Kochia, Bassia scoparia L.
This content is an excerpt from the Getting Rid of Weeds Through Integrated Pest Management website. For the complete report on Kochia please visit the growiwm.org website.
Kochia (formerly Kochia scoparia) is a summer annual broadleaf weed species native to Eurasia and was introduced to the Americas as an ornamental in the mid to late 1800s by European immigrants. It is also known as burning bush, mock-cypress, Mexican firebush, and Mexican fireweed. Ornamental kochia escaped cultivation and formed naturalized populations that now occur throughout most of the continent, especially in arid and semiarid environments. The ability to grow in dry, saline soils has led to adaptation and widespread distribution of kochia in the arid west and semi-arid Great Plains.
- Kochia is common in rangeland, pastures, and crop production systems where it has adapted and thrives in semiarid to arid regions of North America.
- It is also commonly found along roadsides, ditch banks, railroad tracks, and in other disturbed sites as a ruderal species.
- Kochia has a wide window of emergence due to the unique ability to germinate at low temperatures as early as January and continue to emerge throughout the summer into July.
- Kochia will grow vegetative throughout the spring and summer before flowering; it can produce copious amounts of pollen.
- In the fall, fully senesced mature kochia plants will detach at the soil surface and tumble across the landscape, dropping seeds with each impact, in a wind-driven process that spreads seeds long distances.
Herbicide resistant kochia trail created by a resistant mother plant being blown across the field the previous fall, dispersing its progeny as it tumbled. The chem-fallow field was then bulk sprayed with RoundUp to remove the susceptible kochia, leaving this pattern of resistant individuals. Image credit: Phil Westra, Colorado State University.
Mature kochia plant growth above the wheat canopy near time of harvest in Colorado. Image credit: Eric Westra, Colorado State University.
Kochia growth in corn showing relative competitive ability. Image credit: Eric Westra, Colorado State University.
Kochia seedling growing through no-till residue. Image credit: Eric Westra, Colorado State University.
Button stage of Kochia with dense fine leaf hairs covering the top side of leaves. Fine hairs can suspend herbicide above cuticle significantly reducing foliar absorption. Image credit: Eric Westra, Colorado State University.
Kochia leaves are alternate with simple blades that are highly pubescent and arise on erect, highly branched stems. Kochia flowers are inconspicuous without petals, and on a given flower the stigmas emerge prior to anther development which facilitates cross pollination between plants. Flowers develop in clusters in the axils of upper leaves and in terminal spikes. Seeds are around 1.5 mm long and develop in star shaped fruit that are brown and flattened. Kochia has a shallow taproot which can be easily pulled or hoed out at early growth stages. Once fully matured, an abscission layer near the soil surface allows for whole plants to detach and bounce across the landscape dropping seed in a wind-driven process known as ‘Tumble mechanism’.
Kochia growth and architecture is highly influenced by inter and intraspecific competition. When growing with competing vegetation, growth is more erect, single stemmed and taller; when growing in the absence of competing vegetation, it is more bushy and multi-branched with a larger plant diameter. In moderately dense kochia stands that promote erect, taller primary axis growth, plants can get over six feet tall. While in low competition environments high light intensity suppresses apical dominance and lateral growth resulting in plants typically around three feet tall with oval growth forms and a diameter similar to its height.
Small emerging kochia seedlings have leaves that are densely covered in small, fine, white hairs in what is commonly referred to as the button stage. Herbicide applications during button stage are discouraged (as often stated on herbicide label) as leaf hairs can reduce foliar absorption of herbicides by suspending droplets above the leaf cuticle on the leaf hairs.
Around two weeks after seedling emergence, leaf hair density decreases as leaves grow. After the button stage, kochia leaves maintain fine leaf hairs on the bottom of the leaf, while leaf tops are smooth. It is common to see high seedling densities, especially around the location where the parent plant was growing before detaching from the soil when mature. This is often referred to as a “kochia mat.”
Kochia seedling growing through no-till residue. Image credit: Eric Westra, Colorado State University.
Kochia plant with wide leaves (~0.5 inches). Image credit: Eric Westra, Colorado State University.
Herbicide resistant kochia trail. Image credit: Phil Westra, Colorado State University.
Integrated Weed Management Strategies for Control
Focusing on control of emerged seedlings prior to planting through strategic shallow-tillage (e.g. Undercutter/V-blade) to remove germinated seedlings where acceptable can help manage early emerging kochia.
Establishing competitive crops using optimum planting dates, row spacing, seeding rates, and competitive varieties that close their canopy faster can help crops to compete with kochia, especially during early critical weed free periods.
Establishing competitive crops such as winter wheat has been shown to reduce kochia biomass in field studies by over 99% compared to treatments without wheat. Mowing kochia closer to flowering has been shown to reduce seed densities the following year by 98% and reduce biomass by 33% compared to a non-mowed control in a surface mining reclamation project.
Chemical fallow is commonly used in the high plains, however the development of herbicide-resistance to commonly used fallow herbicides allows for maximum kochia growth and seed production in the absence of plant competition.
Fall-sown cover crops can compete with both late-fall and early-spring emerging kochia to help minimize kochia growth and biomass production. Fall-sown triticale has been shown to reduce kochia densities by 78 to 94% and biomass by 98% compared with kochia in chemical fallow.
Because kochia and spring-planted cover crops both germinate at the same time in early spring, spring-planted cover crops are not effective at reducing kochia densities or biomass. This emphasizes the value of fall-sown cover crops for kochia suppression. Fall-sown cover crops that produce the most biomass are most effective at suppressing kochia.
Early spring tillage prior to crop planting provides good control of early emerging seedlings. Less intensive, shallower ridge tillage has been shown to increase kochia densities up to 50 fold, which can be used to promote spring germination and emergence for subsequent control.
If herbicide resistance becomes a major issue in a given field, strategic deep tillage (e.g. moldboard plowing) (> every five years) can help reduce population numbers by inverting the soil and burying kochia to a depth where it is no longer able to germinate or remain viable (since average viability is two years).
Kochia has evolved resistance to several different herbicide modes of action (MOAs) (resistance to multiple MOAs within populations has been documented) which limits the use of those herbicide groups on certain populations. It is necessary to know if resistance to certain MOAs is present in a given population to formulate a successful herbicide program.
Chemical-fallow control of kochia is often where herbicide resistance, especially to glyphosate, is observed. Herbicide resistant populations are readily visible, with meandering trails of individuals (resistant progeny seed dropped as the parent plant tumbles across a field in the fall) surviving chemical applications in fallow fields.
Whether entering a fallow or cropping rotation, starting clean by removing weeds and planting into weed-free fields is critical to minimize weed competition for resources. Burndown products that contain glyphosate (RoundUp), glufosinate (Liberty), or paraquat (Gramoxone) are effective at controlling smaller emerged kochia prior to planting or entering a fallow period. Diversifying weed management strategies for kochia are essential to preserve and extend the longevity of currently effective chemical control methods.
Within crops there are many PRE and POST herbicide options available for kochia control, however, herbicide resistance present at the field level will dictate efficacy of these products. Herbicide applications to kochia should be avoided during the early button stage due to dense leaf hairs that can reduce foliar adsorption. Reducing seed germination with PRE herbicides, as well as targeting smaller, more vulnerable kochia seedlings, should be the focus of chemical control programs.
There are currently no biological control agents for kochia. Kochia is so ubiquitous that biological control is not a realistic option.
Kochia Resources and References
Friesen LF, Beckie HJ, Warwick SI, & Van Acker RC (2009) The biology of Canadian weeds. 138. Kochia scoparia (L.) Schrad. Canadian Journal of Plant Science 89:141-167
Kumar V, Engel RP, Currie R, Jha P, Stahlman PW, Thompson C (2019) Dicamba-resistant kochia (Bassia scoparia) in Kansas: characterization and management with fall-or spring-applied PRE herbicides. Weed Technology 33:342-348
Kumar V, Jha P, Jugulam M, Yadav R, Stahlman PW (2019) Herbicide-resistant kochia (Bassia scoparia) in North America: a review. Weed Science 67:4-15
Kumar V, Jha P, Lim CA, Stahlman PW (2018). Differential germination characteristics of Dicamba-Resistant Kochia (Bassia scoparia) populations in response to temperature. Weed Science 66:721-728
Loux M, Stachler J, Johnson B, Nice G, Davis V, Nordby D (2006) Biology and management of horseweed. The Glyphosate, Weeds, and Crops Series. GWC-9. Accessed online at https://www.extension.purdue.edu/extmedia/GWC/GWC-9-W.pdf on January, 2020
Menalled F, Smith R (2007) Competitiveness of herbicide-resistant and herbicide-susceptible kochia (Kochia scoparia (L. Schrad.) under contrasting management practises. Weed Biology and Management 7:115-119
Mesbah A, Nilahyane A, Ghimire B, Beck L, Ghimire R (2019). Efficacy of cover crops on weed suppression, wheat yield, and water conservation in winter wheat–sorghum–fallow. Crop Science 59:1745-1752
Mosqueda EG, Lim CA, Sbatella GM, Jha P, Lawrence NC, Kniss AR (2020) Effect of crop canopy and herbicide application on kochia (Bassia scoparia) density and seed production. Weed Science 68: 278-284
Petrosino JS, Dille JA, Holman JD, Roozeboom KL (2015) Kochia suppression with cover crops in southwestern Kansas. Crop, Forage & Turfgrass Management 1:1-8
Schwinghamer TD, Van Acker RC (2008). Emergence timing and persistence of kochia (Kochia scoparia). Weed Science 561:37-41
Wali MK (1987) Mowing of annual colonizers to enhance revegetation after surface mining. Reclamation and Revegetation Research 6:157-161
Weatherspoon DM, & Schweizer EE (1971). Competition between sugarbeets and five densities of kochia. Weed Science 19:125-128
Wilson RG (1993). Effect of preplant tillage, post-plant cultivation, and herbicides on weed density in corn (Zea mays). Weed Technology 1:728-734