Sorghum, whether for grain or silage, is becoming a popular option for Northeast growers — especially as a last-minute emergency forage for dairy farms.

And while it may look like corn — especially early — it has a lot of nuances growers unfamiliar with it should be aware of, such as the proper use of herbicides to control weeds.

“We’re getting more and more questions about weed control in sorghum, whether grain or forage, since it’s been around for a long time but hasn’t been in lots of acres around here,” says Dwight Lingenfelter, Extension associate of weed science at Penn State.

One thing that was clear during this year’s weed trials at the Rock Springs research farm near Penn State: Make sure your sorghum seed is coated with a seed safener.

Lingenfelter says that he assumed the sorghum seed he got from the company participating in the trial was coated with either a safener or something else to protect it from herbicide injury. But the results from the trial showed otherwise. Fields that should have been packed with growing sorghum plants had skips all over the place, and plots where plant emergence occurred were filled with weeds.

“We found stunting, missing plants and, in most cases, 35% to 45% injury compared to the other untreated check right next to it, which was 12 to 15 inches tall,” he says. “The tested ones were 8 to 10 inches tall. It shows the difference and why we treat seed.”

So, how did this happen? Since it was a fairly small trial, Lingenfelter believes it was just a bag of seeds that was skipped over or missed during the process of applying safener. Most seed manufacturers will apply safener at the plant before it is shipped out for sale or to a farm, he points out. But not always.

The label on the seed bag should indicate that a safener has been applied, Lingenfelter notes. If you have a question or a concern, check with the seed dealer to see if it has been done. Screen and Concep, the most common seed safeners, are off patent and are widely available for a grower to purchase and use.

EVALUATING HERBICIDES: Seed industry reps tour the Penn State weed trials in Rock Springs. The trials compare various herbicides and formulations for pre- and postemergence weed control. Mixes of three to four different products, up to a maximum of six, were compared to a control plot with no herbicide applied.

Of particular concern, he says, are the shoot-growth inhibitors — or Group 15 products — that are soil-applied and help to control grass weeds and short broadleaf weeds.

“Some herbicides can cause injury if you don’t have the proper requirement of the seed,” Lingenfelter says. “There are certain herbicides, mainly the Group 15 herbicides, things like metolachlor and Dual, for example, and that’s when we need to make sure the seed is treated with a safe safener or antidote.”

Corn and soybean trials

The sorghum herbicide trial is part of the larger herbicide formulation trial that focuses mostly on corn and soybeans.

The trials compare various herbicides and formulations for pre- and postemergence weed control. Mixes of three to four different products, up to a maximum of six, were compared to a control plot with no herbicide applied.

Lingenfelter says that this year’s early drought showed the importance of considering a true two-pass herbicide program on your operation. Soil-applied residual herbicides need at least a half-inch to 1 inch of rain to activate as this helps to incorporate the herbicide down into the zone where seeds are germinating. Across the region, this spring was one of the driest on record.

“Because of that, if we just had strictly a preemergence herbicide program, we were getting anywhere between 60[%] and 70% control and that was it, and the weeds are continuing to grow from there,” he says.

Early results showed that the best weed control, across the board, was with a preemergence residual placed early, followed by a second pass to control escapes. “And some of those programs will benefit from the rains over the past couple of weeks,” Lingenfelter says.

Old is new

Like in past years, the trials tested older and newer herbicide formulations.

“We’re going now on over 30 years without a true or unique mode of action,” Lingenfelter says. “And the reality is, some companies are going back to the shelf looking at older products and mixing them with relatively new products.”

One example is Perpetuo from Valent. It is a mix of Zidua, or Anthem, mixed with an herbicide from 25 years ago, Resource, that is similar to the mode of action provided by Cadet, or Aim. Another product, Lorox, which Lingenfelter says has been available for 50-plus years, is starting to see some newfound utility in soybeans.

The lack of new modes of action is a problem in both corn and soybeans. And while some companies have hinted at new stuff on the horizon, Lingenfelter says they will not be ready for market for likely some time.

“The problem that we’re dealing with is, even if we discovered that they came out with a new active ingredient or new mode of action today, we wouldn’t see it on the market until at least 10 years, or 12 years down the line,” he says. “What we have is what we have right now, and we have to use them judiciously.”

The full results of the trials will be released later this year.