Physical IPM Strategies for Remediating Kochia Patches for Canola, Wheat, and Pulse Production

Project Description

This project aims to evaluate physical control measures for kochia and to better understand the underlying abiotic and biotic ecology within kochia patches to accelerate remediation. Physical control measures for kochia are critically important due to the rapid development and spread of multiple herbicide resistance to Groups 2, 4, and 9 within kochia in Western Canada.

The main goal of the project is to understand the topography, biotic and abiotic soil conditions which favor kochia invasion and establishment, and to understand the longevity of kochia allelopathic presence within the soil and its impact on soil health to prevent reinvasion. This study will also explore the options for mulching techniques which may return infested areas to full yield potential. Understanding soil bacteria and fungi of these microhabitats will provide insights into microbial taxa that are associated with the decay of seeds, vegetation, and allelochemicals. Large patches of kochia will be identified and targeted for study on producer fields and experimental sites will be established within wheat, canola, and pulse crops.

The key objectives are 1) to assess effectiveness of physical control strategies in suppressing kochia emergence, 2) to characterize allelopathic chemicals and their subsequent persistence, 3) to characterize microbes which are associated with kochia infestations and populations which may enhance degradation of kochia seeds and organic matter, 4) to identify soil characteristics which either promote or alleviate kochia infestation persistence including salinity, and 5) to determine hydro-mulch longevity and ability to suppress weeds in the field.

The results of this project will provide an alternative control strategy which aims to control and remove kochia patches from agricultural production and thus increasing yield and decreasing production costs associated with managing kochia infestations.

Research Results

Kochia is an herbicide-resistant tumbleweed which infests Prairie field crops and disturbed areas in the environment. It is patch forming and typically found on field margins, low areas, sloughs, but can tumble in the wind across agricultural fields leaving seed in its wake. Kochia patch management is a targeted approach to manage this pest where it occurs in high density. This project evaluated physical control strategies for kochia patches on farmland. Kochia patches for study were identified by producers. Treatments included: black plastic mulch, coconut hydro-mulch, field chaff and straw, and mowing. Treatments were monitored for a three year period on their impacts on kochia. Kochia densities were monitored and soil samples taken in the fall to understand if kochia’s chemical defenses (allelochemicals) were persistent in the soils. Supplemental studies were conducted to further evaluate hydro-mulch stability in the field and effectiveness in the greenhouse. A small targeted survey of kochia patches was also conducted to confirm if kochia chemical defenses were persisting.
Uncontrolled patches had kochia densities reaching approximately 600 plants m-2 in 2021, 10,000 plants m-2 in 2022, and 1,200 plants m-2 in 2023. By the end of the 3-year study, mowing reduced kochia densities by 98% in the last measurement but required multiple applications per season. Field chaff and straw was very effective, it was applied to a depth of 63 mm in year one and reduced kochia densities by 86% in year one, 78% in year two, and 52% in year three. Plastic mulch was highly effective as kochia was unable to pierce the mulch but cropping will be challenging outside of plasticulture systems. The coconut hydro-mulch was applied to a 14 mm depth in year one and reduced kochia densities by 72% in year one but only 27% in year two and 39% in year three. Supplemental hydro-mulch evaluation indicates it may not be suitable for suppressing other weeds as no differences in generalized weed control were found. Greenhouse work indicates that hydro-mulch efficacy is likely linked to the availability of moisture and its ability to form a hard shell. No kochia chemical defenses were detected above the threshold for soils sampled in the fall, both for the field experiment and supplemental survey. This is promising to restoring the productivity of the soil once kochia is managed as no persisting effect was detected. Overall, the field chaff and straw treatment was the most promising as it used residual material from the harvested crop to smother kochia, prevent emergence, and remained effective for two to three years. While only the black plastic mulch was 100% effective, burying kochia patches in chaff will limit how many plants can grow and need to be treated with herbicide and may potentially develop resistance. The kochia densities observed in this study are very concerning as they are a hotbed for resistance risk, they contain a lot of plants to treat in a small area typically compared to the entire field.