Continuing the Dicamba Discussion
Dicamba has certainly been the talk of the countryside with all the controversies it brings to the table. In a recent blog post, we reviewed how an Arkansas weed scientist perceives the risks and rewards of dicamba and the resistance issue we have on our hands. What else do we know about dicamba? How does it work?
Dicamba is nothing new to the market. In fact, it has been a part of weed management practices since 1962. Fast forward to 2016 when dicamba-tolerant soybeans were introduced to the market; also known as Round Up Ready 2 Xtend Soybeans. The ever-increasing number of resistant weeds made the release of dicamba-tolerant soybeans seem like the perfect fix.
Dicamba is classified as a growth regulator herbicide, also referred to as synthetic auxins or group 4 herbicides. This type of herbicide replicates the action of auxin. Auxin is a plant hormone that causes cell shoots to elongate and is part of the regulation of plant growth. According to Iowa State University Extension and Outreach, dicamba herbicides bind to the receptor for auxin and initiate transcription of genes involved in cell growth. While plants can closely regulate concentrations of auxin within cells, they lack this ability with dicamba herbicides. Presence of group 4 herbicides, like dicamba, in cells results in deregulation of numerous important processes, resulting in abnormal growth and/or plant death.
By now we know the big issue is how sensitive surrounding non-dicamba tolerant crops are and how far the applied product can move from the target area. Why is this the case? Dicamba herbicides effect targeted plants at a lower application rate than most other herbicides. For example, it takes 1% of the standard glyphosate use rate (0.75 lb/ac) to injure corn. Whereas 0.005% of the dicamba use rate (0.5 lb/A) can injure non- resistant soybeans. To try and prevent any misuses, Iowa has put major restrictions on dicamba applications. The biggest restriction is the special training that has been made mandatory for all applicators and distributors of dicamba.
As we promised you in last months dicamba article, keeping our community up to date on dicamba is a very high priority for us. All applicators and distributors of these herbicides must go through one of these trainings before they are licensed to apply any dicamba product for 2018. For more information and training dates, we encourage you to check out the Agribusiness Association of Iowa’s calendar.
Spring is just around the corner. Get the certification you need for the 2018 crop year before it is a race against time.