Wheat and barley farmers have adopted a big shift in broadleaf weed control in 2020 with the ‘up-front’ use of the group H herbicide, CALLISTO®. While other group H formulations including TALINOR® have traditionally been used as a foliar spray in Australia, research supports the use of HPPD inhibitors (Group H) in earlier growth stages of target weeds.

“The level of HPPD resistance in weeds does change over the target’s lifecycle,” said Syngenta Resistance Research Technical Specialist Sarah-Jane Hutchings.

“This means if you were to use the same loading of a HPPD pre versus post, we expect to see better levels of control in the pre-emergent use pattern.”

CALLISTO utilises the active ingredient Mesotrione, which has benefited from decades of Syngenta research and development globally, ahead of its launch here. Resistant populations of Amaranthus in northern America have been a focus for Sarah and Syngenta for some years already.

“The enzymes that metabolise Mesotrione aren’t switched on until later in the plant’s lifecycle when the target weed is generally two to three inches [50 to 75mm] tall,” she said.  “The production of these enzymes is not switched on, or produced to a high enough level, very early in the target’s lifecycle to confer resistance.” 

CALLISTO can be applied prior to sowing in a knifepoint-press wheel system ahead of rainfall and is compatible with grass pre-emergents including BOXER GOLD®. Activated by rainfall, CALLISTO is primarily absorbed through the roots and translocated to the leaves.

Users have this year noted a tell-tale bleaching of young broadleaf weeds where they have emerged through CALLISTO treated soil. This discoloration of the plant pigments is symptomatic of interruption of photosynthesis.

“We’ve had some excellent feedback on CALLISTO in its first commercial year,” Syngenta Technical Services Lead James Considine said. “CALLISTO has really taken pressure off post-emergent broadleaf herbicide applications, which is huge for resistance management. We still want farmers to follow-up with that post-emergent application, but it is buying them a bit of time especially when they tend to be logistically challenged.”

Since CALLISTO is a group H, James said it was important that farmers and agronomists take this into account when building a suitable post-emergent strategy, utilising a ‘mix and rotate strategy’ along with other WeedSmart, Big 6 strategies.

“Whether farmers come back with a group B, C, F, G, I, O – or preferably a mix of two or more groups - these foliar sprays are in most cases (only) being asked to take care of the odd escape,” he said.

“This strategy will help prevent weed seed set and manage weed germinations not only this year but for years to come. Syngenta is a sponsor of WeedSmart and The Big 6, and we want to see greater adoption of these strategies so farmers are dictating terms, not weeds.”

Visit www.syngenta.com.au/callisto for the full list of weeds CALLISTO controls.