Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
The current weather is forcing us to do things different than we normally do. One issue to keep in mind is the herbicide and nitrogen restrictions. 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.
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 are reports of fields with poor chickweed control due to resistance to Harmony, Harmony Extra, or Finesse. If you are in that situation your alternatives are quite limited. Other small grain herbicides that we are familiar with do not provide acceptable chickweed control. One product to suggest is Starane Ultra (from Dow AgroSciences). This product is labeled for wheat and barley and has been used in the western US for control of Group 2 resistant weeds. Local data is limited, but in our trials it has good crop safety and good chickweed control. However, it will not control other key species such as wild garlic. Starane Ultra can be tankmixed with Harmony Extra to broaden the spectrum of control. Starane Utra by itself does not need an adjuvant and can be applied in nitrogen. Be sure to read and follow label directions.
Finally, some reminders on timing restrictions for small grain herbicides — the timing restrictions are based on crop safety.
2,4-D: up to jointing stage (pre-jointing)
Banvel/Clarity: up to jointing stage (pre-jointing)
Osprey: up to jointing stage
Buctril: up to boot stage
Harmony Extra or Harmony GT: up to flag stage (pre-flag leaf)
Starane Ultra: up to flag leaf emergence
PowerFlex: jointing
Axial XL: prior to boot
Tags: 18:1, barley, small grain weed control, wheat