by Dwight Lingenfelter

Some often wonder why there have not been any new herbicide modes of action registered in the past decade or so.

In fact, it has been more than 30 years since the last unique herbicide MOA (HPPD/group 27) was introduced to the U.S. market.

Since then, several new herbicide active ingredients within already existing MOAs — and many new premixed or revised formulations of older active ingredients — have been brought to market. Unfortunately, these “new” products and trade names cause confusion because many assume these are something novel and different.

Furthermore, there continues to be more generic or post-patent products on the market, which adds to the confusion. As usual, there is no easy answer as to why there are no new MOAs, but here are some things to understand about the process and why we still don’t have new herbicide MOAs on the horizon:

It is hard to do. It is getting more difficult to discover new and unique molecules with herbicidal activity. It is estimated that for every 150,000 molecules analyzed for pesticidal properties, only one may have the potential to be taken to the next stage of development. And the success rate of it at each testing stage continues to dwindle.

Testing is rigorous. Any potential herbicide MOA candidate must pass a battery of toxicological, environmental and field-scale testing that can take at least 10 years or more before it can be launched commercially.

So, if a viable molecule was discovered this year, it would not be available for farmers to use until at least 2035. At any stage, the active ingredient could be abandoned because of negative characteristics.

From the development of an herbicide to its use in the field, many federal laws — such as the Federal Insecticide, Fungicide and Rodenticide Act, and the Federal Food, Drug and Cosmetic Act — must be adhered to, and agencies such as USDA, the Food and Drug Administration, and EPA will also get involved to ensure its safe use — and human, animal and environmental welfare.

More recently, the Endangered Species Act has started playing a major role in the registration or re-registration of all pesticides.

It must be practical to use. The molecule must target weeds, but it must also be safe to use on crops such as corn, soybeans, wheat and cotton.

Since most companies recoup their investment costs on volume of sales, these types of large-acreage crops are targeted first. If by chance an herbicide is safe on specialty crops, it can be added to the label later — if it passes the rigorous testing parameters, and if the manufacturer determines it’s worth the investment to do so.

Simultaneously, the chemical must control a variety of weeds, especially driver species such as Palmer amaranth, waterhemp, horseweed, ragweed, annual grasses or resistant species that are economically important. If it only controls a small spectrum of weeds that are not considered problematic, then it could be discarded or archived for future development.

Also, the molecule must be realistically formulated into a product that can be economically manufactured, and easily handled and used by applicators.

It costs a lot of money. It is estimated that it costs between $250 million and $300 million to bring an herbicide product to market. Agricultural companies need to prioritize what to invest in. Within the past 20 years or so, some of the major manufacturing companies have invested heavily in biotechnology that can be paired with existing herbicide chemistries, but less into pesticide discovery.

A few of these biotech outputs have included Roundup Ready crops, and XtendFlex and Enlist E3 soybeans. Furthermore, less funding for innovative herbicide discovery and research is available.  

Recently, companies that primarily sell generic or post-patent pesticides have been competing for herbicide market dollars. Since they don’t have the initial investment of developing a new active ingredient, they can be profitable more quickly by selling off-patent compounds. Thus, it can negatively affect companies that are more involved in pesticide discovery and research.

As consolidation of major manufacturers continues, fewer molecules will be able to be screened for their potential utility because fewer labs will be involved.

There are many other issues that need to be considered, including overall market research and return on investment; patent reviews and length (usually about 20 years from discovery); federal and state regulatory compliance; label writing and compilation; herbicide product formulation; product manufacturing facilities; and re-registration every 10 years.

It’s no wonder there are very few new herbicide MOAs coming to your field anytime soon. However, there are still several companies that continue to work on innovating new herbicides to combat the problem weeds we have.

Let’s hope they keep up.

Lingenfelter is an Extension associate of weed science with Penn State Cooperative Extension.