crop.
  • Determine if and how seedbank biology of these species has evolved in response to intensive lentil production. Are weed seedlings emerging later in the year to escape knockdown and pre-emergent herbicides, and how much of the seedbank is carrying over to subsequent years?

This project will increase knowledge about the extent and evolution of herbicide resistance, field ecology and seedbank biology, of common sowthistle and prickly lettuce. These insights will improve management strategies for these problematic broadleaf weeds, which will help lentils remain a profitable crop by maintaining sustainability of production.

For more information see the Weeds Research Group Website

Common sowthistle flowers in a lentil crop

  • Journals

    Year Citation
    2021 Merriam, A. B., Malone, J., Gill, G., & Preston, C. (2021). Can rotations improve management of herbicide-resistant annual sowthistle (Sonchus oleraceus) and prickly lettuce (Lactuca serriola) in lentil production systems of southern Australia?. Weed Technology, 35(4), 532-538.
    DOI Scopus2 WoS3
  • Conference Papers

    Year Citation
    2018 Merriam, A., Boutsalis, P., Malone, J., Gill, G., & Preston, C. (2018). Extent of herbicide resistant common sowthistle (Sonchus oleraceus) in southern Australia. In Proceedings of the 21st Australasian Weeds Conference (pp. 16-19). online: AWC.
  • Conference Items

    Year Citation
    2018 Krishnan, M., Petrovic, T., Valappan, G., Merriam, A., & Preston, C. (2018). Understanding the mechanism of 2,4-D resistance in Sonchus oleraceus (Common sowthistle). Poster session presented at the meeting of Weed Biosecurity - Protecting Our Future. Sydney.

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