Feral rye (Secale cereale L.), also commonly known as cereal or volunteer rye, is a troublesome winter annual grassy weed in wheat producing regions of the United States, including Kansas. Feral rye seeds can germinate in fall or early spring with optimum soil temperatures ranging from 55 to 60 °F. Feral rye generally matures early and shatters seeds before wheat harvest. A single feral rye plant can produce up to 800 seeds and those seeds can remain dormant and viable in soil for several years. The contamination of feral rye seeds can cause wheat dockage, losses in wheat quality, and grade reduction. The presence of feral rye seeds in wheat grains can also reduce the milling and baking characteristics of wheat flour. A survey conducted in 1995 estimated that the feral rye infestation in winter wheat was up to 600,466 acres in Kansas. The management of this winter annual has always been challenging in wheat, as current herbicides do not have the selectivity that allows for effective control without causing injury to wheat.
CoAXium® wheat production system
CoAXium® wheat production system is a new non-GMO herbicide-resistant wheat technology that combines the use of Aggressor® (quizalofop-p-ethyl, Group 1) herbicide with wheat varieties containing genes that confer tolerance to this herbicide – AXigen® trait. Three CoAXium® hard red winter wheat varieties (LCS Fusion AX, Crescent AX, and Incline AX) that contain the AXigen® trait (resistance to the ACCase class of herbicides) are now commercially available for use. Aggressor® herbicide has good foliar activity on grassy weeds, so the CoAXium® wheat production system can provide an opportunity for post-emergence control of feral rye in wheat.
On-farm field study
An on-farm field study near Great Bend, KS evaluated different rates and timings of Aggressor® herbicide for feral rye control in winter wheat during 2018/2019 growing season. The study utilized a CoAXium® winter wheat variety “LCS Fusion AX” planted on Nov. 19, 2018. The field site had a natural infestation of feral rye population. Treatments included post-emergence applications of Aggressor® herbicide in fall (3- to 4-leaf stage of wheat) and spring (3- to 4-tillers stage of wheat) at different rates: 8 + 8, 10, and 12 fl oz/a.
Results indicated that all Aggressor® treatments provided excellent late-season control of feral rye compared to non-treated plots irrespective of application timing and rates used (Table 1; Figure 1).
Table 1. Feral rye control with fall/spring-applied Aggressor® herbicide in LCS Fusion AX winter wheat at a grower field near Great Bend, KS in 2019.
|
Herbicide |
Rate |
Timing c |
Feral rye d |
||
|
4/18/19 |
5/2/19 |
6/6/19 |
|||
|
(oz/a) |
-----(% control)----- |
||||
|
Aggressor + NIS a |
10 |
FP |
89 ab |
94 ab |
96 a |
|
Aggressor + MSO b |
10 |
FP |
89 ab |
94 ab |
96 a |
|
Aggressor + MSO b |
10 |
SP |
75 c |
94 ab |
96 a |
|
Aggressor + MSO b |
12 |
SP |
80 bc |
93 ab |
94 a |
|
Aggressor + NIS a/ Aggressor + MSO b |
8 (Fall) + 8 (Spring) |
FP/SP |
93 a |
96 a |
98 a |
|
a Nonionic surfactant (NIS) at 0.25% v/v was included. b Methylated seed oil (MSO) at 1% v/v was included. c Fall Post (FP) was applied on Dec 19, 2018, Spring Post (SP) was applied on April 4, 2019. d Means within each column followed by same alphabet letters are not different based on Fisher’s protected LSD test at P<0.05. |
|||||
Figure 1. Visual response on May 2, 2019 of feral rye in CoAXium® wheat plots treated with Aggressor® herbicide in fall (A), spring (B), fall followed by spring (C), and non-treated weedy check (D). Photos by Rui Liu, K-State Research and Extension.
Greenhouse study
In a separate greenhouse study conducted at K-State Agricultural Research Center near Hays, KS, approximately 9 feral rye populations collected from wheat fields in central Kansas were completely killed with a field-use rate (8 fl oz/a) of Aggressor® herbicide plus MSO (1% v/v) at 21 days after treatment (Figure 2). Further studies are in progress to understand the effects of plant growth stage, environmental factors, and adjuvant systems on the efficacy of Aggressor® herbicide on Kansas feral rye populations.
Figure 2. Visual response of 3 Kansas feral rye populations treated with 8 fl oz/a rate of Aggressor herbicide at 21 DAT in a greenhouse at K-State Agricultural Research Center-Hays. Photo by Rui Liu, K-State Research and Extension.
Summary
These preliminary results indicate that Kansas feral rye populations are generally sensitive to Aggressor® herbicide and CoAXium® wheat production system can help Kansas wheat producers in managing this hard to control winter annual grassy weed. In addition to feral rye, Aggressor® herbicide can also provide good control of most other winter annual grasses (including ALS-resistant weed biotypes) such as downy brome, jointed goatgrass, Italian ryegrass, and volunteer cereals, but provides no broadleaf weed control. Aggressor® herbicide should be applied to actively growing wheat and grasses during periods when the high daily temperatures are expected to be 40 °F or higher the following week.
Important note: Do not apply Aggressor® to non-AX wheat varieties (including Clearfield® wheat) or wheat will be severely injured or killed.
Vipan Kumar, Weed Scientist, Agricultural Research Center – Hays
vkumar@ksu.edu
Rui Liu, Assistant Scientist, Agricultural Research Center – Hays
tabitha723@ksu.edu
Dallas Peterson, Weed Management Specialist
dpeterso@ksu.edu
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