Overwatch® herbicide, from FMC, has officially been registered and will be available for the 2021 winter cropping season as a control for annual ryegrass and a wide range of other weeds.
FMC Herbicide Product Manager, Hugh Palmer, said the herbicide had been extensively trialled over many seasons and was now available as a pre-emergent option in wheat, barley and canola.
“This is a really unique herbicide,” he said. “Overwatch has control over Annual ryegrass and weeds such as silvergrass, bifora, sowthistle, hogweed and lesser loosestrife.”
He said Overwatch was initially assessed as an annual ryegrass product because of the concern regarding that weed in winter cropping regions throughout Australia
“It has outstanding annual ryegrass control and the fact that it effectively controls a wide range of other species is a real bonus.”
“There are a large number of weeds registered for suppression on the label so this herbicide will have an excellent fit in many paddocks,” he said.
“Overwatch also has long-lasting residual control making it very effective on later germinating weeds. Up to 12 weeks control of a wide range of species has been demonstrated.”
He said Overwatch is a Group Q herbicide, making it unique in the Australian broadacre market.
“Registration is very timely, as many of the weed species are developing resistance to commonly used herbicides.”
“The use of Overwatch in a winter crop system will help take the pressure off herbicides that are struggling with resistance. It also has the ability to control weeds that are no longer susceptible to other options.”
Mr Palmer said the unique mode of action certainly had growers and agronomists taking note as the ryegrass germinated and turned a bright magenta colour before perishing.
“Overwatch herbicide works by inhibiting the production of carotenoids in susceptible plants,” he said. “This, in turn, affects a plant's ability to produce energy through normal photosynthetic pathways. While the crop is able to metabolise the herbicide, the susceptible weeds use up available energy from the seed and then die.”
Overwatch is applied as an IBS (Incorporated By Sowing) treatment and has demonstrated its robust performance across a wide range of locations and conditions.
“Trials have been conducted across all the major winter crop areas of Australia and have included testing in a wide range of soil types, stubble loads and moisture conditions,” Mr Palmer said.
“The efficacy of Overwatch has been outstanding across the different environments. It has consistently demonstrated really good control of weeds.”
He said because Overwatch was registered in three key winter crops it provided greater options for crop rotations.
“Residual herbicides have been challenged with dry conditions in recent years so the introduction of Overwatch means growers can have more flexibility with the following crop.”
Crop safety was an important aspect of achieving registration and many trials have been conducted to demonstrate the ability of the crops to metabolise the herbicide and continue to grow.
“Some pre-emergent herbicides affect cell division and that may limit the crop’s root or plant growth,” Mr Palmer said.
“The effect is not seen in Overwatch and the only sign of the herbicide being metabolised is a transient bleaching of the crop.
“Discolouration is not common and is normally associated with higher doses of herbicide contacting the seed or plant directly.”
“Symptoms are negligible within weeks of the first appearance and the plants continue to actively grow throughout the process.”
The recommended application of Overwatch via Incorporated By Sowing (IBS) helps ensure the seed is placed sufficiently away from the herbicide.
Now that registration was achieved, FMC were producing good volumes of Overwatch herbicide in preparation for the 2021 season.
There are many trial sites throughout Australia in 2020 that are available for inspection by growers and agronomists.”
“I would encourage interested parties to have a look at the performance of this unique herbicide and see how suited it is to current farming practices,” Mr Palmer said.