Application time of day affects PPO control of Palmer pigweed

Palmer pigweedThe time of day when Liberty herbicide is applied can affect its effectiveness on Palmer amaranth, according to University of Tennessee studies.

But researchers also have found that time of day can affect the efficacy of PPO herbicides, such as Flexstar, prefix, Ultra Blazer and Cobra, used on Palmer amaranth.

The project examined herbicide applications at sunrise, noon and sunset on 3- to 6-inch-tall Palmer amaranth. The herbicides involved were Flexstar, Cobra, Ultra Blazer, Resource, Cheetah (glufosinate) and Cheetah Max (glufosiinate and fomesafen premix).

As with earlier trials using Liberty, the researchers say the same effect with Cheetah. Palmer amaranth control was significantly reduced with sunrise and sunset applications compared to noon applications.

The researchers saw similar, although less drastic, results with the PPO herbicides.

Noon applications resulted in 10 to 15 percent better Palmer amaranth control than sunrise applications and 5 to 10 percent better than sunset applications.

The researchers also noted significant injury of 15 to 25 percent from each herbicide.

Read more about the project at the University of Tennessee.

View a video about their research on YouTube.

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