What makes foxtail barley hard to kill?
With hairy and extremely narrow leaves, it’s difficult to get good herbicide coverage on foxtail barley. As it’s a perennial, the dead leaves from the past season cover the growing shoots in spring, reducing contact potential. If plants escape a pre-seed or pre-emerge application, there are limited in-crop products available. In broadleaf crops (aside from glyphosate tolerant crops), quizalofop is the only option. Fall is the optimal time to spray, but efficacy is greatly influenced by environmental conditions. If there are fall rains, it’s likely that foxtail barley is actively growing and the herbicide can be translocated to the roots. Temperatures also need to be above 10 degrees Celsius for optimal uptake. If there is no moisture or the temperatures are cooler, the plants go dormant reducing control. Each season that passes without adequate control, increasingly higher herbicide rates are needed to get an effective kill
Why glyphosate alone isn’t always effective.
Getting good contact on foxtail barley with glyphosate can be a struggle. Typically, glyphosate is applied with low water rates which isn’t conducive for contact on the small leaves. The size of the plant also dictates that rate of glyphosate that is needed. Underdosing may suppress a weed for period of time but will not provide control.
- Seedlings with crowns less than 1″ or shorter than 3″ will be controlled at 0.33L/ac (180g ai)
- Mature and stressed plants require 0.67-1.33L/ac (540-720g ai/ac) depending on the conditions and size.
Actives that control or have some activity on foxtail barley include:
- Group 1: quizalofop (Assure II, Yuma, Leopard, etc.)
- Group 2: propoxycarbazone-sodium (Olympus), flucarbazone* (Inferno Duo, Everest)
- Group 3: propyzamide (Kerb SC)
- Group 9: glyphosate
- Group 15: pyroxasulfone* (Focus)
It should be noted that with the chemicals listed above, there are limitations to the recommended dose rate and the size of weed they will kill.
What products should I tank mix?
It’s not a registered tank mix, but combining quizalofop with glyphosate can improve control. Olympus controls foxtail barley plants prior to emergence, but is not effective on established plants. For wheat pre-seed applications, Inferno Duo can be added to glyphosate to control emerged seedlings. Another potential pre-seed tank mix is AMS. A 3 year study in the United States found that tank-mixing AMS with glyphosate improved efficacy on established foxtail barley plants.
Other ways to reduce my foxtail barley populations?
- Targeted cultivation of patches.
- If in a saline area, a salt tolerant forage can be seeded (foxtail barley is not competitive).
- Increasing seeding rates and banding nitrogen to raise crop competition.