by: Cora Brott, UNL Agribusiness and Accounting Majors (Sophomore)
This blog is part of The Science Behind Dicamba Series from Dr. Andrea Basche’s course.
Recently a chemical, dicamba, used in farming has come under fire by not only farmers who grow crops that are not tolerant to dicamba, but also by the general public. Though dicamba is not a new herbicide and has been around for many years the recent backlash about the chemical has come after the release of dicamba-tolerant soybeans in 2017. As a result of the use of dicamba on these dicamba-tolerant soybeans came drift, volatilization, angry farmers, and public concern.
Soybeans in Daily Life
Soybeans are used in many products, including food for humans and animals and other products consumers buy everyday. Soy oil is most commonly used for human consumption, though other soybean products can be used as well. In particular, soymeal, the protein portion of soybeans, is used for animal consumption. Soybeans that are not used for human or animal consumption are used to make consumer products ranging from biodiesel to crayons. Consumer products made with soybeans are environmentally friendly because their composition is that of natural materials. In Nebraska, soybean production generated nearly $3 billion in 2015 and 2016, making soybeans the second largest cash crop in the state of Nebraska after corn. The expected planting of soybeans in Nebraska for 2018 is 5.90 million acres, which is a little over 20% of Nebraska cropland acres.
Dicamba and Restricted Use Pesticides
Dicamba, a restricted use pesticide (RUP), used in corn and soybeans is a hot topic in the agriculture industry because of increased use in soybeans in 2017. Dicamba became a RUP in 2018 because of its high rate of volatility, and susceptibility to particle drift, as well as, its extreme effectiveness at inhibiting cell division in plants which can cause severe damage to non-dicamaba-tolerant plants that caused several off-target issues in 2017. Because dicamba is a RUP, applicators must not only be certified public or private applicators, but they must also have special training on dicamba handling, application, and equipment cleaning after dicamba use; dicamba’s RUP classification also limits buyers to certified personnel only.
Dicamba Use in Nebraska in 2017
Dicamba’s use in Nebraska greatly increased in 2017 due to the availability of dicamba-tolerant soybeans. With the increased use of the dicamba on dicamba-tolerant soybeans, increased off-target dicamba movement has been reported. In Nebraska, 90 claims of off-target dicamba movement were reported to the Nebraska Department of Agriculture (NDA) in 2017. However, 348 claims were reported to Nebraska Extension Educators in 2017 that totaled 50,000 effected acres of non-dicamba-tolerant soybeans. Dicamba-tolerant soybean varieties showed 93% better weed control than non-dicamba-tolerant soybeans in the state of Nebraska.
Expected Dicamba Use in Nebraska in 2018
Dicamba’s ability to control weeds so successfully has encouraged farmers to plant more dicamba-tolerant soybeans with farmers across the United States anticipated to plant 52% of their soybean acres to dicamba-tolerant soybeans in 2018. Of the 52% of soybean acres planted to dicamba, farmers anticipate post-emergence, or after the plant has broken the soil’s surface, spraying will be around 88% of those acres. With expectations of increased use of dicamba-tolerant soybeans an increase in the use of dicamba can also be anticipated. The use of dicamba in 2018 can also expect to be monitored and controlled more closely by applicators. Such factors that will be monitored more closely in 2018 are wind speeds between 3mph and 10mph at boom height, or spraying height, maximum boom height of 24 inches, minimum downwind buffer zones of 110- to 220-feet depending on the crop, extremely- or ultra-course spray nozzles, application in proper humidity and temperature, proper monitoring of rain expectations, and irrigation schedules among many other spraying elements.
Why Dicamba-Tolerant Soybeans?
The rise in the use of dicamba-tolerant soybeans has come as many weeds, such as palmer amaranth, water hemp, and kochia have developed resistance to other herbicides. Palmer amaranth, one of many weeds that effects soybean fields, has developed resistance to several different sites of action, or processes that are disrupted by herbicide use. Palmer amaranth is not the only weed that has developed resistance, in fact many weeds have developed resistance to the frequently used herbicide glyphosate, commonly known as Roundup. Because of weeds’ ability to develop resistance, herbicides, like dicamba, allow farmers to control weeds in their fields that have dicamba-tolerant crops.
The use of dicamba is a controversial topic that will continue to be monitored, discussed, and evolved. Changes to the labels, applicators’ list, and training by the Department of Agriculture are intended to ensure the safe usage of dicamba. The Nebraska Department of Agriculture makes reporting dicamba misuse simple by allowing reports to be formal complaints or anonymous tips. Additional information about dicabma can be found on university extension websites.