MANKATO, Minn. – As the new Liberty Link GT27 soybean variety enters the markets, with its traited tolerance to HPPD-type herbicides, there is still a great deal of uncertainty as to how this new technology can be used.
The Minnesota Soybean Growers Association is recommending farmers proceed with caution.
“Our concern has nothing to do with the viability of the product, it is the confusion that is of concern,” said David Kee, Ph.D. and director of research at Minnesota Soybean, during a phone interview. “We want to implement this technology, but we want it implemented correctly.”
The Liberty Link GT27 (LLGT27) seed variety has the standard tolerance to glufosinate and glyphosate-based herbicides, Liberty and Round Up.
The new genetics behind LLGT27 is that it is also traited to be tolerate of HPPD (Group 27) based herbicides. Balance, Callisto, Laudis are examples for corn. Potentially, these genetics could be a very useful tool for farmers in need of additional modes of action to control weeds in the soybean fields.
“But we have not had and do not have any HPPD chemical product labeled for use over soybeans, any kind of soybeans,” said Kee. “So, you have got half a solution.”
Without that legal herbicide, growers will be purchasing a trait they cannot directly use. They can still take full advantage of the Liberty or Round Up tolerance trait, but there are no HPPD chemicals that can legally be applied to soybeans.
The argument for LLGT27 soybeans has been made that the trait is an insurance policy against drift. Should a beanfield get hit with Callisto from a nearby corn field application, these beans might survive.
The other possible benefit to growers is, for example, a grower applied Callisto or other HPPD herbicide to a field as a pre-emerge ahead of corn planting. Then, due to weather or another reason, decided to plant soybean in that field. The LLGT27 variety would have a better chance at survival in that field. However, this results in another problem.
“Right now, because we don't have an HPPD compound labeled for use in soybeans, the maximum residue level is zero,” he said. “So, any HPPD that shows up in soybean grain is now above the maximum residue level.”
The EPA determines how much residual chemical is allow in a harvested crop based on the chemicals that are labeled to be applied to that crop legally. Without a labeled HPPD chemical for soybeans, EPA will not accept information to determine a maximum residue level. Therefore any HPPD found in harvested soybeans would be over the maximum residue level of zero.
“Any residue level that pops up becomes contaminated grain,” he said. “The farmer is supposed to destroy the contaminated grain.”
Should that grain go into an elevator and be mixed with other grain, all that grain is contaminated and must be destroyed. If the grain gets on to rail cars, that shipment must be destroyed.
Worse yet, should the grain make it into a shipping container on a ship bound for export – if it tests positive for residual HPPD at the foreign market – that creates a mess of trade issues.
Adding to the confusion surrounding LLGT27, there are several different chemicals listed as HPPD-inhibitors. Isoxoflutole, the active ingredient in Balance, Mesotrione in Callisto, Tembotrione in Laudis, and Topramexone in Impact are the main chemicals. There is also Pyrasulfotole.
“We have no information about the impact of Pyrasulfotole, which is usually mixed with other materials and maybe the other material will kill soybeans,” said Kee. “There is some missing data that we need get collected and out to the growers.”
The early data on LLGT27 shows very strong tolerance to the Isoxoflutole compound. The soybean’s tolerance of the other HPPD herbicides is more mixed with different chemicals having varying degrees of impact on the plants.
“The tolerance is specifically for Isoxoflutole, so one of five,” he said.
The comments from the Minnesota Soybean Growers Association are not to discourage growers away from the new LLGT27 technology, but to encourage caution. The goal is to see the technology implemented correctly and successfully.
As of now, the genetics have been put ahead of the chemistry. There are still obstacles in chemical labeling that must be overcome. Further testing, data collection and presenting that data to the growers needs to be completed to ensure growers implement the technology well.
Kee encourages any growers that have decided to plant the LLGT27, HPPD tolerant soybean variety to treat it as if it were HPPD intolerant. Take advantage of the Liberty Link technology like any other similar soybean variety, but completely ignore the HPPD trait. Also, take caution to avoid any potential residuals in the harvested grain, he concluded.