Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
This fall has presented an opportune time to treat small grains with a postemergence herbicide. For small grains planted in September and early October, I like spraying them in the fall rather than waiting until the spring. These herbicide applications have been more consistent and overall better weed control than spring treatments in our trials. The soil temperature remains warm for weeks after the first frost and this keeps the weeds in an active state. I find annual bluegrass, henbit, or speedwells species are often more susceptible if treated in the fall compared to early spring. Once we have consistently cold weather and soil temperatures drop, then fall treatments will be questionable. Fields may need a spring herbicide application for wild garlic control, but often broadleaf weed control is excellent with fall treatments and additional treatments are not needed.
A few considerations
Fall herbicides are particularly important if the field was not “clean” at planting. Use of a vertical tillage tool often will not kill weed seedlings, and they recover and can be too large for effective control in the spring.
Zidua or Anthem Flex are only effective on seedlings as they emerge from the soil. They have little to no effect on emerged plants. I am not sure they have a lot of value when applied this late in the fall.
If bluegrass is an issue, Osprey is the best product available. Italian ryegrass can be controlled with Axial products, Osprey or PowerFlex. Do not apply nitrogen within 14 days of Osprey application. (Note Osprey or PowerFlex are not safe on barley)
For late planted small grains:
- Be sure to observe the size requirement before application.
- Harmony Extra, Quelex, and Starane should not be applied before the two-leaf stage of wheat.
- Also leaves of late planted wheat may be tender, use caution when selecting the adjuvants.