Overwatch™ Herbicide

Product Name: Overwatch® Herbicide

Active Constituent: Bixlozone (isoxazolidinone), powered by Isoflex™ active

Formulation Type: Suspension Concentrate (SC)

Proposed Use Rate: 1.25 L/Ha

Technical Highlights:

  • Long-lasting residual control of Annual ryegrass including herbicide resistant biotypes and regionally specific broadleaf weeds
  • New herbicide molecule - Group Q mode of action
  • Pre-emergent herbicide for application as an IBS (Incorporated By Sowing) treatment for use in Wheat, Barley and Canola

When will Overwatch® Herbicide be available?

Registration was approved by the APVMA in April 2020, and Overwatch® Herbicide will be available for the 2021 season.

How does Overwatch® Herbicide work?

As a group Q product, Overwatch®Herbicide inhibits susceptible plants from producing carotenoids. Carotenoids protect chlorophyll in plant cells and help in the photosynthetic process of the plant. While susceptible weeds are unable to metabolise Bixlozone and eventually die, tolerant crops will metabolise the product and continue growing.

This process relies upon the metabolic ability of the plants and therefore if a crop is not actively growing, crop discoloration may persist e.g. under cold, frosty conditions.

What is the crop safety of Overwatch® Herbicide?

Several years of Overwatch® Herbicide trial data in Australia has shown a high level of crop safety with little to no effect on vigour despite early discolouration of the crop.

There are many factors that affect the crop safety of all pre-emergent chemistry. These include the separation of seed from treated soil, correct sowing methods and using correct rates. The Overwatch® Herbicide label contains clear guidelines in this regard.  

Do you foresee any compatibility issues with Overwatch® Herbicide?

We are currently undertaking extensive compatibility work, and from the information gathered so far, we have not seen any issues with commonly used knockdown herbicides or relevant insecticides.

What is the incorporation time for Overwatch® Herbicide?

The Overwatch® Herbicide label recommends incorporation within three days of application.

Overwatch® Herbicide has low volatility.

Will Overwatch®Herbicide be recommended for use under disc seeding systems?

Overwatch® Herbicide is not recommended for use under disc seeding systems. This recommendation is due to the unreliable separation of seed and treated soil separation of these seeding systems.

The ‘soil throw’ component of knife point press wheel systems adds a greater level of crop safety by throwing treated soil out of the furrow.

What is the length of control expected from Overwatch®Herbicide?

While there are several different factors that affect the length of residual control, the chemical characteristics of Overwatch® Herbicide and trial data indicate equal or better control than other pre-emergent products on the market. Several field studies have demonstrated control up to 70 days after application.

These characteristics include relatively long half-life, low volatility and a moderate carbon binding capacity when compared to other pre-emergent herbicides.

What are the potential re-cropping issues of the product?

Due to the wide range of crops being investigated for Overwatch® Herbicide we do not perceive there to be any major re-cropping issues. This information will be stipulated on the label.

On the label, what weeds will Overwatch®Herbicide control?

  • Annual ryegrass (Lolium rigidum)
  • Silvergrass (Vulpia bromoides)
  • Bifora (Bifora testiculata)
  • Sowthistle (Sonchus oleraceus)
  • Hog weed/wireweed (Polygonum aviculare)
  • Lesser loosestrife (Lythrum hyssopifolia)

Efficacy can be variable according to climatic and soil conditions. Final use of the product should only be according to the approved label recommendations.

On the label, what weeds will Overwatch®Herbicide label suppress?

  • Barley grass (Hordeum murinum)
  • Wild oats (Avena fatua)
  • Brome grass (Bromus spp)
  • Phalaris (Phalaris paradoxa)
  • Bedstraw (Galium tricornutum)
  • Capeweed (Arctotheca calendula)
  • Prickly lettuce (Lactuca spp.)
  • Wild radish (Raphanus raphanistrum)

Efficacy can be variable according to climatic and soil conditions. Final use of the product should only be according to the approved label recommendations.

Will other crops and weeds be added to the label in the future?

FMC is currently investigating the potential use of Overwatch® Herbicide in several different crops, in different regions across Australia. Through this work we will also be identifying regionally specific weeds that may be added to the label.

How long is the grazing interval on the label?

The label states 12 weeks. However, feeding studies are currently underway to shorten this period so that Overwatch® Herbicide can be used in dual purpose grazing crops.
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