Several field trials were undertaken in 2017 to look at options for controlling herbicide-resistant kochia, Palmer amaranth, and waterhemp in dry bean, corn, and sugarbeet. In addition over 80 kochia, Palmer amaranth, and waterhemp plants were collected for testing of herbicide resistance. Of these 50% of kochia and 13% of Palmer amaranth plants tested were resistant to field rates of glyphosate. While options are limited in the Panhandle, pairing crop rotations with herbicide programs using PRE and layby treatments provided effective control of key weed species.
Figure 1. Aerial imagery was collected at bean emergence using a drone. All dark green rows correspond to plots with different rates of char (10, 20, 30, 40, and 60 tons/acre).
Figure 1. Downy brome (cheatgrass) is greening up in a pasture in Scottsbluff County due to recent warmer temperatures; photo taken February 20, 2017. (Photo by Cody Creech)
Just a month after double-digit below zero temperatures, Nebraska hit an extended period of above normal temperatures, coaxing weed seeds to germinate early in many fields and pastures and creating the need to tackle the influx early.
Figure 1. Common pigweed species found in the Nebraska Panhandle. Palmer amaranth and waterhemp are ALS-resistant. Images, from top to bottom in each column, are of seed, seedlings, and plants in the vegetative growth stage. (Source Nebraska Extension EC94-138)
Palmer amaranth and waterhemp in the Panhandle are resistant to ALS-inhibiting herbicides. While control of these weeds in dry bean can be challenging, corn, irrigated small grains, and sugarbeet make good rotation options for control. A combined pre/post treatment strategy controls weeds in the early part of the season when crop yield is most impacted and weed species are most susceptible to control inputs.
The development and management of pesticide-resistant kochia in dryland and irrigated systems in the Panhandle including a table of herbicide options for Nebraska.
Figure 2. Cheatgrass seed heads (or panicles) as they mature. The panicles on the left are shattering, the second on the left is mature but not shattering, the two on the right are immature.
The winter annual weed species cheatgrass is competitive with crops, desirable forage, and native plants and will reduce productivity of crop and range land. Learn how grazing, mowing, and properly timed herbicide application can be integrated to provide effective control.
Weed management is a long-term battle that needs to continue even in tight margin years.Although herbicide costs may seem prohibitive, it’s important to consider the long-term implications of limiting or eliminating the use of herbicides in crop production systems.Weeds left unmanaged after wheat harvest use valuable nutrients and water needed for the following year’s crop while producing seeds to replenish the soil seed bank.
