To help growers decide how to respond, researchers recently studied two new dicamba-resistant populations in Kansas. The weeds were found in fallow fields that were part of a wheat-sorghum-fallow rotation.

The research team compared both spring and fall applications of two preemergence herbicide tank mixtures with multiple sites of action. One mixture contained dicamba, pendimethalin and sulfentrazone, while the other contained metribuzin and sulfentrazone.

While both mixtures provided effective control of dicamba-resistant kochia when applied to fallow fields, spring-applied herbicides provided better extended control. In fact, spring applications reduced emergence by 85 to 95 percent over three to four months.

The bottom line: To control kochia and sustain the long-term utility of dicamba, adopt an integrated management strategy that includes preemergence herbicide mixtures with multiple sites of action. And remember, a single kochia plant has the potential to produce as many as 100,000 seeds. If left uncontrolled, mature plants can break off at their base and become “tumbleweeds” – dispersing seeds as they are blown along by the wind. Early intervention is a must!

Want to know more? Read the article, “Dicamba-Resistant Kochia (Bassia scoparia) in Kansas: Characterization and Management with Fall- or Spring-Applied Preemergence Herbicides” found in Volume 33, Issue 2 of the journal Weed Technology.