From Weekly Crop Update
Mark VanGessel, Extension Weed Specialist; firstname.lastname@example.org
Some fields were sprayed last spring with Osprey for control of annual ryegrass and there was no control. At least one of these fields was confirmed as having ALS-resistant annual ryegrass. If Osprey or PowerFlex (another ALS-herbicide or Group 2 herbicide), were used for annual ryegrass but did not control them, Axial XL is the only option for ryegrass control this spring.
More fields with ALS-resistant common chickweed (resistant to Finesse, Harmony Extra, Osprey, and PowerFlex) are showing up in Delaware. Spring application of Starane Ultra is the best option to suppress/control the resistant chickweed.
Be sure to read the herbicide label carefully because some products can be tankmixed with nitrogen but only if the nitrogen is no more than 50% of the spray solution (nitrogen is mixed 1:1 with water). A few specifics:
- Osprey cannot be applied within 14 days of nitrogen application
- Harmony Extra can be applied with nitrogen, but use of surfactant differs depending on concentration of nitrogen and targeted weed species
- Axial XL and PowerFlex can only be applied with nitrogen if it is mixed 1:1 with water; also PowerFlex cannot be applied with nitrogen if the amount is more than 30 lbs of N/A
Read the label for rotational restrictions. Axial XL and PowerFlex are two herbicides that are effective on annual ryegrass. Both of these can be double-cropped with soybeans. However, PowerFlex will injure vegetables planted after harvest. There is a 90 day rotational restriction with Axial XL for soybeans and most vegetables. Starane Ultra has a 120 day restriction for replanting crops (Delaware has a label for planting soybeans 90 days after application, but Maryland does not have this special label).