Dicamba is a benzoic acid herbicide that is used to control annual and perennial broadleaf weeds in grain crops and grasslands. Dicamba does not bind to soil particles and is highly soluble in water, which grants it high mobility in the soil with the possibility of contaminating groundwater. Also, it tends to spread from treated fields into neighboring fields, causing damage.
The aim of this study was to find organisms that are capable of degrading Dicamba, and at the same time, through a collaboration with Copenhagen University, see if those organisms are able to act as biological control agents against the fungal plant pathogen Fusarium culmorum.
A solid medium was devised that selects for pesticide degrading organisms, along with degradation experiments in liquid medium, which led to finding 4 bacterial species that can degrade the pesticide Dicamba.
Since the main purpose is to find the organisms that possess the dual function of pesticide degrader and biological control agent, those organisms that proved to be able to degrade the pesticide were used in sand assays with wheat seedlings, along with Fusarium culmorum, by coating the seeds first with the fungal pathogen and then the possible biocontrol agents. The setups were incubated for 2 weeks and then assessed depending on the severity of the symptoms caused by the Fusarium. At the same time, different concentrations of Dicamba were applied on wheat seed to determine if Dicamba could be included in the Fusarium sand assays, with the 6.25 mg/L concentration being chosen as a suitable working concentration.
Out of the organisms tested, none exhibited a dual function, while there are some organisms that were able to degrade Dicamba, those were not able to significantly decrease the symptoms caused by Fusarium culmorum on the wheat seedlings.