Looking for glyphosate alternatives?

Date:12-09-2022

If you’re waiting until spring to get your glyphosate for the coming growing season, Dwight Lingenfelter, Extension weed scientist at Penn State, thinks you should be in luck.

″From what I’m gathering … it doesn’t seem to be as grim as we were talking about last year, so we hope that holds true,″ he said during a recent crops conference in Grantville, Pa.

Still, as 2022 showed, anything can happen, so it’s better to be ready with a backup plan in case supplies of Roundup, or other beneficial herbicides, dry up.

Lingenfelter spent part of the past growing season testing alternative herbicide combos that didn’t have glyphosate, or had lower amounts of glyphosate in them. It wasn’t a replicated trial that he hopes to get published, but rather a basic test of how different herbicide combinations did under what he describes as ″the worst-case″ conditions: small strips of fallow ground with no other crops growing and no other cultural practices.

In the burndown, dozens of plots at the Penn State research farms in Rock Springs and Landisville were sprayed on April 30. Weeds such as marestail, mouse-ear chickweeds, dandelions, annual bluegrass and broadleaf plantains had already emerged. Spray volumes were 15 gallons an acre with MSO and AMS adjuvants added.

The postemergence field tests were sprayed June 13-14.

What did Lingenfelter find? Here’s some results that you might want to keep handy:

Burndown winners

The trio of paraquat (Gramoxone SL) with 2,4-D and metribuzin (or atrazine for corn only) provided the best non-glyphosate control for cereal rye burndown, Lingenfelter said. It also provided adequate control for marestail shorter than 6 inches. But it provided little perennial weed control, and almost no control of tall marestail or annual ryegrass. Also, keep in mind that special training is required when using paraquat.

Basis Blend with metribuzin, Sharpen and 2,4-D provided good foliar and residual marestail control, and good initial control of waterhemp. It provided a burndown and some residual in one pass. But he recommends applying 0.825-2.5 ounces an acre in corn, or 0.825 ounces in soybeans at least 15 days before planting. There is also a risk of corn injury under cool, wet conditions, especially when using 2.5 ounces near corn at planting time.

The combination of Acuron and atrazine, which can only be used in corn, provided good control of winter and summer annuals, and you can add more atrazine or 2,4-D in the mix. But it doesn’t provide much control for cereal rye or ryegrass, so paraquat could also be included to enhance burndown control.

Sharpen with a lower rate of glyphosate (1/2X to 2/3X rate per acre) and 2,4-D provided good burndown of cereal rye and other cover crops, as well as good control of marestail and fair control of other weeds because of the lower glyphosate rate. But it didn’t do as well as on large weeds.

Read more at American Agriculturist.