As we move into the spring and begin planning for a successful 2020 cropping year, it's never too early to think about how to manage one of the most challenging weeds – Kochia. This weed causes problems for growers as far south as Texas, and as far north as North Dakota - and while this sounds like its an isolated problem weed, it has recently been confirmed in Western Iowa, and seems to be travelling further and further. Kochia has shown resistance to 4 different modes of action, and in some instances, resistant to multiple modes simultaneously.1
Let’s review why Kochia is such a problem and ways we can manage it.
Kochia has the ability to germinate in temperatures from 39° to 106° F, can produce thousands of seeds per plant, and can do so multiple times in one season – this is why it feels like controlling it is a never ending battle! Kochia grows quickly and can get as high as 6’, its leaves are small, fuzzy and gray green in color. Once it is fully grown, Kochia turns into a tumbleweed allowing seeds to easily disperse. For an overview of kochia, and how to spot it, check out the Colorado State University Extension office page here: http://bit.ly/2OJHn3H
It’s important to recognize what you're putting in the tank when controlling weeds, but especially when controlling kochia. This weed has been confirmed to be resistant to up to 4 different modes of action. The groups confirmed to be resistant are below along with commonly used actives within each:
- GROUP 2 – ALS herbicides
- GROUP 4 – 2,4-D and dicamba
- GROUP 5 – atrazine
- GROUP 9 – glyphosate
So, what's the secret to managing kochia? GET 'EM BEFORE THEY COME UP - it’s never too early to begin your herbicide program. In fact, spring applications reduced emergence by 85 to 95 percent over three to four months2. As mentioned above, kochia can emerge with soil temperatures as low as 39 degrees so you NEED to start early! While there are many ways to attack kochia, there are few things to keep in mind, regardless of your cropping system.
- GET 'EM BEFORE THEY COME UP - This is worth repeating! The easiest weed to control is one that never comes up! As kochia begins to mature it becomes much harder to kill in crops with limited effective options, so it is very important to get control at, or before planting.
- Always use multiple modes of action to help fight future weed resistances and to ensure full kill if the weed is tolerant/resistant to one of the actives in the tank.
- Always use the right rate and adjuvant for the job. It is critical that you are selecting the appropriate adjuvant for the herbicides you will be using. Choosing the wrong adjuvant can dramatically affect the efficacy on the targeted weed.
- ALWAYS read and follow labels to find the right rate and adjuvant for the chemistry you are using.
These same principles above can be applied to another tough to control weed – Waterhemp since many of the same soil residual herbicides are very effective at controlling it. Here are a couple of strategies I recommend by cropping system:
1 Kumar V, Jha P, Jugulam M, Yadav R, Stahlman PW. Herbicide-Resistant Kochia (Bassia scoparia) in North America: A Review. Weed Science. 2019;67(1):4-15. doi:10.1017/wsc.2018.72 Site: http://bit.ly/37c1U7m
2 Cambridge University Press. "New insights on the control of dicamba-resistant kochia." ScienceDaily. ScienceDaily, 15 May 2019. Site: http://bit.ly/31JBeK9