THE AUSTRALIAN Pesticides and Veterinary Medicines Authority, the statutory body responsible for the registration of farm chemicals have highlighted the criteria the heavily scrutinised herbicide Overwatch needed to pass prior to gaining registration during its testing phase.
The new group Q, bixlozone-based herbicide, produced by FMC, has been under fire in its initial year of commercial use due to heavy levels of bleaching in crop sprayed with the crop, particularly in barley, and concerns about potential off-target crop damage.
A spokesperson for the APVMA said the authority had a set of statutory criteria it had to assess against when making decisions on whether to register chemicals and that Overwatch had passed each one.
The APVMA must consider safety, efficacy, potential international trade implications and labelling when making its decisions, along with ensuring human and animal safety and the environment are protected.
The spokesperson for the APVMA said Overwatch had been approved for the control of annual ryegrass and broadleaf weeds in wheat, barley and canola.
They said the product label describes how it should be used, including how and under what conditions it should be applied, and specifies mandatory downwind buffer zones to minimise the risks associated with spray drift, which has the potential to be one of the causes of the suspected off-target damage.
The spokesperson said the APVMA was aware of reports of crop damage related to the use of Overwatch and that the authority was working with the registrant and relevant state and territory authorities to understand the nature of these incidents.
Overwatch was a particularly eagerly anticipated release as it presented a new mode of action to control ryegrass, which is southern Australia's major problem weed which is becoming increasingly resistant to existing chemistries.
Agronomists are monitoring the situation, with some saying they hoped the bleaching effect, as bad as it looked, would prove to be mainly cosmetic and not have a major influence on yield and that the off-target impact is due to controllable spray drift rather than a highly volatile chemical composition.