Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
For no-till fields, a non-selective herbicide needs to be used prior to planting. If grasses or perennial weeds are present, glyphosate is a better choice than paraquat. Fields worked with a vertical tillage implement for residue management still need a non-selective herbicide. These implements are not weed control tools.
There are few effective herbicides labeled for preemergence applications. Sharpen is labeled but we have limited data in the region. Valor can be used at 1 to 2 oz with the burndown application, but there must be a 7 day period between application and planting wheat. Valor is not labeled for barley.
Axiom and Prowl H2O can be used at crop emergence (Axiom at the spike stage and Prowl H2O at 1 leaf stage, winter wheat only). Neither provides control of emerged weeds but can have utility in situations of needing limited residual control shortly after planting.
Products that provide postemergence control include: Harmony, Harmony Extra, Starane Ultra, Osprey, PowerFlex, Axial XL, or 2,4-D. Other labeled herbicides with a limited fit include Finesse and Maverick.
Control of annual ryegrass has been good with Opsrey, PowerFlex, or Axial XL. However, ALS-resistant ryegrass has been identified in Delaware and these populations will not be controlled by Osprey or PowerFlex. Furthermore, Finesse will not control these populations. In situations where ALS resistance is suspected, Axial XL is the best postemergence option.
ALS-resistant common chickweed has been confirmed in Delaware. These biotypes are not controlled with Harmony Extra, Osprey, PowerFlex or Finesse. Currently, Starane Ultra has showed the best activity, often not killing common chickweed, but providing good suppression. Starane Ultra can be used either in the fall or spring.
