Roundup (Glyphosate) Alternatives

 

Roundup (chemical name glyphosate) is the most commonly used herbicide in the world. However, due to weed resistance and human health concerns, its days may be numbered. How will farmers control weeds chemically if this product is gone? The following is a highly technical summary of herbicide alternatives to using Roundup (common name) or glyphosate.

One reason glyphosate was so popular was because crops like corn and soybeans were inserted with genetically modified genes that allowed the plant to survive the chemical application. Several crops now have genetically modified genes for various herbicides. The problem is that none are quite as good as glyphosate, either due to performance or lower cost. However, there are some options.

Burndown chemicals are used at the beginning of the growing season to kill the first flush of weeds. Weeds compete with the main grain crop for moisture and nutrients. Killing weeds early is the best strategy. However, often cool soil and air temperatures and excess moisture can prevent farmers from getting the weeds killed on time.

The following is a list of burndown herbicides that are alternatives to Glyphosate. Sharpen (saflufenacil) can be used in soybeans to burn down small growing broadleaf weeds, especially marestail, pigweed, and horseweed. It’s fast-acting but is not as good on grassy weeds. Glyphosate is really good on most grass weeds, so the two were often combined.

Another herbicide, 2-4D Ester, is also used on soybeans as a burndown to control broadleaves and is especially effective on marestail. Farmers have to be careful with 2-4D because it can drift and cause damage to other crops and is toxic to fish and aquatic invertebrates. This is an old chemical that has been around since the 1940s. It needs to be applied before planting, and the waiting period before planting is typically 7-14 days. Rainfall often shortens the waiting time; however, always follow the label.

In corn, Atrazine (common and chemical name) is a restricted-use herbicide, meaning farmers need to be licensed to apply it. Atrazine can be used as a burndown to kill small broadleaf leaves plus some grasses. It has residual soil activity (long-lasting) but has some environmental concerns regarding groundwater contamination.

Gramaxone (paraquat) is a highly effective, restricted-use chemical that kills almost all vegetation. It’s a desiccant (absorbs moisture) and hard on plants, equipment, and people if you come in contact with it. It burns all top growth immediately but does not hurt the roots. It is good on Palmer Amaranth and barnyard grass, especially. It has zero residual activity and is best applied in warm sunny conditions. It can be used as a quick burndown before planting most crops.

Zidua (Pyroxsulfone) can be used on corn and soybeans and has long-lasting residual control. It controls Palmer amaranth and water hemp effectively. However, it needs to be incorporated into the soil and needs adequate rainfall (0.5 inches) or soil moisture to kill weeds as they emerge. The problem is that it is expensive (at least $8-$16 per acre just for Zidua), and timing is critical. Prices vary.

Another burndown is Anthem Maxx/Flex (Pyroxsulfone + Fluthiacet-methyl), which can be used in both corn and soybeans. This herbicide needs a minimum of 10 gallons of water, up to 40 gallons in dense vegetation. This product is often used to control glyphosate-resistant or ALS-resistant weeds and is fairly good on Palmer amaranth, water hemp, and many other weeds as long as the weeds are small. It also may cause some crop injury if used at high rates.

A burndown chemical to avoid is Liberty (glufosinate), which controls a wide variety of weeds post-emergence but requires good growing conditions (warm, sunny), which seldom occur with spring weather. Liberty is really good for post-emergence weed control after the crop is up. Surtain (Saflufenacil + Pyroxasulfone) is another combination herbicide that can be used on corn and has long residual activity but is not considered a burndown. It is applied three weeks before planting and is good on water hemp and grasses.

If glyphosate cannot be used, some of the other herbicide chemistry will be used more frequently to control grasses. Sencor, Valent, Glory, Matador, Boundary, Tricor, Lexone, etc. are Group 5 herbicides that inhibit photosynthetic activity and contain Metribuzin, which can be used in corn and some soybean varieties. Crop injury may occur with Metribuzin sometimes. Dual Magnum (Metolachlor) can be used pre-plant or post, and Select Max (clethodim) post-application can both be used to control annual grasses in corn and soybeans. Herbicide options without Roundup or glyphosate generally are more complicated and more expensive, but it can be done.